Glossary of Terms
Select the first letter of the word from the list above to jump to appropriate section of the glossary. If the term you are looking for starts with a digit or symbol, choose the '#' link.
Bit resolution
also called bit depth, measures the number of bits of stored informationper pixel. This resolution determines how many colors can be displayed at one time on-screen (that is, 8-bit,24-bit, or 32-bit color. Adobe Photoshop Training Workbook
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.
Window's bitmap. BMP is the native image file fomat that works with Microsoft's Paint program included under Windows 95. This format can be opened by both Windows and DOS platforms as well as in major image editing programs like Adobe Photoshop. BMP images can be saved in millions of colors, although this is more than is humanly perceptible for display on monitor screens. BMP also supports a compression scheme known as RLE or Run-Length Encoding, which operates similarly to GIF's LZW compression scheme. See GIF below for more detail on LZW compression.
Cache
A hidden collection of documents viewed from the Internet. Your cache needs to be emptied on a regular basis. If you run a MAC you may go to the preference or settings menu of your browser. When you find the cache, clear it. If you run Windows 95-98 the procedure is a little more complicated. First you will need a leave of absence from work.
Contrast
The juxtaposition of dissimilar elements in a work of art. Contrast is used to draw attention to the differences in colors. It makes an object stand apart. Contrast elivens a picture through the use of value, hue, satauration, complementarky contrast and warm and cool contrasts.In a basically light composition, dark areas will attract attention. In a predominately dark composition, light attracts. Where black and white meet is the area that draws the most immediate attention. Remember to soften the degree of contrast between text and background to soften the visual stress.
digital
A form of representation in which distinct objects, or digits, are used to stand for something in the real world,
so that counting and other operations can be performed precisely. Data represented digitally can be
manipulated to produce a calculation, a sort, or some other computation. In digital electronic computers, two
electrical states correspond to the 1's and the 0's of binary numbers, which are manipulated by computer
programs.
digitize
To translate into a digital form. For example, optical scanners digitize images by translating them into bit maps. It is also possible to digitize sound, video, and any type of movement. In all these cases, digitization is performed by sampling at discrete intervals. To digitize sound, for example, a device measures a sound wave's amplitude many times per second. These numeric values can then be recorded digitally
dpi
Abbreviation of dots per inch, which indicates the resolution of images. The more dots per inch, the higher the resolution. A metric used to measure print and screen resolution. A common resolution for laser printers is 600 dots per inch. This means 600 dots across and 600 dots down, so there are 360,000 dots per square inch.
Font
Usually refers to a face, which is the entire family of letters (and numbers, punctuation, etc.) of a particular shape or design.
There are two broad categories:
Bitmap or raster fonts
Scalable or outline fonts
While scalable fonts are usually more desirable (because you can adjust thesize while maintaining theproportions and smooth edges), bitmap fonts are required for raster devices,such as computer monitorsand dot matrix printers.
Software such as Adobe Type Manager (ATM, for PostScript Type 1 Fonts) and Microsoft's TrueType (for its TrueType Fonts) can convert scalable fonts to bitmap fonts. The accompanying figure shows the common types of fonts currently available
GIF
Graphic Interchange Format. This is the most widely recognized graphic format on the Web. GIF image types are usually best suited for any images other than ones photgraphic in nature (i.e. solid color illustrations, clip art, text graphic images, diagrams, etc.). Gif Converter (Macintosh) or LViewPro (Windows) are useful programs that allow you to convert other images into GIF images, to use in WWW documents. The GIF format was incorporated by Compuserve in the 1980's and utilizes a compression scheme called LZW, named for it's creators, Lempel-Zev-Welch. This LZW compression looks across your image in a line by line fashion for large areas of like color (pixels with the same value). The compression algorithm squeezes these runs in a horizontal fashion by simply looking at the first pixel in the run and repeating it a specific number of times.This compression is lossless in nature, thus it maintains its original clarity during decompression. All GIFs are limited to a maximum of 256 colors, or 8-bit "Indexed" image color.
The GIF 89a file format incorporates the ability of transparency in the image, along the ability to layer different images into a single image. Combining these two features one is able to create the "Animated GIFs" so widely found on the web today. Most of the advertisment banners that adorn the top secton of many web pages are animated GIFs. These animations are quite easy to create making simple use of a "flip book" style of animation. An awesome MAC freeware utility available on the web is Yves Piguet's program called GifBuilder 0.5. With this program one can import simple GIFs and adjust their position, transparency, looping, and frame transition features. GIFConstruction Set is a similar program for Windows PC platform..
One last feature often used in GIFs is "Interlacing". A GIF has interlacing incorporated into its format when the image first appears fuzzy or blurry when downloading, and gradually focuses into a sharp image. This allows the user to preview the image while downloading instead of waiting for the entire image to download first.. It is generally not a good idea to have an image incorporate both interlacing and transparency at the same time. For a detailed explanation of GIF and JPEG images check out the Web Graphics chapter in the The Yale C/AIM Web Style Guide.
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.
The following are also considered graphics applications :
In general, applications that support graphics require a powerful CPU and a large amount of memory. Many graphics applications -- for example, computer animation systems -- require more computing power than is available on personal computers and will run only on powerful workstations or specially designed graphics computers. This is true of all three-dimensional computer graphics applications.
In addition to the CPU and memory, graphics software requires a graphics monitor and support for one of the many graphics standards. Most PC programs, for instance, require VGA graphics. If your computer does not have built-in support for a specific graphics system, you can insert a video adapter card.
The quality of most graphics devices is determined by their resolution -- how many points per square inch they can represent -- and their color capabilities.
image
A picture, idea, or impression of a person, thing, or idea; or a mental picture of a person, thing, or idea. In graphic interpretation, any abstract or realistic representation of an idea.
JPEG
Joint Partner Experts Group or Joint Photographic Experts Group.This is the second most widely used format for the web.A variable compression image format that supports true color images in 16 bit (thousands) or 24 bit (millions) of colors. JPEG compression offers a larger compression of images than GIF compression, thus making image file sizes smaller and faster for transfer on the web. Although, the compression scheme that JPEG uses is a lossy one. That means that once one compresses an image using JPEG compression, resolution or sharpness once present in the original image will be lost forever. The compression algorithm JPEG uses is especially designed for pictorial images, sorting together likes areas of color in an image, and throwing away subtle differences in color the viewer cannot distinguish between. The JPEG format is great for photographs, but should there be large one color solid areas in your image a blemish known as an artifact may appear. Experiment with the various compression settings, for one will be able to notice the differences between high compression (smaller file size and low image quality) and low compression (large file size and high image quality). You determine the balance.
The idea behind saving a photographic image in JPEG is this: make a copy of the original high quality image. Use this copy to save in various JPEG compression settings, changing the name while saving, so as to protect the quality of the copy. Compare acceptible JPEG compression schemes, selecting the one balancing file size and image quality.
It should be noted that JPEG images at present do not support transparency layers as do GIFs. So simple image animation is reserved for GIF images only. JPEGs do however support a unique type of interlacing called Progressive JPEGs. Here the image is decompressed in alternating successive scans such that the image may be previewed in a blurry format while initially downloading. Most current browsers at the 3.0 version or later support the display of Progressive JPEGs. To save a JPEG in this format one must have an image software program that supports saving in this file type. For a detailed explanation of GIF and JPEG images check out the Web Graphics chapter in the The Yale C/AIM Web Style Guide.
Metafile
A metafile is a file containing information that describes or specifies another file.
Microsoft uses this term for its Windows Metafile (WMF) format. A WMF file contains a sequence of graphical-device-interface (GDI) function calls ("commands" to the Windows operating system) that results in the presentation of a graphic image. Some of the function calls are equivalent to vector graphic statements and others identify stored bitmaps or literal specifications of which bits to illuminate (rasterized images). Using WMF files rather than already-built bitmaps saves space when many bitmaps are used repeatedly by different components of the operating system or of an application. The WMF file assumes a 16-bit operating system. Microsoft has an enhanced metafile (EMF) format for its 32-bit operating systems. Microsoft's clipboard (CLP) file can contain a WMF file, an EMF file, or a bitmap (BMP) format file.
Another example of a metafile is the Computer Graphics Metafile (CGM). The CGM file format is a standard (ANSI-approved) format that can be used on any operating system that supports it (unlike the WMF format which is designed only for Windows). The CGM file is commonly used in CAD and presentation graphics applications.
multimedia
In personal computing, software and applications that combine text, high quality sound, graphics, and animation or video.
Neutrals
The gray colors
PICT
Macintosh Picture format. PICT formatted images are the native image file format for all Macintosh computers. PICT formatted images can be saved in any color depth, size, or resolution. This Mac native image file type cannot be viewed on the Internet via a browser or on most PC machines (unless they have quicktime installed). Pict compression (16 or 32 bit) is one option presented with PICT images, but it's compression is not a good as the JPEG compression option available when saving PICTS.. Should you be using this image type only in a Macintosh environment, you'll be fine importing this image type into a wide variety of software applications, like: Clarisworks, Microsoft Office, Appleworks, or Adobe Photoshop.
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 1,024 by 768, or nearly 800,000 pixels. True Color systems use 24 bits per pixel, allowing them to display more than 16 million different colors.
PDF
Making this possible is a freeware standalone program called Acrobat Reader 3.0. There is also an Internet plug-in Adobe distributes with Acrobat Reader which allows the user to view PDF documents from directly within their Internet browser. Although the plug-in is user friendly, it is wise to save the desired PDF as a separate file to one's desktop and view via the Acrobat Reader stand alone program.
The exciting thing about PDF documents is that they are vector-based. This means the user can view the documents at any level of magnification, zooming in to say 600% with the document sill in vivid clarity. All original formating as created by the designer is maintained via the PDF format. To create PDF documents one needs to purchase the Acrobat 3.0 suite of software which contains Acrobat Exchange for viewing and editing existing PDF doucments, as well as The PDF Writer and Acrobat Distillerfor creating PDF doucments.
Plotter
A device that draws pictures on paper based on commands from a computer. Plotters differ from printers in that they draw lines using a pen. As a result, they can produce continuous lines, whereas printers can only simulate lines by printing a closely spaced series of dots. Multicolor plotters use different-colored pens to draw different colors.
In general, plotters are considerably more expensive than printers. They are used in engineering applications where precision is mandatory.
Primary
Red, yellow and blue colors.
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.
Scanning
Scanning an image into your computer is merely taking a snapshot of whatever is on the scanner glass and digitizing this image such that you are now able to manipulate it via some image editing software program. Light is projected through the scanner glass onto an object placed atop the glass. As the light strikes the photograph, line drawing, or 3-D physical object atop the glass, it is reflected off this object and back down into the optics beneath the glass inside the scanner. This reflected light from the object is electronically captured by the scanner and digitized for viewing and manipulation. This is very similar to how an ordinary camera captures light reflected off an object (either by natural light, or photographic flash bulbs) and saves this refected light coming back through its optics or lens onto film.
The major difference in the digital image, is that the user can use the software included with the scanner to manipulate the size, file type, resolution, color depth, brightness, etc. of the image even before saving it to his/her computer. Similarly this image can then again be manipulated in ones computer via a separate image editing program like Adobe Photoshop, Clarisworks Paint, Appleworks Paint, Corel Draw, or Microsoft Accessories Paint software. For more information on scanning images into your computer be sure to check out ScanTips.Com.
Schema
Pronounced "skeema." The definition of an entire database. Schemas are often designed with visual modeling tools, which automatically create the SQL code necessary to define the table structures. See subschema. ERWIN.WMF Building an Entity Relationship Model The Erwin modeling program from Logic Works, Princeton, NJ, stands for Entity Relationship for Windows. In this order processing example, the tables for customers and orders are drawn graphically, and Erwin turns the graph into the appropriate SQL code for the target database. (Example courtesy of Logic Works, Inc.)
Secondary Colors
Colors that are made by mixing two primaries. Orange (red and yellow), green (yellow and blue), purple (blue and red).
Shades
Pure hue mixed with black.
Style sheets
In word processing and desktop publishing, a style sheet is a file or form that defines the layout of a document. When you fill in a style sheet, you specify such parameters as the page size, margins, and fonts.Style sheets are useful because you can use the same style sheet for many documents. For example, you could define one style sheet for personal letters, another for official letters, and a third for reports. Stylesheets are also called templates. On the World Wide Web a style sheet refers to cascading style sheets.
Tertiary
Mixing six colors between the primary and secondary colors.
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
TIFF
Tagged Image File Format. TIFF formated images are bitmapped images that use true 24-bit (millions) of colors. The compression used by TIFF formated images is lossless, thus one does not degrade their image when saving in the TIFF format (unlike the case with the JPEG format). TIFF images therefore are usually reserved for high quality and those wishing to print their images at some point in time. Tiff images are compressed using the LZW compression algorithm similar in nature to GIFs. The file sizes are extremely large and not appropriate nor compatible for use over the Internet, or for use in electronic presentation (screen only display). Remember that the maximum avaerage resolution that can be rendered on the majority of computer screens is 72 dpi. Saving an image at 360, 720, or 1200 dpi regardless of image file type would be a tremendous waste of space, download time and CPU processing power.
Tints
Mix of pure hue with white.
Tone
Pure hue mixed with a gray.
.WMF
A metafile is a file containing information that describes or specifies another file.
Microsoft uses this term for its Windows Metafile (WMF) format. A WMF file contains a sequence of graphical-device-interface (GDI) function calls ("commands" to the Windows operating system) that results in the presentation of a graphic image. Some of the function calls are equivalent to vector graphic statements and others identify stored bitmaps or literal specifications of which bits to illuminate (rasterized images). Using WMF files rather than already-built bitmaps saves space when many bitmaps are used repeatedly by different components of the operating system or of an application. The WMF file assumes a 16-bit operating system. Microsoft has an enhanced metafile (EMF) format for its 32-bit operating systems. Microsoft's clipboard (CLP) file can contain a WMF file, an EMF file, or a bitmap (BMP) format file.
Another example of a metafile is the Computer Graphics Metafile (CGM). The CGM file format is a standard (ANSI-approved) format that can be used on any operating system that supports it (unlike the WMF format which is designed only for Windows). The CGM file is commonly used in CAD and presentation graphics applications.