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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. | 
