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Ken Presents...

Graphics Jargon...

ActionScript
The scripting language used in Macromedia Flash. It is similar in syntax to JavaScript.

Aliasing
(1) In computer graphics, the process by which smooth curves and other lines become jagged because the resolution of the graphics device or file is not high enough to represent a smooth curve. Smoothing and antialiasing techniques can reduce the effect of aliasing.

(2) In digital sound, aliasing is a static distortion resulting from a low sampling rate-below 40 kilohertz (Khz).

Alpha Channel
In graphics, a portion of each pixel's data that is reserved for transparency information. 32-bit graphics systems contain four channels -- three 8-bit channels for red, green, and blue (RGB) and one 8-bit alpha channel. The alpha channel is really a mask -- it specifies how the pixel's colors should be merged with another pixel when the two are overlaid, one on top of the other.

Typically, you wouldn't define the alpha channel on a pixel-by-pixel basis, but rather per object. Different parts of the object would have different levels of transparency depending on how much you wanted the background to show through. This allows you to create rectangular objects that appear as if they are irregular in shape -- you define the rectangular edges as transparent so that the background shows through. This is especially important for animation, where the background changes from one frame to the next.

Rendering overlapping objects that include an alpha value is called alpha blending.

Anchor
In desktop publishing, to fix a graphical object so that its position relative to some other object remains the same during repagination. Frequently, for example, you may want to anchor a picture next to a piece of text so that they always appear together.

Animated GIF
A type of GIF image that can be animated by combining several images into a single GIF file. Applications that support the animated GIF standard, GIF89A, cycle through each image. GIF animation doesn't give the same level of control and flexibility as other animation formats but it has become extremely popular because it is supported by nearly all Web browsers. In addition, animated GIF files tend to be quite a bit smaller that other animation files, such as Java applets.

Animation
A simulation of movement created by displaying a series of pictures, or frames. Cartoons on television is one example of animation. Animation on computers is one of the chief ingredients of multimedia presentations. There are many software applications that enable you to create animations that you can display on a computer monitor.

Note the difference between animation and video. Whereas video takes continuous motion and breaks it up into discrete frames, animation starts with independent pictures and puts them together to form the illusion of continuous motion.

Antialiasing
In computer graphics, antialiasing is a software technique for diminishing jaggies - stairstep-like lines that should be smooth. Jaggies occur because the output device, the monitor or printer, doesn't have a high enough resolution to represent a smooth line. Antialiasing reduces the prominence of jaggies by surrounding the stairsteps with intermediate shades of gray (for gray-scaling devices) or color (for color devices). Although this reduces the jagged appearance of the lines, it also makes them fuzzier.

Another method for reducing jaggies is called smoothing, in which the printer changes the size and horizontal alignment of dots to make curves smoother.

Antialiasing is sometimes called oversampling.

Autotracing
The process of converting a bit-mapped image (or raster image) into a vector image. In a bit-mapped image, each object is represented by a pattern of dots, while in a vector image every object is defined geometrically.

Most autotracing packages read files in a variety of bit-mapped formats (PCX and TIFF are the most common) and produce a file in a vector format such as Encapsulated PostScript (EPS ). The conversion techniques used, and the accuracy of the conversion process, differ from one package to another.

Autotracing is particularly useful for manipulating images produced by an optical scanner. Scanners produce bit-mapped images that cannot be manipulated by sophisticated tools until they have been converted into a vector format through autotracing.

Bézier curve
Pronounced bez-ee-ay, curved lines (splines) defined by mathematical formulas. Nearly all draw programs support Bézier curves.

Named after the French mathematician Pierre Bézier, Bézier curves employ at least three points to define a curve. The two endpoints of the curve are called anchor points. The other points, which define the shape of the curve, are called handles, tangent points, or nodes. Attached to each handle are two control points. By moving the handles themselves, or the control points, you can modify the shape of the curve.

Bit Block Transfer
A transformation of a rectangular block of pixels. Typical transformations include changing the color or shade of all pixels or rotating the entire rectangle. Many modern video adapters include hardwired bit block transformations, which execute much faster than they do when executed by software routines.

Bit Map
A representation, consisting of rows and columns of dots, of a graphics image in computer memory. The value of each dot (whether it is filled in or not) is stored in one or more bits of data. For simple monochrome images, one bit is sufficient to represent each dot, but for colors and shades of gray, each dot requires more than one bit of data. The more bits used to represent a dot, the more colors and shades of gray that can be represented.

The density of the dots, known as the resolution, determines how sharply the image is represented. This is often expressed in dots per inch (dpi ) or simply by the number of rows and columns, such as 640 by 480.

To display a bit-mapped image on a monitor or to print it on a printer, the computer translates the bit map into pixels (for display screens) or ink dots (for printers). Optical scanners and fax machines work by transforming text or pictures on paper into bit maps.

Bit-mapped graphics are often referred to as raster graphics. The other method for representing images is known as vector graphics or object-oriented graphics. With vector graphics, images are represented as mathematical formulas that define all the shapes in the image. Vector graphics are more flexible than bit-mapped graphics because they look the same even when you scale them to different sizes. In contrast, bit-mapped graphics become ragged when you shrink or enlarge them.

Fonts represented with vector graphics are called scalable fonts , outline fonts , or vector fonts. The best-known example of a vector font system is PostScript. Bit-mapped fonts, also called raster fonts, must be designed for a specific device and a specific size and resolution.

Bitblt
Pronounced bit-blit, see under bit block transfer.

Bit-Mapped Graphics
Refers to hardware and software that represent graphics images as bit maps. The other method for representing images is known as vector graphics.

Block Graphics
Graphical images created in character mode.

Bump Mapping
Bump mapping is used to add detail to an image without increasing the number of polygons. Bump mapping relies on light-reflection calculations to create small bumps on the surface of the object in order to give it texture; the surface of the object is not changed.

Bumps are applied by matching up a series of grayscale pixels with colored pixels on the rendered, colored object. Lighter grayscale pixels create a sense of maximum relief or maximum indentation; darker pixels have less effect.

A computer must contain a supporting 3D graphics card when it runs an application that has been coded to include bump maps. If the graphics card does not support bump mapping, then the bumps won't be seen. In the case of computer games, the programmer usually will code an alternate version that doesn't use bump maps. This version will look flatter and less real.

Capture
To save a particular state of a program. The term capture often refers to saving the information currently displayed on a display screen. You can capture the screen to a printer or to a file. The act of saving a display screen is called a screen capture. Video capture refers to storing video images in a computer.

The term capture is also used to describe the recording of keystrokes during the definition of a macro.

Character Mode
Many video adapters support several different modes of resolution. All such modes are divided into two general categories: character mode (also called text mode) and graphics mode. In character mode, the display screen is treated as an array of blocks, each of which can hold one ASCII character. In graphics mode, the display screen is treated as an array of pixels, with characters and other shapes formed by turning on combinations of pixels.

Of the two modes, character mode is much simpler. Programs that run in character mode generally run much faster than those that run in graphics mode, but they are limited in the variety of fonts and shapes they can display. Programs that run entirely in character mode are called character-based programs.

Clip
In computer graphics, to cut off a portion of a graphic at a defined boundary. Most bit-mapped graphics utilities provide a clip feature than enables you to draw a window around an object and clip everything outside of the window.

Clip Art
Electronic illustrations that can be inserted into a document. Many clip-art packages are available, some general and others specialized for a particular field. Most clip-art packages provide the illustrations in several file formats so that you can insert them into various word-processing systems.

Color Depth
The number of distinct colors that can be represented by a piece of hardware or software. Color depth is sometimes referred to as bit depth because it is directly related to the number of bits used for each pixel. A 24-bit video adapter, for example, has a color depth of 2 to the 24th power (about 16.7 million) colors. One would say that its color depth is 24 bits.

Computer Imaging
A field of computer science covering digital images - images that can be stored on a computer, particularly bit-mapped images. Computer imaging is a wide field that includes digital photography, scanning, and composition and manipulation of bit-mapped graphics.

Computer imaging is often called digital imaging.

Continuous Tone
Refers to images that have a virtually unlimited range of color or shades of grays. Photographs and television images, for example, are continuous-tone images. In contrast, computer hardware and software is digital, which means that they can represent only a limited number of colors and gray levels. Converting a black-and-white continuous-tone image into a computer image is known as gray scaling.

Continuous-tone printers can print each dot at many different shades of lightness and darkness. Though this isn't true continuous-tone because the level of shades is limited, there are enough shades (256 or more) so that the difference between one shade and the next is imperceptible to the human eye.

Crop
In computer graphics, to cut off the sides of an image to make it the proper size or to remove unwanted parts. Most graphics applications allow you to crop images with a clip feature.

Digital Photography
The art and science of producing and manipulating digital photographs -- photographs that are represented as bit maps.

Once a photograph is in digital format, you can apply a wide variety of special effects to it with image enhancing software. You can then print the photo out on a normal printer or send it to a developing studio which will print it out on photographic paper.

Although the resolution of digital photos is not nearly as high as photos produced from film, digital photography is ideal when you need instant, low-resolution pictures. It's especially useful for photos that will be displayed on the World Wide Web because Web graphics need to be low resolution anyway so that they can be downloaded quickly.

Dithering
Creating the illusion of new colors and shades by varying the pattern of dots. Newspaper photographs, for example, are dithered. If you look closely, you can see that different shades of gray are produced by varying the patterns of black and white dots. There are no gray dots at all. The more dither patterns that a device or program supports, the more shades of gray it can represent. In printing, dithering is usually called halftoning, and shades of gray are called halftones.

Note that dithering differs from gray scaling. In gray scaling, each individual dot can have a different shade of gray.

EXIF
Short for Exchangeable Image File, a format that is a standard for storing interchange information in digital photography image files using JPEG compression. Almost all new digital cameras use the EXIF annotation, storing information on the image such as shutter speed, exposure compensation, F number, what metering system was used, if a flash was used, ISO number, date and time the image was taken, whitebalance, auxiliary lenses that were used and resolution.

EXIF files use the JPEG DCT format, so the image data can be read by any application supporting JPEG, including essentially all Web browsers and image editing, desktop presentation and document creation applications.

Feathering
In desktop publishing, feathering is the process of softening the edges of an image in the foreground so that it blends into the background image with less contrast.

FIF
(Fractal Image Format) A graphics file format from Iterated Systems, Inc. (www.iterated.com) that uses fractal geometry to compress images. (Fractals are structures possessing similar-looking forms of many different sizes. They can be used to create any real-world object, like a mountain or a cloud, provided it doesn't correspond to a simple geometric shape.) These fractals can be expressed in mathematical terms, allowing an entire image to be recorded as repeated patterns. This can reduce the file size to 1/100th of a pixellated version.

Fill
(1) In graphics applications, to paint the inside of an enclosed object. Typically, you can choose a color and pattern, and then paint the object with a fill tool. The area that is painted is called the fill area.

(2) In spreadsheet applications, to copy the contents of one cell to an entire range of cells -- that is, to fill the range with a formula or value.

Flash
A bandwidth friendly and browser independent vector-graphic animation technology. As long as different browsers are equipped with the necessary plug-ins, Flash animations will look the same.

With Flash, users can draw their own animations or import other vector-based images.

Flash was known as FutureSplash until 1997, when Macromedia Inc. bought the company that developed it.

Foreground
(1) In multiprocessing systems, the process that is currently accepting input from the keyboard or other input device is sometimes called the foreground process.

(2) On display screens, the foreground consists of the characters and pictures that appear on the screen. The background is the uniform canvas behind the characters and pictures.

Fractal
A word coined by Benoit Mandelbrot in 1975 to describe shapes that are "self-similar" -- that is, shapes that look the same at different magnifications. To create a fractal, you start with a simple shape and duplicate it successively according to a set of fixed rules. Oddly enough, such a simple formula for creating shapes can produce very complex structures, some of which have a striking resemblance to objects that appear in the real world. For example, graphics designers use fractals to generate images of mountainous landscapes, coastlines, and flowers. In fact, many of the computer -generated images that appear in science fiction films utilize fractals.

GPU
Used primarily for 3-D applications, a graphics processing unit is a single-chip processor that creates lighting effects and transforms objects every time a 3D scene is redrawn. These are mathematically-intensive tasks, which otherwise, would put quite a strain on the CPU. Lifting this burden from the CPU frees up cycles that can be used for other jobs.

The first company to develop the GPU is NVIDIA Inc. Its GeForce 256 GPU is capable of billions of calculations per second, can process a minimum of 10 million polygons per second, and has over 22 million transistors, compared to the 9 million found on the Pentium III. Its workstation version called the Quadro, designed for CAD applications, can process over 200 billion operations a second and deliver up to 17 million triangles per second.

The GeForce NVIDIA GPU card is compatible with the following graphics APIs : OpenGL and Microsoft's DirectX, Intel's Accelerated Graphics Port (AGP) technology and AMD 's 3DNow!

The Quadro is an OpenGL specific card with driver support for Pentium III Xeon and AMD Athlon CPUs.

Graphics
Pertains to any computer device or program that makes a computer capable of displaying and manipulating pictures. For example, laser printers and plotters are graphics devices because they permit the computer to output pictures. A graphics monitor is a display monitor that can display pictures. A graphics board (or graphics card) is a printed circuit board that, when installed in a computer, permits the computer to display pictures.

Many software applications include graphics components. Such programs are said to support graphics. For example, certain word processors support graphics because they let you draw or import pictures. All CAD/CAM systems support graphics. Some database management systems and spreadsheet programs support graphics because they let you display data in the form of graphs and charts. Such applications are often referred to as business graphics.

Graphics Based
Refers to software and hardware that treat objects on a display screen as bit maps or geometrical shapes rather than as characters. In contrast, character-based systems treat everything as ASCII or extended ASCII characters.

All graphics software is by definition graphics based. Systems that manipulate text can also be graphics based; for example, desktop publishing systems are essentially graphics-based word processors.

Traditionally, most DOS applications -- word processors, spreadsheets, and database management systems -- have been character based. Windows and the Mac OS are graphics-based.

Gray Scaling
The use of many shades of gray to represent an image. Continuous-tone images, such as black-and-white photographs, use an almost unlimited number of shades of gray. Conventional computer hardware and software, however, can only represent a limited number of shades of gray (typically 16 or 256). Gray-scaling is the process of converting a continuous-tone image to an image that a computer can manipulate.

While gray scaling is an improvement over monochrome, it requires larger amounts of memory because each dot is represented by from 4 to 8 bits. At a resolution of 300 dpi, you would need more than 8 megabytes to represent a single 8½ by 11-inch page using 256 shades of gray. This can be reduced considerably through data compression techniques, but gray scaling still requires a great deal of memory.

Many optical scanners are capable of gray scaling, using from 16 to 256 different shades of gray. However, gray scaling is only useful if you have an output device -- monitor or printer -- that is capable of displaying all the shades. Most color monitors are capable of gray scaling, but the images are generally not as good as on dedicated gray-scaling monitors.

Note that gray scaling is different from dithering. Dithering simulates shades of gray by altering the density and pattern of black and white dots. In gray scaling, each individual dot can have a different shade of gray.

Halftone
In printing, a continuous tone image, such as a photograph, that has been converted into a black-and-white image. Halftones are created through a process called dithering, in which the density and pattern of black and white dots are varied to simulate different shades of gray.

In conventional printing, halftones are created by photographing an image through a screen. The screen frequency, measured in lines per inch, determines how many dots are used to make each spot of gray. In theory, the higher the screen frequency (the more lines per inch), the more accurate the halftone will be. However, actual screen frequencies are limited by the technology because higher screen frequencies create smaller, more tightly packed dots. If you are printing on a low resolution device, therefore, you may get better results with a lower screen frequency.

Modern desktop publishing systems can create halftones by simulating the conventional photographic process. This is why some programs allow you to specify a screen frequency even when no actual screen is used.

Handle
(1) In many applications, when you select a graphical object, an outline of the object appears with small boxes. Each box is a handle. By dragging the handles, you can change the shape and size of the object.

(2) In programming, a handle is a token, typically a pointer, that enables the program to access a resource, such as a library function.

(3) When communicating via an online service, your handle is the name that you use to identify yourself. It could be your real name, a nickname, or a completely fictitious name.

Image Map
A single graphic image containing more than one hot spot. For example, imagine a graphic of a bowl of fruit. When you click on a banana, the system displays the number of calories in a banana and when you click on an apple, it displays the number of calories in an apple.

Image maps are used extensively on the World Wide Web. Each hot spot in a Web image map takes you to a different Web page.

Jaggies
Stairlike lines that appear where there should be smooth straight lines or curves. Jaggies can occur for a variety of reasons, the most common being that the output device (display monitor or printer) does not have enough resolution to portray a smooth line. In addition, jaggies often occur when a bit-mapped image is converted to a different resolution. This is one of the advantages vector graphics has over bit-mapped graphics -- the output looks the same regardless of the resolution of the output device.

The effect of jaggies can be reduced somewhat by a graphics technique known as antialiasing. Antialiasing smoothes out jagged lines by surrounding the jaggies with shaded pixels. In addition, some printers can reduce jaggies with a technique known as smoothing.

Line Art
A type of graphic consisting entirely of lines, without any shading. Most art produced on computers is not line art because the computer makes it so easy to add subtle shadings.

Mask
A filter that selectively includes or excludes certain values. For example, when defining a database field, it is possible to assign a mask that indicates what sort of value the field should hold. Values that do not conform to the mask cannot be entered.

MCGA
Abbreviation of multicolor/graphics array (or memory controller gate array), the graphics system built into some older PCs. It provides graphics capabilities equal to or greater than MDA and CGA, but it is not as powerful as VGA. Like VGA, MCGA uses analog signals.

Megapixel
One million pixels. The term is used in reference to the resolution of a graphics device, such as a scanner, digital camera or monitor.

moiré
An undesirable pattern that appears when a graphic image is displayed or printed with an inappropriate resolution. Moiré patterns are difficult to predict because they result from a complex combination of parameters: the size of the image, resolution of the image, resolution of the output device, halftone screen angle, etc.

If you're planning to print a graphic image (particularly a bit-mapped image) on a high-resolution printer, it's a good idea to print a test page first to see if there are any moiré patterns. If there are, you can sometimes eliminate them by changing the resolution of the printout, resizing the image, or changing the angle of the halftone screen.

Monochrome
One color. Monitors, for example, can be monochrome, grayscale or color. Monochrome monitors actually use two colors, one for the display image (the foreground) and one for the background. Graphic images can also be monochrome, grayscale, or color.

Morphing
Short for metamorphosing, morphing refers to an animation technique in which one image is gradually turned into another. Many advanced animation programs support some type of morphing feature.

Object-oriented Graphics
The representation of graphical objects, such as lines, arcs, circles, and rectangles, with mathematical formulas. This method of describing objects enables the system to manipulate the objects more freely. In an object-oriented system, for example, you can overlap objects but still access them individually, which is difficult in a bit-mapped system. Also, object-oriented images profit from high-quality output devices. The higher the resolution of a monitor or printer, the sharper an object-oriented image will look. In contrast, bit-mapped images always appear the same regardless of a device's resolution.

One of the most widely used formats for object-oriented graphics is PostScript. PostScript is a page description language (PDL) that makes it possible to describe objects and manipulate them in various ways. For example, you can make objects smaller or larger, turn them at various angles, and change their shading and color. A font described in PostScript, therefore, can easily be transformed into another font by changing its size or weight. Object-oriented fonts are called outline fonts, scalable fonts, or vector fonts.

Object-oriented graphics is also called vector graphics, whereas bit-mapped graphics is sometimes called raster graphics.

Palette
(1) In computer graphics, a palette is the set of available colors. For a given application, the palette may be only a subset of all the colors that can be physically displayed. For example, a SVGA system can display 16 million unique colors, but a given program would use only 256 of them at a time if the display is in 256-color mode. The computer system's palette, therefore, would consist of the 16 million colors, but the program's palette would contain only the 256-color subset.

A palette is also called a CLUT (color look-up table).

On monochrome systems, the term palette is sometimes used to refer to the available fill patterns.

(2) In paint and illustration programs, a palette is a collection of symbols that represent drawing tools. For example, a simple palette might contain a paintbrush, a pencil, and an eraser.

Pixel
Short for Picture Element, a pixel is a single point in a graphic image. Graphics monitors display pictures by dividing the display screen into thousands (or millions) of pixels, arranged in rows and columns. The pixels are so close together that they appear connected.

The number of bits used to represent each pixel determines how many colors or shades of gray can be displayed. For example, in 8-bit color mode, the color monitor uses 8 bits for each pixel, making it possible to display 2 to the 8th power (256) different colors or shades of gray.

On color monitors, each pixel is actually composed of three dots -- a red, a blue, and a green one. Ideally, the three dots should all converge at the same point, but all monitors have some convergence error that can make color pixels appear fuzzy.

The quality of a display system largely depends on its resolution, how many pixels it can display, and how many bits are used to represent each pixel. VGA systems display 640 by 480, or about 300,000 pixels. In contrast, SVGA systems display 800 by 600, or 480,000 pixels. True Color systems use 24 bits per pixel, allowing them to display more than 16 million different colors.

Plot
To produce an image by drawing lines. You can program a computer to plot images on a display screen or on paper.

Polyline
In computer graphics, a continuous line composed of one or more line segments. You can create a polyline by specifying the endpoints of each segment. In draw programs, you can treat a polyline as a single object, or divide it into its component segments.

Primitive
A low-level object or operation from which higher-level, more complex objects and operations can be constructed. In graphics, primitives are basic elements, such as lines, curves, and polygons, which you can combine to create more complex graphical images. In programming, primitives are the basic operations supported by the programming language. A programmer combines these primitives to create more complex operations, which are packaged as functions, procedures, and methods.

Resolution
Refers to the sharpness and clarity of an image. The term is most often used to describe monitors, printers, and bit-mapped graphic images. In the case of dot-matrix and laser printers, the resolution indicates the number of dots per inch. For example, a 300-dpi (dots per inch) printer is one that is capable of printing 300 distinct dots in a line 1 inch long. This means it can print 90,000 dots per square inch.

For graphics monitors, the screen resolution signifies the number of dots (pixels) on the entire screen. For example, a 640-by-480 pixel screen is capable of displaying 640 distinct dots on each of 480 lines, or about 300,000 pixels. This translates into different dpi measurements depending on the size of the screen. For example, a 15-inch VGA monitor (640x480) displays about 50 dots per inch.

Printers, monitors, scanners, and other I/O devices are often classified as high resolution, medium resolution, or low resolution. The actual resolution ranges for each of these grades is constantly shifting as the technology improves.

RLE
The file extension for graphics that have been reduced using run-length encoding. RLE is a compression method that converts consecutive identical characters into a code consisting of the character and the number marking the length of the run. The longer the run, the greater the compression. It works best with black-and-white or cartoon-style graphics, and is used to compress Windows start-up logos.

Scale
To change the size of an object while maintaining its shape. Most graphics software, particularly vector -based packages, allow you to scale objects freely.

Screen Capture
Refers to the act of copying what is currently displayed on a screen to a file or printer. If the system is in graphics mode, the screen capture will result in a graphics file containing a bit map of the image. If the system is in text mode, the screen capture will normally load a file with ASCII codes.

Spline
In computer graphics, a smooth curve that passes through two or more points. Splines are generated with mathematical formulas. Two of the most common types of splines are Bezier curves and b-spline curves.

Sprite
A graphic image that can move within a larger graphic. Animation software that supports sprites enables the designer to develop independent animated images that can then be combined in a larger animation. Typically, each sprite has a set of rules that define how it moves and how it behaves if it bumps into another sprite or a static object.

SVG
Scalable Vector Graphics is a vector graphics language written in XML. Using SVG, graphics can be coded directly into an XML document.

SVG works by assigning attributes to SVG elements. For instance, the "svg" element takes on the attributes x, y, height, width, allowZoomAndPan. This element is the outermost container, which defines the image. The allowZoomAndPan attribute gives the author control over zooming in and panning over the image. Other elements define shapes and lines, others define opacity and others define ways to embed JPEGs and PNG s into the SVG image. Still, these are only a few SVG elements; there are many more.

Currently, SVG images cannot be seen through a Web browser ; therefore, a user must download a SVG viewer.

Texel
Short for Texture Element. Like a pixel, a texel is the base unit of a graphic, although texels make up textured graphics - graphics that define the surface of three dimensional objects. The base unit of the surface of a 3D brick wall would be a texel, while a two-dimensional wall would consist of pixels.

Text Mode
A video mode in which a display screen is divided into rows and columns of boxes. Each box can contain one character. Text mode is also called character mode.

All video standards for the PC, including VGA, support a text mode that divides the screen into 25 rows and 80 columns. In addition to text mode, most video adapters support a graphics mode, in which the display screen is divided into an array of pixels.

Whereas character-based programs run in text mode, all graphics-based programs run in graphics mode.

Vector Graphics
Same as object-oriented graphics, refers to software and hardware that use geometrical formulas to represent images. The other method for representing graphical images is through bit maps, in which the image is composed of a pattern of dots. This is sometimes called raster graphics. Programs that enable you to create and manipulate vector graphics are called draw programs, whereas programs that manipulated bit-mapped images are called paint programs.

Vector-oriented images are more flexible than bit maps because they can be resized and stretched. In addition, images stored as vectors look better on devices (monitors and printers) with higher resolution, whereas bit-mapped images always appear the same regardless of a device's resolution. Another advantage of vector graphics is that representations of images often require less memory than bit-mapped images do.

Almost all sophisticated graphics systems, including CADD systems and animation software, use vector graphics. In addition, many printers (PostScript printers, for example) use vector graphics. Fonts represented as vectors are called vector fonts, scalable fonts, object-oriented fonts, and outline fonts.

Note that most output devices, including dot-matrix printers, laser printers, and display monitors, are raster devices (plotters are the notable exception). This means that all objects, even vector objects, must be translated into bit maps before being output. The difference between vector graphics and raster graphics, therefore, is that vector graphics are not translated into bit maps until the last possible moment, after all sizes and resolutions have been specified. PostScript printers, for example, have a raster image processor (RIP) that performs the translation within the printer. In their vector form, therefore, graphics representations can potentially be output on any device, with any resolution, and at any size.

Video Mode
The setting of a video adapter. Most video adapters can run in either text mode or graphics mode. In text mode, a monitor can display only ASCII characters. In graphics mode, a monitor can display any bit-mapped image. In addition to the text and graphics modes, video adapters offer different modes of resolution and color depth.

Z-buffer
An area in graphics memory reserved for storing the Z-axis value of each pixel.

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