Computer graphics is a field of computer science that deals with the creation, storage and processing of various images (drawings, drawings, animations) on a computer.
Computer graphics are classified according to the type of presentation of graphic information and the resulting image processing algorithms. Computer graphics are usually divided into vector and raster.
Under raster understand the way of representing an image as a collection of individual dots (pixels) of different colors or shades.
When you enlarge the raster image several times, it becomes clear that the image consists of a finite number of “squares” of a certain color. These squares are called pixels.
In vector graphics, all images are described in the form of mathematical objects - contours, i.e. the image is divided into a number of graphic primitives - points, straight lines, broken lines, arcs, polygons.
Both of these methods of encoding graphic information have their own characteristics and disadvantages.
Raster graphics allows you to create (reproduce) almost any design using more than 16 million shades of colors, regardless of complexity.
Raster representation of an image is natural for most graphic information input/output devices, such as monitors, matrix and inkjet printers, digital cameras, and scanners.
The main problem with raster graphics is the large volume of files containing images: the larger the number of pixels and the smaller their sizes, the better the image looks.
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 (from pixel– the smallest element of the image, a point (like an atom in a molecule)).
Rice. 1.1.
U vector images, on the contrary, the file size does not depend on the real size of the object, which allows, using the minimum amount of information, describe an arbitrarily large object with a file of minimal size.
Descriptions of objects can be easily changed. This also means that various operations with the drawing, such as moving, scaling, rotating, filling, etc., do not degrade its quality.
Rice. 1.2.
The disadvantages of vector graphics include the following:
- The ability to display in vector form is not available for every object: this may require breaking the object into very large number vector lines, which greatly increases the amount of memory occupied by the image and the time it takes to draw it on the screen.
- The vector format does not make it possible to display smooth color transitions or maintain photographic accuracy of the image.
The choice of raster or vector format depends on the goals and objectives of working with the image. Each type of computer graphics was developed to solve specific problems and has its own specific area of application.
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.
Pixels, resolution, image size
The dimensions of raster images are expressed as the number of pixels horizontally and vertically, for example, 600×800. In this case, this means that the width of the image is 600 pixels and the height is 800 pixels. The number of horizontal and vertical dots may vary for different images.
When an image is displayed on the surface of a screen or paper, it occupies a rectangle of a certain size. For optimal placement of an image on the screen, it is necessary to coordinate the number of pixels in the image, the proportions of the image sides with the corresponding parameters of the display device.
The degree of detail of the image, the number of pixels (dots) allocated per unit area is called resolution.
If the image pixels are output one to one by the output device pixels, the size will be determined only by the resolution of the output device. Accordingly, the higher the screen resolution, the more dots are displayed in the same area and the less grainy and better quality your picture will be.
With a large number of dots placed in a small area, the eye does not notice the mosaic pattern. The opposite is also true: low resolution will allow the eye to notice the raster of the image (“steps”).
A high image resolution with a small plane size of the display device will not allow the entire image to be displayed on it, or during output the image will be “adjusted”, for example, for each displayed pixel the colors of the part of the original image falling within it will be averaged. When you need to display a small image large on a high-resolution device, you have to calculate the colors of the intermediate pixels.
It should be clearly distinguished: screen resolution; printer resolution; image resolution.
All these concepts refer to different objects. These types of permissions are in no way related to each other, until you need to find out which physical size will have a picture on the monitor screen, a print on paper or a file on the hard drive.
Screen (screen image) resolution- this is a property of the computer system (depending on the monitor and video card) and operating system(depends on Windows settings). Screen resolution is measured in pixels and determines the size of the image that can fit entirely on the screen. To measure screen resolution, the designation ppi (pixel per inch) is used.
Printer resolution (printed image) is a printer property that expresses the number of individual dots that can be printed on a unit length area (raster). 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. Depending on the type of paper, choose the following raster frequency values: for newsprint - 70-90 dpi, for medium quality paper - 90-100 dpi, for glossy - 133 dpi and higher.
Image resolution (original) is a property of the image itself. The original resolution is used when entering an image into a computer and is measured in dots per inch (dpi), set when creating an image in a graphics editor or using a scanner. Setting the original resolution depends on your image quality and file size requirements. In general, the rule applies: the higher the quality requirements, the higher the resolution of the original should be.
The image resolution value is stored in the image file and is inextricably linked to another property of the image - its physical size.
Physical size Images 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.
Computer graphics(Also computer graphics) - an area of activity in which computers, along with special software, are used as a tool both for creating (synthesis) and editing images, and for digitizing visual information obtained from the real world for the purpose of its further processing and storage.
The first computers did not have separate means for working with graphics, but were already used to obtain and process images. By programming the memory of the first electronic machines, built on the basis of a matrix of lamps, it was possible to obtain patterns.
In 1950, the military computer Whirlwind-I (Russian: Whirlwind), built into the SAGE system of the US air defense, was the first to use a monitor as a means of displaying visual and graphic information.
In 1957, Russell Kirsch created the first scanner for a computer and obtained the first digital image of his little son Vladlen.
In 1961, programmer S. Russell led the project to create the first computer game with graphics. The creation of the game (“Spacewar!”) took about 200 man-hours. The game was created on a PDP-1 machine.
In 1963, American scientist Ivan Sutherland created the Sketchpad software and hardware system, which made it possible to draw points, lines and circles on a tube with a digital pen. Basic actions with primitives were supported: moving, copying, etc. In fact, it was the first vector editor implemented on a computer.
In the mid-1960s. developments in industrial computer graphics applications appeared. Thus, under the leadership of T. Moffett and N. Taylor, Itek developed a digital electronic drawing machine. In 1964, General Motors introduced the DAC-1 computer-aided design system, developed jointly with IBM.
In 1964, Edward Zijek created the first computer animation - the movement of a satellite around the earth.
In 1968, a group led by N. N. Konstantinov created a computer mathematical model of cat movement. The BESM-4 machine, executing a written program for solving differential equations, drew the cartoon “Kitty,” which was a breakthrough for its time. An alphanumeric printer was used for visualization.
In 1968, computer graphics experienced significant progress with the advent of the ability to store images and display them on a computer display, a cathode ray tube.
Main Applications
Scientific graphics- the first computers were used only to solve scientific and industrial problems. To better understand the results obtained, they were processed graphically, graphs, diagrams, and drawings of the calculated structures were created. The first graphics on the machine were obtained in symbolic printing mode. Then special devices appeared - plotters (plotters) for drawing drawings and graphs with an ink pen on paper. Modern scientific computer graphics makes it possible to conduct computational experiments with a visual representation of their results.
Business graphics- a field of computer graphics designed to visually represent various indicators of the performance of institutions. Planned indicators, reporting documentation, statistical reports - these are the objects for which illustrative materials are created using business graphics.
Construction graphics used in the work of design engineers, architects, and inventors of new technology. This type of computer graphics is a mandatory element of CAD (design automation systems). By means of design graphics, you can obtain both flat images (projections, sections) and spatial three-dimensional images.
Illustrative graphics- this is arbitrary drawing and drawing on a computer screen. Illustrative graphics packages are general purpose application software. The simplest software tools for illustrative graphics are called graphic editors.
Art and advertising graphics- became popular largely thanks to television. Using a computer, commercials, cartoons, computer games, video lessons, video presentations. Graphics packages for these purposes require large computer resources in terms of speed and memory. A distinctive feature of these graphics packages is the ability to create realistic images and “moving pictures”. Obtaining drawings of three-dimensional objects, their rotation, approximation, removal, deformation is associated with a large amount of calculations. The transfer of illumination of an object depending on the position of the light source, the location of shadows, and the texture of the surface requires calculations that take into account the laws of optics.
Computer animation is the production of moving images on a display screen. The artist creates on the screen drawings of the initial and final positions of moving objects; all intermediate states are calculated and depicted by the computer, performing calculations based on a mathematical description of this type of movement. The resulting drawings, displayed sequentially on the screen at a certain frequency, create the illusion of movement.
Multimedia is a combination of high-quality images on a computer screen with sound. Multimedia systems are most widespread in the fields of education, advertising, and entertainment.
Scientific work. Computer graphics is also one of the areas scientific activity. Dissertations are defended in the field of computer graphics, and various conferences are held
Two-dimensional(2D - from English. two dimensions- “two dimensions”) computer graphics are classified according to the type of presentation of graphic information, and the image processing algorithms that follow from it. Computer graphics are usually divided into vector and raster.
Vector graphics
- Vector graphics represents an image as a set of geometric primitives. Typically, points, straight lines, circles, rectangles, and also curves of some order are chosen as them. Objects are assigned certain attributes, for example, line thickness, fill color. The drawing is stored as a set of coordinates, vectors and other numbers that characterize a set of primitives.
An image in vector format gives scope for editing: it can be scaled, rotated, and deformed without loss; Also, simulating three-dimensionality in vector graphics is easier than in raster graphics.
This method of presentation is good for diagrams, used for scalable fonts, business graphics, and is very widely used for creating cartoons and simply videos of various contents. - Raster graphics always operates on a two-dimensional array (matrix) of pixels. Each pixel is assigned a value for brightness, color, transparency - or a combination of these values. A raster image has a number of rows and columns.
Any image can be represented in raster form, but this storage method has its drawbacks: a larger amount of memory required for working with images, losses during editing.
Raster graphics
Fractal graphics
Fractal graphics based on usage fractals- objects, individual elements of which inherit the properties of parent structures. 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.
3D graphics(3D - from English. three dimensions- “three dimensions”) operates with objects in three-dimensional space. Usually the results are a flat picture, a projection. Three-dimensional computer graphics are widely used in cinema and computer games.
3D graphics happen polygonal And voxel. Voxel graphics are similar to raster graphics. An object consists of a collection of three-dimensional shapes, most often cubes. And in polygonal computer graphics, all objects are usually represented as a set of surfaces, the minimal surface is called a polygon. Triangles are usually chosen as polygons.
CGI(English) computer-generated imagery, lit. "computer-generated images") are still and moving images generated using three-dimensional computer graphics and used in the visual arts, printing, cinematic special effects, television and simulation.
The creation of moving images is done by computer animation, which is a narrower area of CGI graphics, applicable, including 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.
Working with computer graphics is one of the most popular areas of use personal computer, and not only professional artists and designers are involved in this work. At any enterprise, from time to time there is a need to submit advertisements to newspapers and magazines or simply issue an advertising leaflet or booklet. Large companies order such work from special design bureaus or advertising agencies. Small businesses with limited budgets often make do with their own resources and available software.
Not a single modern multimedia program can do without computer graphics. Working on graphics takes up to 90% of the working time of programming teams producing programs for mass use.
The main labor costs in the work of editorial offices and publishing houses also consist of artistic and design work with graphic programs.
Types of computer graphics
Despite the fact that there are many classes of software for working with computer graphics, there are only three types of computer graphics. These are raster graphics, vector graphics 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. More often, illustrations prepared by the artist on paper or photographs are used for this purpose. Accordingly, most graphic editors designed for working with raster illustrations are focused not so much on the creation of images, but rather on their processing. For now, only raster illustrations are used on the Internet.
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.
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.
Seraphim Vagitov (Sevastopol)
Performing various works with graphics is one of the most popular uses of a personal computer, and, contrary to popular belief, this activity is not only for professional artists and designers. Any small business from time to time needs, for example, the design of advertisements for newspapers and magazines or the production of a regular advertising booklet.
Almost no modern multimedia program today can do without computer graphics. Work on graphic components takes up the lion's share (about 90%) of the working time of programmers involved in the development of consumer programs.
There is a large amount of software for working with computer graphics, however, despite this, there are only 3 types of this graphics. They differ according to the principles of image formation when reflected on monitor screens or when printed on paper. Let's look at them in more detail.
Raster graphics used in the creation of multimedia and printing publications. Images made using raster graphics are rarely created manually using computer programs. Most often, scanned images previously prepared on paper or ordinary photographs are used for these purposes. Recently, inputting raster images into a computer using digital photo and video cameras has been widely practiced.
Therefore, almost all graphic editors designed to work with raster images are focused primarily on processing them, rather than creating them. Today, only raster images are used on the Internet.
On the contrary, programs for working with vector graphics are intended primarily for creating images and to some extent for processing. Such programs are widely used in various advertising agencies, design studios and popular publications. The fact is that tasks associated with design based on the use of fonts and simple geometric shapes, it is easier to solve using vector graphics. On the Internet you can find excellent examples of works of art created using vector graphics processing programs, but in this sense they are the exception rather than the rule. This is due to the fact that the artistic processing of illustrations with such programs is quite complex.
Software tools for development are also of interest. fractal graphics. They automatically generate images using mathematical calculations. The essence of creating a fractal composition is not in design or drawing, but in programming. Fractal graphics are rarely used to design printed or electronic documents, but are often used in various types of entertainment programs.
Raster graphics
To understand what a raster image is, you need to understand its structure. The main component of any raster image is a dot. If an image is intended to be viewed on a screen, then such a point is called a pixel. These images can have different sizes, for example, 640x480, 800x600, 1024x768 or more pixels.
The size of an image is directly related to its resolution. This parameter is measured in the number of dots per inch of image area (dpi). For example, a 15-inch monitor displays an image measuring approximately 28x21cm. Knowing that one inch is 25.4 mm, we can calculate that when working in 800x600 pixel mode, the image resolution on the screen will be 72 dpi.
Printing images requires much higher resolution. For full-color printing, images with a resolution of 200-300 dpi are used. An ordinary photograph of 10x15 cm has about 1000x1500 pixels. This means that such an image consists of 1.5 million pixels, and if it is color and three bytes are used to coordinate each pixel, then the file size corresponding to a regular photograph will be about 4 MB.
As you can see, the main problem with all raster images is their large volume. The second disadvantage associated with raster images is the inability to see small details. Since the image consists of dots, increasing its size inevitably entails distortion of the illustration and makes it blurry. This effect is known as pixelation.
Vector graphics
The main element of a vector image is a line. Raster graphics also contain lines, but there they are present as a combination of dots. Accordingly, the longer the raster line, the more memory the image takes up. If we talk about a vector image, then the amount of memory occupied by a line does not depend on the size of this line, since the line in this case is presented in the form of a formula, or rather, in the form of certain parameters. And therefore, no matter what we do in relation to this line, only its parameters change, which are sequentially stored in memory cells.
A line is an elementary object in vector graphics. All vector illustrations consist of lines. Simpler objects can be combined into more complex ones by increasing the number of lines. For example, a quadrilateral can be represented as four interconnected lines, and a cube can be represented as twelve, or six quadrangles. Due to this approach, vector graphics are often called object-oriented graphics.
Like other objects, lines have certain properties. These include: line shape, thickness, color, and character (solid line, dotted line, etc.). Lines that close have the property of filling. The inner part of the contour closed in this way can be filled with color, texture or a pre-prepared raster image.
Unlike raster graphics with their significant volumes and the impossibility of scaling without loss of quality, vector graphics are free of these disadvantages, but their use significantly complicates the creation of artistic illustrations. Most often, vector graphics tools are used to perform tasks related to design, drawings and design work.
In vector graphics, fairly complex compositions take up a small amount of space. Scaling issues are also easily resolved. If necessary, images can be enlarged to the smallest detail.
Fractal graphics
Fractal graphics, like vector graphics, are the result of calculations, but their main difference is that no objects are stored in the computer's memory. The image is constructed according to an equation (or system of equations), so only the formula is saved. If you change the coefficients in the equation, you get a completely different picture.
The simplest fractal object is a fractal triangle. In order to get a fractal triangle, you need to construct a regular equilateral triangle. Then divide each side into 3 segments. Exactly in the middle of this side, build another similar triangle with a side 2/3 smaller than the side of the first triangle. Repeat the same operations with the triangles obtained as a result of such manipulations. Successive generations of triangles imitate the properties of their parent structures. This is how a fractal figure is formed. This process can be continued indefinitely.
Many living and inanimate objects of nature are endowed with fractal properties. You may find that an ordinary snowflake, when magnified, turns out to be a fractal object. The growth of crystals and plants owes its existence to the fractal algorithms that underlie it.
The capabilities of fractal graphics in creating various images of living nature through calculations are often used to generate unusual, fantastic illustrations.
Color model concept
Colors in nature are rarely simple. Most color shades are created by mixing primary colors. The method of dividing a color shade into its component components is called a 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 by the names: CMYK, RGB and HSB.
The most common example is the CMYK color model. It is used to identify colors in conventional color printing. A huge range of colors is obtained by mixing 4 primary colors: blue, red, yellow and black. The English names of these colors make up the abbreviation CMYK. The last color, Black, is designated by the letter K to avoid confusion, since the name blue(Blue) starts with the same letter.
The CMYK model was the basis for the standard Corel DRAW color palette. This palette is called Corel DRAW.сpl. (cpl extension is assigned to the names of all Corel DRAW palettes). It consists of approximately 100 colors, all of which have their own names, such as Navy Blue, Deep Purple, Dusty Rose, etc.
Palette Corel DRAW.сpl. received general recognition due to the following circumstances:
- Since this is a standard palette, work with the program begins with it. In fact, many users don’t even switch to other palettes.
- You can customize this palette yourself, add and remove colors, and edit existing ones.
CMYK color model
This model is used for preparing printed images exclusively.
The peculiarity of printing in a printing house is that the image is printed in several stages. Cyan, magenta, yellow and black are alternately applied to the paper to create a full-color illustration. To do this, the image obtained on the computer is divided into 4 single-color images before printing. This process is called color separation. Many modern graphic editors have an arsenal of tools to carry out this operation.
RGB color model
The easiest model to understand. Computer monitors and TVs operate in RGB mode. The bottom line is that every color consists of 3 main components: red, green and blue. Hence the abbreviation RGB. These colors are called primary. The RGB model is used when it is necessary to prepare an image for display on the screen.
Graphic editors are equipped with tools for converting an image from one color model to another. But still, the RGB model is the most “native” for a computer.
HSB color model
In the HSB color model, when creating full colors, the components of those colors are hue (H), saturation (S), and brightness (B). This model most closely matches human perception of colors.
The color wheel can contain up to 360 shades. The position of a color on the radius of the color wheel determines its saturation. The further the color is from the center, the richer the shade. When printed, this model will be automatically converted by the program to a CMYK model.
Basic concepts of computer graphics.
Basic concepts on the topic
General characteristics and functionality of the Photoshop graphic editor
General characteristics and functionality of the Corel DRAW graphic editor
Graphic data formats
Computer graphics, its classification, basic concepts
Topic 5 Technologies and systems for processing graphic information
Digital commonly referred to as an image created from scratch using a computer program; or an image (slide, photograph) converted into electronic information in order to view, edit and manage it on a computer screen.
Devices that convert graphic images into digital form are called digitizing(scanners, digital cameras)
A color model is a means of describing colors for the purpose of their further consistent reconstruction.
There are three types of computer graphics: raster graphics, vector graphics And fractal graphics. They differ in the principles of image formation when displayed on a monitor screen or when printed on paper.
Raster graphics 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. Accordingly, most graphic editors designed for working with raster illustrations are focused not so much on creating images, but on processing them.
vector graphics 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.
Software tools for working with fractal graphics are designed for automatic generation of images using mathematical calculations. Creating a fractal artistic composition is not about drawing or design, but about programming. Fractal graphics are often used in entertainment programs.
Image resolution and size. In computer graphics, one should 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 image on the monitor screen, print on paper or file on the hard drive will have.
Screen resolution- this 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 and determines the size of the image that can fit entirely on the screen.
Printer resolution is a printer property that expresses the number of individual dots that can be printed on a unit length area. 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 and is set when creating an image in a graphics editor or using a scanner. The image resolution value is stored in the image file and is inextricably linked to another property of the image - its physical size.
Physical size Images 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, its width and height are specified in pixels in order to know how much of the screen it occupies.
Vector graphics. Unlike raster graphics, in which the basic element of the image is a point, in vector graphics the basic element is a line (it does not matter whether it is a straight line or a curve). Of course, there are also lines in raster graphics, but... [read more]
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