In computer graphics, a color look-up table, or CLUT, is the set of available colors for a given application.
For example, a 24-bit 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 CLUT in this case would consist of the 16 million colors, but the program’s palette would contain only the 256-color subset. To avoid dithering (i.e., varying the pattern of dots in an image) on 8-bit machines, you should only use colors from a predesignated CLUT.
CMYK stands for cyan magenta yellow and blacK and is a color system used in the offset printing of full-color documents.
Offset uses cyan, magenta, yellow, and black inks and is often referred to as “four-color” printing. Monitors use red, green, and blue light instead, so they display images using a different color system called RGB. One of the great problems of the digital age has been matching colors between these two systems; i.e., taking a digital RGB image and making it look the same in print using CMYK. These problems are addressed by applications such as the Pantone Matching System.
A grayscale image uses only shades of gray to represent an image.
Black-and-white photographs can use a virtually unlimited number of shades of gray, but most computers can display only 16 or 256. To grayscale is to convert a continuous-tone image, like a black-and-white photograph, to an image made up of pixels. Grayscaling is different from dithering, which uses either black or white pixels next to one another to simulate shades of gray. In grayscaling, each individual pixel can be a different shade of gray.
The hexadecimal (base 16) number system used for Web-page design consists of 16 unique symbols:0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, and F.
For example, the decimal number 15 is equal to the hexadecimal number F. In HTML, an RGB
color can be designated by
with the first two numerals representing the amount of red, the second two the amount of green, and the last two the amount of blue. If you wanted your background to be red, you could write the code for a body background color as
Black is the absence of all color and white is the presence of all color, so in hexadecimal, black is at the bottom of the system (no red, green, or blue:
and white is at the top (the maximum amount of red, green, and blue:
Much like an oil painter with her palette of many unique color combinations, each operating system has its own palette. Many computers out there display only 256 colors at a time, and the Macintosh and Windows operating systems reserve about 40 colors out of the 256, leaving 216 available. Netscape Navigator, Microsoft Internet Explorer, and NCSA Mosaic implemented a 216-color palette that won’t dither (i.e., vary the pattern of dots in an image) on different platforms and is “browser safe” (in other words, these 216 colors will always look the same, no matter what platform or browser is being used). Theoretically.