Computer graphics briefly. What is computer graphics and its types

As mentioned above, computer graphics can be divided into three main categories based on how images are described: raster, vector and three-dimensional graphics. Among two-dimensional graphics, pixel and fractal graphics stand out in a special way. 3D, CGI and infographics also require special consideration.

Pixel graphics

The term "pixel graphics" (from the English. pixel ) refers to a form of digital image created on a computer using a raster graphics editor, where the image is edited at the pixel (dot) level and the image resolution is so low that individual pixels are clearly visible.

There is a common misconception that any drawing made using raster editors is pixel art. This is not true pixel image differs from the usual raster technology - manual editing of the image pixel by pixel. Therefore, pixel art is characterized by its small size, limited color palette and (usually) lack of anti-aliasing.

Pixel graphics use only the simplest tools of raster graphics editors, such as Pencil, Straight (line) or Fill (fill with color). Pixel graphics are reminiscent of mosaics and cross-stitch or beadwork - since the design is made up of small colored elements, similar to the pixels of modern monitors.

Fractal graphics

A fractal is an object formed from irregular individual parts that are similar to the whole object. Since a more detailed description of smaller-scale elements occurs using a simple algorithm, such an object can be described with just a few mathematical equations.

Rice. 8.5.

Fractal graphics are indispensable when creating artificial mountains, clouds, and sea waves. Thanks to fractals, complex objects are easily depicted, the images of which are similar to natural ones. Fractals make it possible to describe entire classes of images, the detailed description of which requires relatively little memory (Fig. 8.5). On the other hand, fractals are poorly applicable to images outside of these classes.

3D graphics

Three-dimensional graphics (3D - from English 3 Dimensions – three dimensions) – three dimensions of the image) – a section of computer graphics, a set of techniques and tools (both software and hardware) designed to depict three-dimensional objects (Fig. 8.6).

Rice. 8.6.

3D image on a plane differs from a two-dimensional one in that it includes the construction of a geometric projection of a three-dimensional model of the scene onto a plane (for example, a computer screen) using specialized programs (however, with the creation and implementation 3D -displays and 3D -printers, three-dimensional graphics do not necessarily include projection onto a plane). In this case, the model can either correspond to objects from the real world (cars, buildings, hurricane, asteroid) or be completely abstract (projection of a four-dimensional fractal).

3D modeling is the process of creating a three-dimensional model of an object. Task 3D - modeling – to develop a three-dimensional image of the desired object. Using 3D graphics you can create exact copy a specific object, and develop a new, even unrealistic representation of an object that never existed.

Three-dimensional graphics operate with objects in three-dimensional space. Usually the results are a flat picture, a projection. Three-dimensional computer graphics widely used in television, cinema, computer games and printing products.

Three-dimensional graphics are actively used to create images on the plane of a screen or printed sheet in science and industry (for example, in design automation systems (CAD)); for creating solid elements: buildings, machine parts, mechanisms), architectural visualization (this also includes the so-called “virtual archeology”), in modern systems medical imaging.

3D graphics typically deal with virtual, imaginary, three-dimensional space that is displayed on the flat, two-dimensional surface of a display or piece of paper. Any image on the monitor, due to the plane of the latter, becomes raster, since the monitor is a matrix, it consists of columns and rows. Three-dimensional graphics exist only in our imagination - what we see on the monitor is a projection of a three-dimensional figure, and we ourselves create the space. Thus, graphics visualization can only be raster and vector, and the visualization method is only a raster (a set of pixels); the method of defining the image depends on the number of these pixels.

Currently, several methods are known for displaying three-dimensional information in volumetric form, although most of them represent volumetric characteristics very conditionally, since they work with a stereo image. From this area we can note stereo glasses, virtual helmets, 3D -displays capable of showing three-dimensional images.

-graphics

The term "CGI graphics" computer generated imagery stands for computer-generated images) refers to still and moving images generated by three-dimensional computer graphics and used in the visual arts, printing, cinematic special effects, television, and simulation. Computer games typically use real-time computer graphics, but CGI-based in-game videos are also occasionally added.

The creation of moving images is done by computer animation, which is a narrower area of ​​​​CGI graphics, also applicable in cinema, where it allows you to create effects that cannot be achieved using traditional makeup and animatronics. Computer animation can replace the work of stuntmen and extras, as well as scenery.

Infographics

The term "infographics" (from Lat. information awareness, explanation, presentation; and other Greek graphike - written, from grapho – I write) denote a graphical way of presenting information, data and knowledge.

The range of applications of infographics is huge - geography, journalism, education, statistics, technical texts. It helps not only to organize large amounts of information, but also to more clearly show the relationship of objects and facts in time and space, as well as demonstrate trends.

Infographics can be defined as any combination of text and graphics created with the intention of telling a story or conveying a fact. Infographics work where you need to show the structure and algorithm of something, the relationship of objects and facts in time and space, demonstrate a trend, show what something looks like, organize large amounts of information.

Infographics are a visual representation of information. Used where complex information needs to be presented quickly and clearly.

• Animatronics – a technique used in cinematography, animation, and computer modeling to create special effects for moving artificial parts of the human, animal, or other objects.

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Presentation of data on a computer monitor in graphical form was first implemented in the mid-50s for large computers used in scientific and military research. Since then, the graphical method of displaying data has become an integral part of the vast majority of computer systems, especially personal ones. The graphical user interface is the de facto standard for software today different classes, starting with operating systems.

There is a special field of computer science that studies methods and means of creating and processing images using software and hardware computing systems - computer graphics. It covers all types and forms of representation of images that are accessible to human perception either on a monitor screen or as a copy on an external medium (paper, film, fabric, etc.). Without computer graphics it is impossible to imagine not only computer, but also ordinary, completely material world. Data visualization is used in a variety of areas human activity. For example, let's name medicine (computed tomography), scientific research (visualization of the structure of matter, vector fields and other data), modeling of fabrics and clothing, and development projects.

Depending on the method of image formation, computer graphics are usually divided into raster, vector and fractal.

Figure 1 Figure 2 Figure 3

A separate item is considered three-dimensional (3D) graphics, studying techniques and methods for constructing three-dimensional models of objects in virtual space. As a rule, it combines vector and raster methods of image generation.

Features of the color gamut are characterized by such concepts as black and white and color graphics. The titles of some sections indicate specialization in individual areas: engineering graphics, scientific graphics, Web graphics, computer printing and others.

At the intersection of computer, television and film technologies, a relatively new field has emerged and is rapidly developing. computer graphics and animation.

Entertainment plays a prominent role in computer graphics. There was even such a concept as a mechanism for graphical presentation of data ( Graphics Engine). The gaming software market has a turnover of tens of billions of dollars and often initiates the next stage of improvement in graphics and animation.

Although computer graphics serves only as a tool, its structure and methods are based on the advanced achievements of fundamental and applied sciences: mathematics, physics, chemistry, biology, statistics, programming and many others. This remark is true for both software and hardware for creating and processing images on a computer. Therefore, computer graphics is one of the most rapidly developing branches of computer science and in many cases acts as a “locomotive” pulling the entire computer industry along with it.

Fractal graphics

Fractal graphics are based on mathematical calculations. The basic element of fractal graphics is the mathematical formula itself, that is, no objects are stored in the computer’s memory and the image is constructed exclusively using equations. In this way, both the simplest regular structures and complex illustrations that imitate natural landscapes and three-dimensional objects are built.

3D graphics

Three-dimensional graphics have found wide application in such areas as scientific calculations, engineering design, and computer modeling of physical objects (Fig. 3). As an example, let's consider the most complex version of three-dimensional modeling - creating a moving image of a real physical body.

In a simplified form, spatial modeling of an object requires:

· design and create a virtual frame (“skeleton”) of an object that most closely matches its real form;

· design and create virtual materials, the physical properties of the visualization are similar to real ones;

· assign materials to different parts of the surface of an object (in professional jargon - “project textures onto an object”);

· configure the physical parameters of the space in which the object will operate - set lighting, gravity, atmospheric properties, properties of interacting objects and surfaces;

· set the trajectories of movement of objects;

· apply surface effects to the final animation video.

To create a realistic model of an object, geometric primitives (rectangle, cube, ball, cone, etc.) and smooth, so-called spline surfaces. In the latter case, the method most often used is bicubic rational B-splines on a non-uniform mesh (NURBS). The appearance of the surface is determined by a grid of reference points located in space. Each point is assigned a coefficient, the value of which determines the degree of its influence on the part of the surface passing near the point. The shape and “smoothness” of the surface as a whole depends on the relative position of the points and the magnitude of the coefficients.

After forming the “skeleton” of the object, it is necessary to cover its surface with materials. The whole variety of properties in computer modeling comes down to visualizing the surface, that is, calculating the coefficient of transparency of the surface and the angle of refraction of light rays at the boundary of the material and the surrounding space.

Surface painting is carried out using Gouraud methods (Gouraud) or Phong (Phong). In the first case, the color of the primitive is calculated only at its vertices, and then linearly interpolated along the surface. In the second case, a normal to the object as a whole is constructed, its vector is interpolated along the surface of the component primitives, and lighting is calculated for each point.

The light leaving a surface at a particular point toward the observer is the sum of its components multiplied by a factor associated with the material and color of the surface at that point. These components include:

· light coming from the back side of the surface, that is, refracted light (Refracted);

· light uniformly scattered by the surface (Diffuse);

specularly reflected light (Reflected);

glare, that is, reflected light from sources (Specular);

· own surface glow (Self Illumination).

The next stage is the application (“projecting”) of textures to certain areas of the object’s frame. In this case, it is necessary to take into account their mutual influence at the boundaries of primitives. Designing materials for an object is a difficult task to formalize; it is akin to the artistic process and requires at least minimal creative abilities from the performer.

After completing the design and visualization of the object, they begin to “revive” it, that is, set the movement parameters. Computer animation is based on key frames. In the first frame, the object is set to its original position. After a certain period (for example, in the eighth frame), a new position of the object is set, and so on until the final position. Intermediate values ​​are calculated by the program using a special algorithm. In this case, not just a linear approximation occurs, but a smooth change in the position of the object’s reference points in accordance with the specified conditions.

These conditions are determined by the hierarchy of objects (that is, the laws of their interaction with each other), permitted planes of motion, maximum rotation angles, acceleration and speed values. This approach is called the method inverse kinematics of motion. It works well for modeling mechanical devices. In the case of imitation of living objects, the so-called skeletal models. That is, a certain frame is created, movable at points characteristic of the object being modeled. The movements of the points are calculated using the previous method. Then a shell consisting of modeled surfaces is superimposed on the frame, for which the frame is a set of control points, that is, it is created frame model. The wireframe model is rendered by overlaying surface textures based on lighting conditions. As the object moves, a very plausible imitation of the movements of living beings is obtained.

The most advanced animation method involves capturing the actual movements of a physical object. For example, bright light sources are attached to a person at control points and the specified movement is recorded on video or film. Then the frame coordinates of the points are transferred from the film to the computer and assigned to the corresponding reference points of the frame model. As a result, the movements of the simulated object are practically indistinguishable from the living prototype.

The process of calculating realistic images is called rendering(visualization). Most modern rendering programs are based on Backway Ray Tracing method. The use of complex mathematical models makes it possible to simulate physical effects such as explosions, rain, fire, smoke, fog. Once rendering is complete, 3D computer animation is used either as a standalone product or as individual parts or frames of the finished product.

A special area of ​​3D modeling in real time consists of simulators technical means– cars, ships, aircraft and spacecraft. They need to very accurately implement the technical parameters of objects and the properties of the surrounding physical environment. In simpler cases, for example, when learning to drive land vehicles vehicles, simulators are implemented on personal computers.

The most advanced devices to date have been created for training to pilot spaceships and military aircraft. Several specialized graphic stations built on powerful RISC-processors and high-speed video adapters with hardware accelerators for 3D graphics. General control of the system and calculation of interaction scenarios are entrusted to a supercomputer consisting of tens and hundreds of processors. The cost of such complexes is expressed in nine figures, but their use pays off quite quickly, since training on real devices is tens of times more expensive.

Raster graphics

For raster images consisting of dots, the concept is of particular importance permissions, expressing the number of points per unit length. It is necessary to distinguish between:

· original resolution;

· screen image resolution;

· resolution of the printed image.

Original resolution. Original resolution is measured in dpi ( dots per inch – dpi ) and depends on the requirements for image quality and file size, the method of digitizing and creating the original illustration, the selected file format and other parameters. In general, the rule applies: the higher the quality requirement, the higher the resolution of the original should be.

Screen resolution. For screen copies of an image, the elementary raster point is usually called pixel. Pixel size varies depending on the selected screen resolution(from the range of standard values), original resolution and display scale.

Monitors for image processing with a diagonal of 20–21 inches (professional class), as a rule, provide standard screen resolutions of 640x480, 800x600, 1024x768, 1280x1024, 1600x1200, 1600x1280, 1920x1200, 1920x1600 pixels. The distance between adjacent phosphor points on a high-quality monitor is 0.22–0.25 mm.

A resolution of 72 dpi is sufficient for a screen copy, 150–200 dpi for printing on a color or laser printer, and 200–300 dpi for output on a photo exposure device. A rule of thumb has been established that when printing, the resolution of the original should be 1.5 times greater than raster lineature output devices. In case the hard copy will be enlarged compared to the original, these values ​​should be multiplied by the scaling factor.

Resolution of a printed image and the concept of lineature. The dot size of a raster image both on a hard copy (paper, film, etc.) and on the screen depends on the method and parameters used rasterization original. When rasterizing, a grid of lines is superimposed on the original, the cells of which form raster element. The raster grid frequency is measured by the number lines per inch (Ipi) and is called lineature.

The raster dot size is calculated for each element and depends on the tone intensity in a given cell. The higher the intensity, the denser the raster element is filled. That is, if the cell contains absolutely black color, the size of the raster point will coincide with the size of the raster element. In this case, they talk about 100% occupancy. For a completely white color, the fill value will be 0%. In practice, element occupancy on a print usually ranges from 3 to 98%. In this case, all raster points have the same optical density, ideally approaching absolute black. The illusion of a darker tone is created by increasing the size of the dots and, as a result, reducing the white space between them with the same distance between the centers of the raster elements. This method is called rasterization amplitude modulation (AM).

Tone intensity(so-called lightness) It is customary to divide it into 256 levels. A larger number of gradations is not perceived by human vision and is redundant. A smaller number worsens the perception of the image (the minimum acceptable value for a high-quality halftone illustration is 150 levels). It is easy to calculate that to reproduce 256 tone levels it is enough to have a raster cell size of 256 = 16 x 16 pixels.

When outputting a copy of an image on a printer or printing equipment, the screen lineature is chosen based on a compromise between the required quality, the capabilities of the equipment and the parameters of the printed materials. For laser printers, the recommended lineature is 65-100 Ipi, for newspaper production - 65-85 lpi, for book and magazine printing - 85-133 lpi, for artistic and advertising work - 133-300 lpi.

When printing images with overlapping rasters, such as multicolor images, each subsequent raster is rotated by a certain angle. Traditional rotation angles for color printing are 105 degrees for cyan, 75 degrees for magenta, 90 degrees for yellow, and 45 degrees for black. In this case, the raster cell becomes oblique, and a resolution of 16x150=2400 dpi is no longer sufficient to reproduce 256 tone gradations with a lineature of 150 lpi. Therefore, for professional-class photographic exposure devices, a minimum standard resolution of 2540 dpi is adopted, which ensures high-quality rasterization at different raster rotation angles. Thus, the coefficient taking into account the correction for the raster rotation angle for color images is 1.06.

Dynamic range. The quality of tone image reproduction is usually assessed dynamic range (D). This optical density, numerically equal to the decimal logarithm of the reciprocal transmittance (for originals held up to the light, such as slides) or reflection coefficient(for other originals, such as printed prints).

For optical media that transmit light, the dynamic range ranges from 0 to 4. For surfaces that reflect light, the dynamic range value ranges from 0 to 2. The higher the dynamic range, the larger number halftones are present in the image and the better the quality of its perception.

The relationship between image parameters and file size. It is customary to use raster graphics to illustrate works that require high precision in the reproduction of colors and halftones. However, raster illustration file sizes grow rapidly as resolution increases. A photograph intended for home promotion (standard size 10x15 cm, digitized with a resolution of 200-300 dpi, color resolution 24 bits), occupies the format TIFF with compression mode enabled, about 4 MB. A slide digitized with high resolution occupies 45-50 MB. A separated color image in A4 format takes up 120-150 MB.

Scaling raster images. One of the disadvantages of raster graphics is the so-called pixelation images when enlarged (unless special measures are taken). Since the original contains a certain number of dots, then with a larger scale their size increases, raster elements become noticeable, which distorts the illustration itself (Fig. 4). To counteract pixelation, it is customary to digitize the original in advance with a resolution sufficient for high-quality visualization when scaling. Another technique is to use a stochastic raster to reduce the pixelation effect within certain limits. Finally, when scaling, the interpolation method is used, when the size of the illustration is increased not by scaling the points, but by adding the required number of intermediate points.

Figure 4 Pixelation effect when scaling a raster image

Vector graphics

If in raster graphics the basic element of the image is a dot, then in vector graphics it is line. A line is described mathematically as a single object, and therefore the amount of data to display an object using vector graphics is significantly less than in raster graphics.

Line – elementary object vector graphics. Like any object, a line has properties: shape (straight, curve), thickness, color, style (solid, dotted). Closed lines acquire the property filling. The space they cover can be filled with other objects (textures, maps) or the chosen color. The simplest open line is bounded by two points called nodes. Nodes also have properties whose parameters affect the shape of the end of the line and the nature of its connection to other objects. All other vector graphics objects are made up of lines. For example, a cube can be composed of six connected rectangles, each of which, in turn, is formed by four connected lines. It is possible to imagine the cube as twelve connected lines forming edges.

Mathematical foundations of vector graphics

Let's take a closer look at ways to represent various objects in vector graphics.

Dot. This object on the plane is represented by two numbers (x, y), indicating its position relative to the origin.

Figure 5 Vector graphics objects

Straight line. It corresponds to the equation y = kx + b . Specifying the parameters k And b, You can always display an infinite straight line in a known coordinate system, that is, two parameters are enough to specify a straight line.

Straight segment. It differs in that it requires two more parameters to describe it - for example, coordinates x 1 and X 2 beginnings and ends of the segment.

Second order curve. This class of curves includes parabolas, hyperbolas, ellipses, circles, that is, all lines whose equations contain degrees no higher than two. A second order curve has no inflection points. Straight lines are just a special case of second-order curves. Second order curve formula in general view might look like this, for example:

x 2 +a 1 y 2 +a 2 xy+a 3 x+a 4 y+a 5 =0.

Thus, to describe an infinite second-order curve, five parameters are sufficient. If you want to plot a curve segment, you will need two more parameters.

Third order curve. The difference between these curves and second-order curves is the possible presence of an inflection point. For example, the graph of a function at = x 3 has an inflection point at the origin (Fig. 15.5). It is this feature that makes it possible to make third-order curves the basis for displaying natural objects in vector graphics. For example, the bending lines of the human body are very close to third-order curves. All second-order curves, like straight lines, are special cases of third-order curves.

In general, the equation of a third-order curve can be written as follows:

x 3 +a 1 y 3 +a 2 x 2 y+a 3 xy 2 +a 4 x 2 +a 5 y 2 +a 6 xy+a 7 x+a 8 y+a 9 =0.

Thus, a third-order curve is described by nine parameters. The description of its segment will require two more parameters.

Figure 6 Third order curve (left) and Bezier curve (right)

Bezier curves. This is a special, simplified form of third-order curves (see Fig. 6). Bezier curve method (Bezier) is based on the use of a pair of tangents drawn to a line segment at its ends. Bezier curve segments are described by eight parameters, so it is more convenient to work with them. The shape of the line is affected by the angle of the tangent and the length of its segment. Thus, the tangents play the role of virtual “levers” with the help of which the curve is controlled.

Raster and vector graphics

Thus, choice raster or vector format depends on the goals and objectives of working with the image. If you need photographic color accuracy, then a raster is preferable. It is more convenient to present logos, diagrams, and design elements in vector format. It is clear that in both raster and vector representation, graphics (as well as text) are displayed on a monitor screen or printing device in the form of a collection of points. On the Internet, graphics are presented in one of the raster formats that browsers can understand without installing additional modules - GIF, JPG, PNG.

Without additional plugins (add-ons), the most common browsers only understand raster formats - .gif, .jpg and .png (the latter is not yet widely used). At first glance, the use of vector editors becomes irrelevant. However, most of these editors provide export to .gif or .jpg at the resolution you choose. And it is easier for novice artists to draw in vector media - if the hand trembles and the line goes in the wrong direction, the resulting element is easily edited. When drawing in raster mode, you risk irreparably damaging the background.

Due to the features of image representation described above, for each type you have to use a separate graphic editor - raster or vector. Of course they have common features– the ability to open and save files in different formats, use tools with the same names (pencil, pen, etc.) or functions (select, move, zoom, etc.), choose the desired color or shade... However, the principles implementation of drawing and editing processes different and are determined by the nature of the corresponding format. So, if in raster editors they talk about selecting an object, they mean a collection of points in the form of an area of ​​complex shape. The extraction process is very often labor-intensive and painstaking work. When you move such a selection, a “hole” appears. In a vector editor, an object represents a set of graphic primitives, and to select it, you just need to select each of them with the mouse. And if these primitives were grouped by the appropriate command, then it is enough to “click” once on any of the points of the grouped object. Moving a selected object exposes underlying elements.

However, there is a tendency towards rapprochement. Most modern vector editors are able to use raster images as backgrounds, or even convert parts of the image into vector format using built-in tools (tracing). Moreover, there are usually tools for editing the loaded background image, at least at the level of various built-in or installed filters. Version 8 of Illustrator is capable of loading Photoshop .psd files and using each of the resulting layers. In addition, to use the same filters, the generated vector image can be directly converted into a raster format and further used as an uneditable raster element. Moreover, all this is in addition to the usually available converters from vector to raster format with obtaining the corresponding file.

In computer graphics, at least three dozen file formats are used to store images. But only a part of them has become a “de facto” standard and is used in the vast majority of programs. As a rule, raster, vector, and three-dimensional image files have incompatible formats, although there are formats that allow you to store data of different classes. Many applications are focused on their own “specific” formats; transferring their files to other programs forces you to use special filters or export images to a “standard” format.

TIFF(Tagged Image File Format). The format is designed for storing high-quality raster images (file name extension.TIF). It is widely used and is portable across platforms. (IBM PC and Apple Macintosh), is supported by most graphics, layout and design programs. Provides a wide range of color gamuts - from monochrome black and white to 32-bit color separation model CMYK. Starting from version 6.0 in the format TIFF You can store information about masks (clipping paths) of images. Built-in compression algorithm is used to reduce file size LZW.

PSD(PhotoShop Document). Own format Adobe programs Photoshop (file name extension.PSD), one of the most powerful in terms of storage capabilities for raster graphic information. Allows you to remember the parameters of layers, channels, degrees of transparency, and many masks. 48-bit color encoding, color separation, and various color models are supported. The main disadvantage is that the lack of an effective information compression algorithm leads to a large volume of files.

PCX. The format appeared as a format for storing raster data in the PC PaintBrush program from Z-Soft and is one of the most common (file name extension.PCX). The inability to store color-separated images, insufficient color models and other limitations led to the loss of popularity of the format. Currently considered obsolete.

JPEG (Joint Photographic Experts Group). The format is intended for storing raster images (file name extension.JPG). Allows you to adjust the relationship between file compression ratio and image quality. The compression methods used are based on removing “redundant” information, so the format is recommended to be used only for electronic publications.

GIF (Graphics Interchange Format). Standardized in 1987 as a means of storing compressed images with a fixed (256) number of colors (file name extension .GIF). Gained popularity on the Internet due to its high compression ratio. Latest format version GIF89a allows you to load images interlaced and create images with a transparent background. Limited possibilities for the number of colors determine its use exclusively in electronic publications.

PNG (Portable Network Graphics). A relatively new (1995) format for storing images for publishing on the Internet (file name extension .PNG). Three types of images are supported - color with a depth of 8 or 24 bits and black and white with a gradation of 256 shades of gray. Information compression occurs with virtually no loss, 254 alpha channel levels and interlaced scanning are provided.

WMF (Windows MetaFile). Windows operating system vector image storage format (file name extension.WMF). By definition, it is supported by all applications of this system. However, the lack of tools for working with standardized color palettes accepted in printing and other shortcomings limit its use.

EPS (Encapsulated PostScript). A format for describing both vector and raster images in Adobe's PostScript language, the de facto standard in the field of prepress processes and printing (file name extension.EPS). Since the PostScript language is universal, the file can simultaneously store vector and raster graphics, fonts, clipping paths (masks), equipment calibration parameters, and color profiles. The format used to display vector content on the screen is W.M.F. and raster - TIFF. But the screen copy only roughly reflects the real image, which is a significant drawback EPS. The actual image can only be seen at the output of the output device, using special viewing programs or after converting the file to PDF format in the Acrobat Reader, Acrobat Exchange applications.

PDF (Portable Document Format). Document description format developed by Adobe (file name extension.PDF). Although this format is primarily intended for storing entire documents, its impressive capabilities allow for efficient presentation of images. The format is hardware-independent, so images can be displayed on any device - from a monitor screen to a photographic exposure device. A powerful compression algorithm with controls for the final image resolution ensures compact files with high quality illustrations.

In computer graphics the concept is used color resolution(another name is color depth). It defines a method for encoding color information for display on a monitor screen. To display a black and white image, two bits are enough (white and black). Eight-bit encoding allows you to display 256 gradations of color tone. Two bytes (16 bits) define 65,536 shades (this mode is called High Color). With a 24-bit encoding method, it is possible to define more than 16.5 million colors (the mode is called

From a practical point of view, the color resolution of the monitor is close to the concept color gamut. It refers to the range of colors that can be reproduced using one or another output device (monitor, printer, printing press, etc.). In accordance with the principles of image formation using additive or subtractive methods, methods have been developed for dividing a color shade into its constituent components, called color models. In computer graphics, models are mainly used RGB And H.S.B.(for creating and processing additive images) and CMYK(to print a copy of the image on printing equipment). Color models are located in a three-dimensional coordinate system forming color space, since from Grossman's laws It follows that color can be expressed as a point in three-dimensional space.

Grassmann's first law (law of three-dimensionality). Any color can be uniquely expressed by three components if they are linearly independent. Linear independence is the impossibility of obtaining any of these three colors by adding the other two.

Grassmann's second law (law of continuity). With a continuous change in radiation, the color of the mixture also changes continuously. There is no color that cannot be matched infinitely close.

Grassmann's third law (law of additivity). The color of a mixture of radiation depends only on its color, but not on its spectral composition. That is, the color ( WITH) mixture is expressed by the sum of color equations of radiation:

C 1 =R 1 R+G 1 G+B 1 B ;
C 2 =R 2 R+G 2 G+B 2 B;
C n =R n R+G n G+B n B;
C sums =(R 1 +R 2 +…+R n)R+(G 1 +G 2 +…+G n)G+ (B 1 +B 2 +…+B n)B.

CIE Lab color model

In 1920, the color spatial model was developed CIE Lab (Communication Internationale de I"Eclairage - international commission for the meeting. L, a, b– designations of coordinate axes in this system). The system is hardware independent and therefore is often used to transfer data between devices. In the model CIE Lab any color is determined by lightness (L) and chromatic components: parameter a, varying in the range from green to red, and parameter b, varying from blue to yellow. Model color gamut CIE Lab significantly exceeds the capabilities of monitors and printing devices, so before displaying the image presented in this model, it must be converted. This model was developed to harmonize color photochemical processes with printing processes. Today it is the default standard for Adobe Photoshop.

RGB color model

Color model RGB is additive, that is, any color is a combination in varying proportions of three primary colors - red (Red), green (Green) blue (Blue). It serves as the basis for the creation and processing of computer graphics intended for electronic reproduction (on a monitor, TV). When one component of the primary color is superimposed on another, the brightness of the total radiation increases. The combination of the three components gives an achromatic gray color, which, with increasing brightness, approaches white. At 256 gradation levels, black corresponds to zero values RGB and for white – maximum, with coordinates (255,255,255).

HSB color model

Color model H.S.B. designed with maximum consideration for the characteristics of human color perception. It is based on the Munsell color wheel. Color is described by three components: hue (Hue) saturation (Saturation) and brightness (Brigfitness). The color value is chosen as a vector emanating from the center of the circle. The dot in the center corresponds to the color white, and the dots along the perimeter of the circle correspond to pure spectral colors. The direction of the vector is specified in degrees and determines the color shade. The length of the vector determines the color saturation. On a separate axis called achromatic, brightness is set, with the zero point corresponding to black. Model color gamut H.S.B. covers everything known values real flowers.

Model H.S.B. It is customary to use it when creating images on a computer, simulating the working techniques and tools of artists. There are special programs that imitate brushes, pens, and pencils. Provides an imitation of working with paints and various canvases. After creating an image, it is recommended to convert it to a different color model, depending on how you intend to publish it.

CMYK color model, color separation

Color model CMYK refers to subtractive, and is used when preparing publications for printing. Color components CMY are the colors obtained by subtracting the primary ones from white:

cyan (cyan) = white - red = green + blue;

magenta = white - green = red + blue;

yellow = white - blue = red + green.

This method corresponds to the physical essence of the perception of rays reflected from printed originals. The colors cyan, magenta and yellow are called additional, because they complement the primary colors to white. This leads to the main problem of the color model. CMY – superimposing complementary colors on top of each other does not in practice produce pure black. Therefore, a pure black component was included in the color model. This is how the fourth letter appeared in the abbreviation of the color model CMYK (Cyan, Magenta, Yellow, blacK). To print on printing equipment, a color computer image must be divided into components corresponding to the components of the color model CMYK. This process is called color separation. The result is four separate images containing the same color content of each component in the original. Then, in a printing house, from forms created on the basis of color-separated films, a multi-color image is printed, obtained by overlaying colors CMYK.

Among the programs designed for creating computer two-dimensional painting, the most popular are Painter from Fractal Design, FreeHand from Macromedia, and Fauve Matisse. The Painter package has a fairly wide range of drawing and color tools. In particular, it simulates various tools (brushes, pencil, pen, charcoal, airbrush, etc.), allows you to imitate materials (watercolor, oil, ink), and also achieve the effect of a natural environment. In turn, the latest versions of the FreeHand program have rich image and text editing tools, contain a library of special effects and a set of tools for working with color, including multi-color gradient fill tools.

Among the image creation programs on the Macintosh platform, it is worth noting the bitmap painting and image editing package PixelPaint Pro from Pixel Resources.

Among computer painting programs for graphic stations Silicon Graphics(SGI) A special place is occupied by the StudioPaint 3D package from Alias ​​Wavefront, which allows you to paint with various tools (“brushes”) in real time directly on three-dimensional models. The package works with an unlimited number of image layers and provides 30 levels of undoing the previous action (undo), includes color correction operations and “spline brushes”, the “stroke” of which can be edited point by point like a spline curve. StudioPaint 3D supports a tablet with a sensitive pen, allowing the artist to sketch traditionally by hand, then transfer the drawing into 3D modeling or animation packages and build a 3D model from the sketch.

Adobe Photoshop

Adobe's Photoshop package occupies a special place in the broad class of programs for processing raster graphics. In fact, today it is the standard in computer graphics, and all other programs are invariably compared to it.

The main controls of Adobe Photoshop are located in the menu bar and toolbar. A special group consists of dialog boxes - tool palettes:

· The Brushes palette controls settings for editing tools. A brush enters editing mode after double-clicking on its image in the palette. CTRL-clicking destroys the brush. Double-clicking on a free field of the palette opens a dialog box for creating a new brush, which is automatically added to the palette.

· The Options palette is used to edit the properties of the current tool. You can open it not only from the menu bar, but also by double-clicking on the tool icon in the toolbar. The composition of the palette controls depends on the selected tool.

· The Info palette provides information support for display tools. It presents: the current coordinates of the mouse pointer, the size of the current selected area, the color parameters of the image element and other data.

· The Navigator palette allows you to view different parts of the image and change the viewing scale. The palette window contains a thumbnail of the image with a selected viewing area.

· The Synthesis palette displays the color values ​​of the current foreground and background colors. The sliders on the color bar of the corresponding color system allow you to edit these parameters.

· Palette Catalog contains a set of available colors. This set can be downloaded and edited by adding and removing colors. The color tone of the foreground and background is chosen from the set. The standard package of the program includes several color sets, mainly from Pantone.

· The Layers palette is used to control the display of all layers of the image, starting from the top one. It is possible to determine the parameters of layers, change their order, and operate on layers using different methods.

· The Channels palette is used to select, create, duplicate and delete channels, determine their parameters, change the order, convert channels into independent objects and form combined images from several channels.

· The Paths palette contains a list of all created paths. When you convert a path to a selection, it is used to form a clipping path.

· The Operations palette allows you to create macro commands – a given sequence of operations with the image. Macros can be recorded, executed, edited, deleted, or saved as files.

Filters represent a special group of image processing software. These are modules plugged into the program, often from third parties, that allow you to process an image according to a given algorithm. Sometimes such algorithms can be very complex, and the filter window can have many customizable parameters. Among the filter groups, products from the Kai's Power Tools, Alien Skin, Andromeda and others series are popular.

Currently, many illustrative graphics packages have been created that contain easy-to-use, developed and powerful vector graphics tools designed both for preparing materials for printing and for creating pages on the Internet.

To create a graphic object, you will need an illustrative vector graphics program. The quality and usefulness of vector graphics tools is determined primarily by their scaling capabilities.

Vector or illustration graphics packages have always been based on an object-oriented approach, allowing you to draw the outlines of objects and then fill them in with colors or patterns. You can reproduce these paths very accurately at any size because they are formed using a mathematical model of points and curves, rather than as raster images - a grid filled with rectangular pixels.

One of the new features we have discovered in this product category is multi-color gradient shading. Primitives such as polygons, stars, and spirals have become common features of such packages. Linked colors allow you to replace the rose's red with yellow, changing only the base color; all associated shades will change automatically. Multi-layered, interactive color "transparencies" provide previously unattainable depth, and you can convert vector images to raster images within a vector graphics file. While yesterday's vector graphics packages only allowed you to place a raster image into your file, today's programs allow you to embed raster images, resize them, and even apply special effects and masks. This facilitates the process of obtaining the final image using multilayer graphics - combining vector and raster files necessary to create logos, printed advertisements and images for the Web.

The principles behind the latest packages completely change the way we think about vector graphics. CorelXara 1.5 takes a completely new approach to visualization, with amazing tools for creating .GIF and JPEG output files and a phenomenally fast browser plug-in for working with vector graphics. Fractal Design's Expression 1.0 package allows you to construct paths from other complex vector graphics, giving you an endless variety of visual possibilities that are unattainable with other programs.

Unlike beginner-oriented desktop publishing software or photo editing programs, which typically contain the most commonly used editing tools, graphics packages for beginners tend to focus on specific tasks, such as diagramming or technical drawing. Acquiring the skills to freely draw Bezier curves is difficult even for a professional; It is no less difficult to master the basic principles of machine drawing, for example, the depiction of cuts and sections. In addition, many novice users do not understand the differences between raster and vector graphics and may not know when to use which packages. For these reasons, beginners should balance their goals with the program's capabilities and only upgrade to a full-featured painting package when they are ready.

In most cases, to create simple illustrations, it is enough for beginners to be able to work with the software tools that they may already have. Microsoft, Corel, and Lotus software packages contain drawing tools in their word processor and presentation graphics modules, as well as clipart libraries. In addition, AutoShape can create a large number of standard shapes and even diagramming symbols (which can cast shadows or even be extruded to give them three-dimensionality), and the WordArt gallery provides interesting and colorful text styles that you can use to can be used for headings or labels.

For technical tasks, let's pay attention to such diagramming programs as FlowCharter 7 from Micrografx (http://www.micrografx.com) or Visio Professional 4.5 from Visio Corp. (http://www.visio.com). If you start working in the field of CAD, then there are several packages that are quite affordable in price and capabilities, including AutoCAD LT from Autodesk (http://www.autodesk.com) or Design CAD from ViaGrafx (http://www.viagrafx .com).

To prepare drawings for small construction projects, such as a home remodel or kitchen remodel, you can use Planix and Draftix packages from SoftDesk (http://www.softdesk.com), Visual Home from Books That Work (www.btw.com), or 3D Home Architect, Edition 2 by Broderbund Software (http://www.broderbund.com/3dhome).

Corel Draw 8-9

CorelDraw always makes a strong impression. Corel included many programs in the kit, including Corel Photo-Paint. The new package has undoubtedly the most powerful tools among all survey programs, and at the same time, compared to the previous version, the interface has become simpler, and the tools for drawing and editing nodes are more flexible (Fig. 9). However, when it comes to new functions, in particular preparing publications for the Web, here CorelDraw is inferior to CorelXara. CorelDraw's work with CMYK colors leaves much to be desired. The colors in the GIF and JPEG files were noticeably different from the Matchprint proof, while FreeHand produced the same colors on screen, in Web files, and in printers.

No problem. CorelDraw's artistic text design capabilities are impeccable, and the default settings for letter spacing when placing text along a curve do not require settings to prevent letter overlap - unlike Canvas and FreeHand. The magnifying glass tool is unrivaled - it allows you to get many special effects, including the ability to enlarge only a portion of the image and automatic settings text colors depending on the background color.

You can crop images, apply color filters, and give raster images the appearance of a curved page using 2D and 3D effects and PhotoShop plug-ins. When you needed to edit pixels, CorelDraw automatically switched you to Corel Photo-Paint, where you could edit the file and save it directly in CorelDraw. However, beyond basic scaling and dynamic sizing capabilities, CorelDraw does not include special tools for preparing technical illustrations, like Smart Mouse in Canvas or copying arrays in Designer.

Not everything is so smooth. The ability to implement CMYK models - an area CorelDraw has struggled with - is still a concern, although the program can now work with Kodak's CMS color management system. First, to maintain compatibility with previous versions of CorelDraw, you need to turn off Kodak color correction every time you open CorelDraw in the View menu. Second, unless your printers are on the limited list of approved peripherals, there is no guarantee that a matching generic driver will always be available. CorelDraw exports colors the same way they appear when color correction is turned off, so to get a good image on a Web page, it is best to select the oversampling mode when exporting raster files. Corel viewer. CMX is painfully slow, and CMX files are larger than CDR files, which is a big deal when working on the Web. Barista, Corel's Java-based format for displaying documents on the Web, is a promising technology, but currently it's best used only for simple documents.

Despite its powerful tools, CorelDraw suffers from certain shortcomings. CorelDraw's wide range of tools makes it exceptionally useful for drawing, but the unnatural appearance of printed pages and Web pages limits its use. If you want to get the most out of CorelDraw, we recommend waiting for the next version, regularly checking the Corel Web site for new releases, and starting with a phone call to technical support to ensure your color correction settings are correct.

Micrografx Designer 7

Micrografx Designer 7, an easy-to-use, albeit small program that handled most tests with ease, also deserves special mention for its excellent technical illustration tools. Designer 7, along with FlowCharter 7 and Picture Publisher 7, forms the core of the Micrografx Graphics Suite and is one of the least expensive programs in this review. Designer's drawing tools are some of the easiest to learn and use. Like CorelXara, Designer doesn't have a text editing window, forcing you to constantly edit it in full WYSIWYG mode. Moving between layers is very awkward and although you can use multiple pages of different formats, moving objects between pages requires an editing buffer.

Powerful tools. The unique Reference Point tool allows you to set restrictions on x- and y-axis distances and rotation angles, or force all objects to be placed at a certain distance from a certain point. Designer 7 has many features—like iterative color mixing—not found in previous versions, but we still found a few major shortcomings. Snapping to guides only occurred when resizing an object, not when dragging it.

However, the Designer package comes with some interesting raster filters and effects, and it allowed us to edit pixels in Picture Publisher using OLE technology. Designer produced good GIFs with color blending, GIFs without color blending with images that resembled wicker baskets, and abnormal JPEGs with images that looked like bubbles. Designer also allows you to attach URLs to objects for use with the Micrografx QuickSilver 3 browser plug-in. What makes QuickSilver special is that you can assign specific properties to vector graphics objects. Designer 7's simple interface makes it easy to handle many typical office graphics jobs, but fundamental tool limitations and very limited capabilities for four-color CMYK printing may discourage professional graphic artists from purchasing it. But if you need powerful tool For technical drawing or you want to work interactively and post materials on your Web pages without programming, then perhaps you should opt for this package.

Adobe Illustrator 7

Adobe Systems has finally introduced the next version of its Adobe Illustrator 7.0 package. The new version is one of the most expensive among standalone programs vector graphics discussed in this review. Illustrator's functionality today is so inferior to CorelDraw, not to mention Macromedia FreeHand 7, that we wouldn't recommend it for professional graphic artists until Adobe releases a substantially modernized version. Figure 10 shows the documents window in this editor.

Glorious past. A veteran of vector graphics, Illustrator was once a towering achievement in the field and served as the model on which all the programs presented in this review are based. But since then, every new product has had some improvement. For example, Macromedia FreeHand does a better job of importing EPS and AI files while maintaining the high CMYK color accuracy that Illustrator has always had. CorelDraw has long raised the bar with gradient shading, true layers, Boolean operations, and special effects in its packages. Canvas 5 features pixel-level raster image editing and a workspace of nearly 140 m2, compared to Illustrator's 0.2 m2 workspace. Micrografx Designer provides superior drawing tools, integrates with Windows and Microsoft Office, and includes tools for preparing technical illustrations, while CorelXara provides true transparency for vector objects and the ability to embed raster images. In turn, Fractal Design Expression using the Skeletal Strokes tool allows you to obtain the most unusual effects and modify the image.

Unfortunately, Illustrator's relatively limited feature set doesn't mean it's easy to use. It's estimated that a gradient shading of a rainbow image that requires 5 clicks in CorelDraw would take 67 clicks in Illustrator because you'll have to create transitions for each pair primary colors.

Basic tools. Illustrator does not allow you to export .GIF and JPEG files for use on the Web. And while color print quality remains Illustrator's biggest strength, you'll love FreeHand's CMYK color processing capabilities just as much (and the same version of FreeHand can run on both Windows and Mac). There are also issues to be aware of when using Illustrator with S3-based graphics cards (Adobe warns users about this). Illustrator, which at one time paved the way for other graphics packages, has faded into the background today. Until Adobe seriously redesigns it, we recommend looking elsewhere. If you're still working in Illustrator and files created with it, consider FreeHand as an alternative.

Macromedia FreeHand 7

Macromedia FreeHand 7 impresses with impeccable quality of screen output and four-color CMYK printing and the availability of several formats for the Web. Because FreeHand always displays colors as they will appear when printed, it was the only program in our review that did not allow the creation or assignment of colors that would be very different when printed from the corresponding colors on the screen. The FreeHand color listing only includes colors that you have used or created. The program allows you to select colors from several libraries, including Pantone and Hexachrome for printing, and from the Web palette, optimized for both Mac and PC.

FreeHand's tools for drawing and working with text meet the necessary requirements, but are somewhat limited. The FreeHand interface favors editing nodes rather than editing the entire object. Each of the operations of scaling, rotating, mirroring and warping - performed in CorelDraw by manipulation in the object's working window - requires a separate tool from the FreeHand toolkit. When you select an object, its points (nodes) are always available for direct editing, but this means that you see the nodes and paths of the object, and not its “finished” view.

Corel Xara 1.5

Working with CorelXara is like sitting behind the wheel of an elegant red Ferrari convertible in a beautiful spring park. The simple and clear interface of CorelXara will first of all make you wonder: why is it considered that using illustrative graphics packages is so difficult?

CorelXara 1.5 is one of the new generation programs discussed in this review. It serves primarily to create a graphic image on a page at a time and form a block of text at a time. The program allows you to do things you could only dream of with drawings, gradient fills, images and transparencies. Although Corel advertises CorelXara 1.5 as a complement to CorelDraw 7 for creating Web graphics, CorelXara's inherent performance, Web capabilities, and specialized tools are superior to CorelDraw in many ways.

With the scaling capabilities of vector graphics and raster image textures, 2D objects begin to look more and more like 3D objects. Draw the object. Apply a texture (bitmap) or paint over it (material). Determine the level of transparency. Then move the image and edit it to your liking.

What is behind the external simplicity. CorelXara's interface is elegant and simple. Icons in the top row provide access to full-color visual sets of colors, fills, shading, bitmaps, fonts, and graphic inserts (cliparts).

CorelXara makes it easy to manage color by creating families of related shades. Change the base color from blue to green and your subject changes the entire gamut of hues. Note that CorelXara does not include specific tools for technical illustration, and you must enter the text yourself because CorelXara does not provide import filters for word processing programs. However, this program was the only one reviewed that allowed you to place multiple lines of text along one curved guide, and its collection of fonts not only contains their names, but also shows the typefaces.

We offer a summary table of the main characteristics of the most popular programs for working with vector graphics:

Miracles for the Web. Today's most powerful Web graphics tool, the CorelXara plug-in for Netscape Navigator and Microsoft Internet Explorer, allows you to zoom in up to 25,000% directly from the browser. Thanks to file compactness and high performance, vector graphics offer bright prospects in the field of Web page development.

CorelXara can't do it all, but in some ways it's unrivaled. If you prepare complex original designs, are just getting started with art packages, or enjoy working with transparent layers, CorelXara is a good addition to your toolbox.

We offer a summary table of the main characteristics of the most popular programs for working with vector graphics.

	Adobe Illustrator	Canvas 5	Corel Draw	CorelXara 1.5	Fractal Design Expression	Macromedia FreeHand 7	Micrografx Designer 7
functionality
artistic illustration	acceptable	acceptable
technical illustration
color printing					acceptable
preparing web pages					acceptable
ease of use
artistic illustration		acceptable
technical illustration
color printing
preparing web pages
working with color
color models			CIE lab CMY CMYK HSB HSL RGB YIQ

Category artistic illustration characterizes the diversity and versatility of drawing tools. In addition, software products must be able to accurately import and export a variety of file types.

Category color printing reflects the software's color matching capabilities and the quality of the resulting prints. Illustrative graphics programs must identify areas where color pairs meet, perform spot color conversions to process colors, and precise color separations.

On personal computers, three packages occupy the main market share of 3D graphics processing software. They work most efficiently on the most powerful machines (two- or four-processor Pentium II/III, Xeon configurations) running the Windows NT operating system.

The Kinetix 3D Studio Max program for creating and processing three-dimensional graphics was originally created for the Windows platform. This package is considered “semi-professional”. However, its resources are quite sufficient for developing high-quality three-dimensional images of inanimate objects. Distinctive features of the package are support for a large number of 3D graphics hardware accelerators, powerful lighting effects, and a large number of add-ons created by third-party companies. The comparative undemanding nature of hardware resources allows it to work even on mid-range computers. At the same time, in terms of modeling and animation, the 3D Studio Max package is inferior to more developed software.

Microsoft's Softimage 3D was originally designed for workstations. SGI and only relatively recently was converted into an operating room Windows system N.T. The program is distinguished by rich modeling capabilities and the presence of a large number of adjustable physical and cinematic parameters. A high-quality and fairly fast Mental Ray module is used for rendering. There are many add-ons released by third parties that significantly expand the functionality of the package. This program is considered the “de facto” standard in the world of specialized graphics stations SGI, and on the platform IBM PC looks a little heavy and requires powerful hardware resources.

The most revolutionary in terms of interface and capabilities is the Maua program, developed by a consortium of well-known companies (Alias, Wavefront, TDI). The package exists in versions for different operating systems, including Windows NT. Maua's tools are divided into four groups: Animation (animation), Modeling (modeling), Dynamic (physical modeling), Rendering (visualization). A convenient, customizable interface is made in accordance with modern requirements. Today Maua is the most advanced package in the class of tools for creating and processing 3D graphics for personal computers.

All areas of application - be it engineering and science, business and art - are the scope of computer graphics. The growing potential of PCs and their sheer number of approximately 100 million PCs provides a tempting base for investment and growth. It is unknown how long the trend of capital investment doubling will last, especially driven by prices, but a steady 10% annual increase is expected over the next 5 years. Today, companies specializing in graphical user interfaces, object-oriented programs, virtual reality and parallel process software are especially attractive to investors.

According to the increase in the number of graphic terminals from 100 in 1964 to 50,000 in 1977, and already in 1994, 3 million workstations and 60 million PCs are used in the USA alone. Computer graphics today has an industrial base estimated at $36 billion, which provides jobs for about 300 thousand specialists. It continues to lead the way in how we interact with computers and access information. We are entering new era empowering graphics systems when moving along the information superhighway.

1. Computer Science: Basic Course/S.V. Simonovich and others - St. Petersburg: “Peter”, 2001.
2. Systems and means of informatics: Issue 4. – M.: “Nauka”, 1993.
3. Informatics: Workshop on computer technology / edited by I.V. Makarova. – 2nd edition. – M.: “Finance and Statistics”, 1998.
4. Lavel. Graphics. Raster and vector graphics: http://win-www.klax.tula.ru/~level/graphics/predgrph.html
5. Vector graphics: http://imped.vgts.ru/polygraph/vektor.html
6. About vector and raster graphics: http://flashmaker.8m.com/help/html/02basics2.html

There are methods for calculating procedural effects (Procedural Effects) and the interaction of particle systems (Particle System). However, their full use requires enormous computing resources, and therefore simplified versions are usually used in personal computers.

This review is based on software as of 1999; subsequent versions are not included in the review.

N/A - not applicable. This product does not provide this capability.

Object from the ClipArt collection

Computer graphics is a branch of computer science that studies the means and methods of creating and processing graphic images using computer technology. Despite the fact that to work with computer graphics There are many classes of software; there are four types of computer graphics. This raster graphics, vector graphics, three-dimensional and fractal graphics. They differ in the principles of image formation when displayed on a monitor screen or when printed on paper.

Raster graphics are used in the development of electronic (multimedia) and printed publications. Illustrations made using raster graphics are rarely created manually using computer programs. Most often, scanned illustrations prepared by the artist on paper or photographs are used for this purpose. Recently, digital photo and video cameras have found widespread use for inputting raster images into a computer. Accordingly, most graphic editors designed for working with raster illustrations are focused not so much on creating images, but on processing them. On the Internet, raster illustrations are used in cases where it is necessary to convey the full range of shades of a color image.

Software tools for working with vector graphics, on the contrary, are intended primarily for creating illustrations and, to a lesser extent, for processing them. Such tools are widely used in advertising agencies, design bureaus, editorial offices and publishing houses. Design work based on the use of fonts and simple geometric elements is much easier to solve using vector graphics. There are examples of highly artistic works created using vector graphics, but they are the exception rather than the rule, since the artistic preparation of illustrations using vector graphics is extremely complex.

Three-dimensional graphics are widely used in engineering programming, computer modeling of physical objects and processes, animation, cinematography and computer games.

Software tools for working with fractal graphics are designed to automatically generate images through mathematical calculations. Creating a fractal artistic composition is not about drawing or design, but about programming. Fractal graphics are rarely used to create printed or electronic documents, but they are often used in entertainment programs.

Raster graphics

The main (smallest) element of a raster image is dot. If the image is on-screen, then this point is called pixel. Each pixel in a raster image has properties: placement and color. The higher the number of pixels and the smaller their sizes, the better the image looks. Large amounts of data are a major challenge when using raster images. Active work with large-sized illustrations such as magazine strips requires computers with exceptionally large amounts of RAM (128 MB or more). Of course, such computers must also have high-performance processors. The second disadvantage of raster images is that they cannot be enlarged to view details. Since the image consists of dots, enlarging the image only causes the dots to become larger and resemble a mosaic. It is not possible to see any additional details when enlarging the raster image. Moreover, increasing the raster dots visually distorts the illustration and makes it rough. This effect is called pixelation.

Vector graphics

Just as in raster graphics the main element of the image is a point, so in vector graphics the main element of the image is line(it doesn’t matter whether it’s a straight line or a curve). Of course, there are also lines in raster graphics, but there they are considered as combinations of points. For each line point in raster graphics, one or more memory cells are allocated (the more colors the points can have, the more cells are allocated to them). Accordingly, the longer the raster line, the more memory it takes up. In vector graphics, the amount of memory occupied by a line does not depend on the size of the line, since the line is represented as a formula, or more precisely, in the form of several parameters. Whatever we do with this line, only its parameters stored in memory cells change. The number of cells remains unchanged for any line.
A line is an elementary vector graphics object. Everything in a vector illustration is made up of lines. The simplest objects are combined into more complex ones, for example, a quadrilateral object can be thought of as four connected lines, and a cube object is even more complex: it can be considered either twelve connected lines or six connected quadrilaterals. Because of this approach, vector graphics are often called object-oriented graphics. We said that vector graphics objects are stored in memory as a set of parameters, but we must not forget that all images are still displayed on the screen in the form of dots (simply because the screen is designed that way). Before displaying each object on the screen, the program calculates the coordinates of screen points in the object's image, which is why vector graphics are sometimes called calculated graphics. Similar calculations are made when outputting objects to a printer. Like all objects, lines have properties. These properties include: line shape, thickness, color, character of the line(solid, dotted, etc.). Closed lines have the property of filling. The inner area of ​​the closed loop can be filled with color, texture, map. The simplest line, if it is not closed, has two vertices, which are called nodes. Nodes also have properties that determine how the top of a line looks and how two lines connect to each other.

Fractal graphics

A fractal is a pattern that consists of elements that are similar to each other. There are a large number of graphic images that are fractals: the Sierpinski triangle, the Koch snowflake, the Harter-Haithway “dragon”, the Mandelbrot set. The construction of a fractal pattern is carried out using some kind of algorithm or by automatically generating images using calculations using specific formulas. Changing values ​​in algorithms or coefficients in formulas leads to modifications of these images. The main advantage of fractal graphics is that only algorithms and formulas are saved in the fractal image file.

3D graphics

Three-dimensional graphics (3D graphics) studies techniques and methods for creating three-dimensional models of objects that closely resemble real ones. Such three-dimensional images can be rotated and viewed from all sides. To create three-dimensional images, various graphic shapes and smooth surfaces are used. Using them, the frame of an object is first created, then its surface is covered with materials that are visually similar to real ones. After this, lightening, gravity, atmospheric properties and other parameters of the space in which the object is located are done. For moving objects, indicate the trajectory of movement and speed.

Basic concepts of computer graphics

In computer graphics, the concept of resolution tends to be the most confusing, since we have to deal with multiple properties of different objects at once. It is necessary to clearly distinguish between: screen resolution, printing device resolution and image resolution. All these concepts refer to different objects. These types of resolutions are in no way related to each other until you need to know what physical size the picture on the monitor screen, print on paper or file on the hard drive will have.
Screen resolution is a property of the computer system (depending on the monitor and video card) and the operating system (depending on Windows settings). Screen resolution is measured in pixels (dots) and determines the size of the image that can fit entirely on the screen.
Printer resolution is a property of the printer that expresses the number of individual dots that can be printed on an area unit length. It is measured in units of dpi (dots per inch) and determines the size of an image at a given quality or, conversely, the quality of an image at a given size.
Image Resolution is a property of the image itself. It is also measured in dots per inch - dpi and is set when creating an image in a graphics editor or using a scanner. So, to view an image on the screen, it is enough that it has a resolution of 72 dpi, and for printing on a printer - no less than 300 dpi. The image resolution value is stored in the image file.
Physical Image Size determines the size of the picture vertically (height) and horizontally (width); it can be measured both in pixels and in units of length (millimeters, centimeters, inches). It is set when the image is created and is stored with the file. If an image is being prepared for display on a screen, then its width and height are specified in pixels in order to know how much of the screen it occupies. If an image is being prepared for printing, then its size is specified in length units in order to know how much of the sheet of paper it will occupy.
Physical size and image resolution are inextricably linked. When you change the resolution, the physical size automatically changes.

When working with color, the following concepts are used: color depth (also called color resolution) and color model.
A different number of bits can be allocated to encode the color of an image pixel. This determines how many colors can be displayed on the screen at the same time. The longer the binary color code is, the more colors can be used in the design. Color depth is the number of bits that are used to encode the color of one pixel. To encode a two-color (black and white) image, it is enough to allocate one bit to represent the color of each pixel. Allocation of one byte allows you to encode 256 different colors. Two bytes (16 bits) allow you to define 65536 different colors. This mode is called High Color. If three bytes (24 bits) are used to encode color, 16.5 million colors can be displayed simultaneously. This mode is called True Color. The size of the file in which the image is saved depends on the color depth.

Colors in nature are rarely simple. Most color shades are formed by mixing primary colors. The method of separating a color shade into its component components is called color model. There are many various types color models, but in computer graphics, as a rule, no more than three are used. These models are known under the names: RGB, CMYK, HSB.

RGB color model

The RGB model is the easiest to understand and most obvious. This model works with monitors and household TVs. Any color is considered to consist of three main components: red (Red), green (Green) and blue (Blue). These colors are called primary.

It is also believed that when one component is superimposed on another, the brightness of the total color increases. The combination of the three components gives a neutral color (gray), which tends to white at high brightness. This corresponds to what we see on the monitor screen, so this model is always used when preparing an image intended to be reproduced on the screen. If the image undergoes computer processing in a graphics editor, then it should also be presented in this model.

The method of obtaining a new hue by summing the brightness of the constituent components is called additive method. It is used wherever a color image is viewed in transmitted light (“through transmission”): in monitors, slide projectors, etc. It is not difficult to guess that the lower the brightness, the darker the shade. Therefore, in the additive model, the central point, which has zero component values ​​(0,0,0), has a black color (no glow of the monitor screen). White color matches maximum values components (255, 255, 255). The RGB model is additive, and its components: red (255,0,0), green (0,255,0) and blue (0,0,255) are called primary colors.

CMYK color model

This model is used to prepare printed images rather than screen ones. They differ in that they are seen not in transmitted light, but in reflected light. The more ink you put on the paper, the more light it absorbs and the less it reflects. The combination of the three primary colors absorbs almost all the incident light, and from the outside the image looks almost black. Unlike the RGB model, increasing the amount of paint does not lead to an increase in visual brightness, but rather to its decrease.

Therefore, to prepare printed images, not an additive (summing) model is used, but subtractive (subtractive) model. The color components of this model are not the primary colors, but those resulting from subtracting the primary colors from white:
blue (Cyan)= White - red = green + blue (0,255,255)
purple (lilac) (Magenta)= White - green = red + blue (255,0,255)
yellow= White - blue = red + green (255,255,0)
These three colors are called additional, because they complement the primary colors to white.
A significant difficulty in printing is the color black. Theoretically, it can be obtained by combining three primary or additional colors, but in practice the result turns out to be unsuitable. Therefore, a fourth component has been added to the CMYK color model - black. This system owes the letter K in its name (blacK) to him.

In printing houses, color images are printed in several stages. By placing cyan, magenta, yellow and black prints on paper in turn, a full-color illustration is obtained. Therefore, the finished image obtained on a computer is divided into four components of a single-color image before printing. This process is called color separation. Modern graphic editors have tools to perform this operation.
Unlike the RGB model, the center point is white (no dyes on white paper). To the three color coordinates a fourth has been added - the intensity of the black paint. The black axis looks isolated, but that makes sense: when you add the colored components to black, you still get black. Anyone can check the addition of colors in the CMYK model by picking up blue, gray and yellow pencils or felt-tip pens. A mixture of blue and yellow on paper gives green, purple with yellow - red, etc. When all three colors are mixed, the result is an indeterminate dark color. Therefore, in this model black color was needed additionally.

HSB color model

Some graphic editors allow you to work with the HSB color model. If the RGB model is most convenient for computers, and the CMYK model is most convenient for printing houses, then the HSB model is most convenient for humans. It is simple and intuitive. The HSB model also has three components: hue of color (Hue), color saturation (Saturation) And color brightness (Brightness). By adjusting these three components, you can create just as many random colors as with other models. The hue of a color indicates the number of a color in the spectral palette. Color saturation characterizes its intensity - the higher it is, the “purer” the color. The brightness of a color depends on the addition of black to a given color - the more it is, the less brightness the color is.

The HSB color model is convenient for use in those graphic editors that are focused not on processing ready-made images, but on creating them with your own hands. There are programs that allow you to simulate various artist tools (brushes, pens, felt-tip pens, pencils), paint materials (watercolor, gouache, oil, ink, charcoal, pastel) and canvas materials (canvas, cardboard, rice paper, etc.). When creating your own artwork, it is convenient to work in the HSB model, and once finished, it can be converted to an RGB or CMYK model, depending on whether it will be used as screen or printed illustration. The color value is chosen as a vector extending from the center of the circle. The dot in the center represents white (neutral) color, and the dots around the perimeter represent pure colors. The direction of the vector determines the color shade and is specified in the HSB model in angular degrees. The length of the vector determines the color saturation. Color brightness is set on a separate axis, the zero point of which is black.

Graphic formats

Any graphic image is saved in a file. The way graphic data is laid out when it is saved in a file determines the file's graphic format. There are file formats for raster images and vector images.
Raster images are saved in a file in the form of a rectangular table, in each cell of which the binary color code of the corresponding pixel is written. Such a file stores data about other properties of the graphic image, as well as its compression algorithm.
Vector images are saved in a file as a list of objects and the values ​​of their properties - coordinates, sizes, colors, etc.
There are quite a large number of both raster and vector graphic file formats. Among this variety of formats, there is no ideal one that would satisfy all possible requirements. The choice of one or another format for saving an image depends on the goals and objectives of working with the image. If photographic accuracy of color reproduction is needed, then preference is given to one of the raster formats. It is advisable to store logos, diagrams, and design elements in vector formats. The file format affects the amount of memory the file occupies. Graphic editors allow the user to independently choose the format for saving the image. If you are going to work with a graphic image in only one editor, it is advisable to choose the format that the editor offers by default. If the data will be processed by other programs, it is worth using one of the universal formats.
There are universal graphics file formats that simultaneously support both vector and raster images.
Format PDF(English: Portable Document Format) is designed to work with the Acrobat software package. In this format, images in both vector and raster formats, text with a large number fonts, hypertext links and even printer settings. The file sizes are quite small. It only allows viewing files; editing images in this format is not possible.
Format EPS(English: Encapsulated PostScript - encapsulated postscript) - a format that is supported by programs for different operating systems. Recommended for printing and creating illustrations in desktop publishing systems. This format allows you to save a vector outline that will delimit the raster image.

Raster graphics file formats

There are several dozen raster image file formats. Each of them has its own positive qualities, which determine the advisability of its use when working with certain programs. Let's look at the most common of them.
A fairly common format is Bitmap(English: Bit map image - image bit map). Files in this format have the extension .BMP. This format is supported by almost all raster graphics editors. The main disadvantage of the BMP format is the large file size due to the lack of compression.
The format is used to store multi-color images JPEG(eng. Joint Photographic Expert Group - a joint expert group in the photography industry), the files of which have the extension .JPG or .JPEG. Allows you to compress an image with a large factor (up to 500 times) due to the irreversible loss of part of the data, which significantly degrades the image quality. The fewer colors an image has, the worse the effect of using the JPEG format, but for color photographs on the screen this is hardly noticeable.
Format GIF(English: Graphics Interchange Format - graphic format for interchange) is the most compacted of the graphic formats, which has no data loss and allows you to reduce the file size several times. Files in this format have the extension .GIF. Low-color images (up to 256 shades), for example, hand-drawn illustrations, are saved and transmitted in this format. The GIF format has interesting features, which allow you to save effects such as background transparency and image animation. The GIF format also allows you to record an image “through the line”, so that, having only part of the file, you can see the entire image, but with a lower resolution.
Graphic format PNG(English: Portable Network Graphic) - a graphic file format similar to the GIF format, but which supports many more colors.
For documents that are transmitted over the Internet, the small file size is very important, since the speed of access to information depends on it. Therefore, when preparing Web pages, types of graphic formats that have a high data compression ratio are used: .JPEG, .GIF, .PNG.
Particularly high demands on image quality are imposed in the printing industry. This industry uses a special format TIFF(eng. Tagged Image File Format - tagged (tagged) image file format). Files in this format have the extension .TIF or .TIFF. They provide compression with a sufficient coefficient and the ability to store additional data in the file, which in the figure is located in auxiliary layers and contains annotations and notes on the figure.
Format PSD(English: PhotoShop Document). Files in this format have the extension .PSD. This is a Photoshop program format that allows you to record a raster image with many layers, additional color channels, masks, i.e. this format can save everything that the user has created visible on the monitor.

Vector Graphics File Formats

There are many fewer vector graphics file formats. Let us give examples of the most common of them.
WMF(English: Windows MetaFile - Windows metafile) - a universal format for Windows add-ons. Used to store a collection of Microsoft Clip Gallery graphics. The main disadvantages are color distortion and the inability to save a number of additional object parameters.
CGM(English: Computer Graphic Metafile - computer graphics metafile) - widely uses the standard format of vector graphic data on the Internet.
CDR(English: CorelDRaw files - CorelDRaw files) - a format used in the vector graphics editor Corel Draw.
A.I.- a format that is supported by the vector editor Adobe Illustrator.

Construction of a 3D image

With the growth of computing power and the availability of memory elements, with the advent of high-quality graphic terminals and output devices, a large group of algorithms and software solutions have been developed that allow the formation of an image on the screen that represents a certain three-dimensional scene. The first such solutions were intended for architectural and mechanical engineering design tasks.

When forming a three-dimensional image (static or dynamic), its construction is considered within a certain coordinate space, which is called stage. The scene involves working in a three-dimensional, three-dimensional world - which is why the direction is called three-dimensional (3-Dimensional, 3D) graphics.

Separate objects composed of geometric volumetric bodies and sections of complex surfaces are placed on the stage (most often, so-called B-splines). To form an image and perform further operations, surfaces are divided into triangles - minimal flat figures - and are subsequently processed precisely as a set of triangles.

At the next stage “ world” coordinates of grid nodes are recalculated using matrix transformations into coordinates species, i.e. depending on the point of view of the scene. View point position is usually called camera position.

Preparation system workspace
Blender 3D graphics (example from the site
http://www.blender.org)

After formation frame(“wire mesh”) is performed painting over- giving the surfaces of objects certain properties. The properties of a surface are primarily determined by its light characteristics: luminosity, reflectance, absorptivity and scattering ability. This set of characteristics allows you to determine the material whose surface is being modeled (metal, plastic, glass, etc.). Transparent and translucent materials have a number of other characteristics.

Typically, during this procedure, you will also cutting off invisible surfaces. There are many methods for performing such cutting, but the most popular method has become
Z-buffer, when an array of numbers is created indicating “depth” - the distance from a point on the screen to the first opaque point. The next surface points will be processed only when their depth is smaller, and then the Z coordinate will decrease. The power of this method directly depends on the maximum possible distance of a scene point from the screen, i.e. on the number of bits per point in the buffer.

Calculation of a realistic image. Performing these operations allows you to create so-called solid models objects, but this image will not be realistic. To form a realistic image, light sources and is executed illumination calculation every point of visible surfaces.

To give objects realism, the surface of objects is “tightened” texture - image(or the procedure that forms it), determining the nuances of appearance. The procedure is called “texture mapping”. During texture application, stretching and smoothing techniques are applied - filtration. For example, anisotropic filtering, mentioned in the description of video cards, does not depend on the direction of texture transformation.

After determining all the parameters, it is necessary to perform the image formation procedure, i.e. calculating the color of dots on the screen. The calculation procedure is called rendering.When performing such a calculation, it is necessary to determine the light falling on each point of the model, taking into account the fact that it can be reflected, that the surface can block other areas from this source, etc.

There are two main methods used to calculate illumination. The first one is the method inverse ray tracing. With this method the trajectory of those rays that ultimately hit the screen pixels is calculated- in reverse. The calculation is carried out separately for each of the color channels, since light of different spectrums behaves differently on different surfaces.

Second method - emissivity method - involves calculating the integral luminosity of all areas falling into the frame and the exchange of light between them.

The resulting image takes into account the specified camera characteristics, i.e. Viewers.

Thus, as a result large quantity Computing makes it possible to create images that are difficult to distinguish from photographs. To reduce the number of calculations, they try to reduce the number of objects and, where possible, replace the calculation with photography; for example, when forming the background of an image.

Solid model and the final result of the model calculation
(example from the site http://www.blender.org)

Animation and virtual reality

The next step in the development of 3D realistic graphics technologies was the possibility of animation - movement and frame-by-frame changes in the scene. Initially, only supercomputers could handle such a volume of calculations, and they were used to create the first three-dimensional animation videos.

Later, hardware specifically designed for computing and imaging was developed - 3D accelerators. This made it possible to perform such formation in a simplified form in real time, which is used in modern computer games. In fact, now even ordinary video cards include such tools and are a kind of mini-computers for a narrow purpose.

When creating games, filming films, developing simulators, in tasks of modeling and designing various objects, the task of forming a realistic image has another significant aspect - modeling not just the movement and changes of objects, but modeling their behavior, corresponding to the physical principles of the surrounding world.

This direction, taking into account the use of all kinds of hardware for transmitting the influences of the outside world and increasing the effect of presence, is called virtual reality.

To implement such realism, special methods are created for calculating parameters and transforming objects - changes in the transparency of water due to its movement, calculation of the behavior and appearance of fire, explosions, collisions of objects, etc. Such calculations are quite complex, and to implement them in modern programs A number of methods have been proposed.

One of them is processing and use shaders - procedures that change illumination(or exact position)at key points according to some algorithm. This processing allows you to create the effects of a “luminous cloud”, “explosion”, increase the realism of complex objects, etc.

Interfaces for working with the “physical” component of image formation have appeared and are being standardized - which makes it possible to increase the speed and accuracy of such calculations, and therefore the realism of the created model of the world.

Three-dimensional graphics is one of the most spectacular and commercially successful areas in the development of information technology; it is often called one of the main incentives for the development of hardware. Three-dimensional graphics tools are actively used in architecture, mechanical engineering, scientific works, when shooting movies, in computer games, in teaching.

Examples of software products

Maya, 3DStudio, Blender

The topic is very attractive to students of any age and arises at all stages of studying a computer science course. The attractiveness for students is explained by the large creative component in practical work, the visual result, as well as the broad applied focus of the topic. Knowledge and skills in this area are required in almost all sectors of human activity.

In basic school, two types of graphics are considered: raster and vector. The issues of distinguishing one species from another are discussed, as a result - the positive aspects and disadvantages. The areas of application of these types of graphics will allow you to enter the names of specific software products that allow you to process this or that type of graphics. Therefore, materials on the topics: raster graphics, color models, vector graphics will be in greater demand in primary schools. In high school, this topic is supplemented by consideration of the features of scientific graphics and the possibilities of three-dimensional graphics. Therefore, the following topics will be relevant: photorealistic images, modeling of the physical world, compression and storage of graphic and streaming data.

Most of the time is spent on practical work preparing and processing graphic images using raster and vector graphics editors. In basic school, this is usually Adobe Photoshop, CorelDraw and/or MacromediaFlach. The difference between the study of certain software packages in basic and high school is manifested to a greater extent not in the content, but in the forms of work. In basic school, this is practical (laboratory) work, as a result of which students master the software product. In high school, the main form of work becomes an individual workshop or project, where the main component is the content of the task at hand, and the software products used to solve it remain only a tool.

The tickets for primary and secondary schools contain questions related to both the theoretical foundations of computer graphics and practical skills in processing graphic images. Such parts of the topic as calculating the information volume of graphic images and features of graphics coding are present in the control measurement materials of the unified state exam.