Web Design in a Nutshell

Other Palettes

All 8-bit Indexed Color images (such as GIF or PNG-8) use a palette of colors to define the colors in the image. The Web Palette is just one of infinite palette possibilities. However, there are several standard palettes you can choose from within popular graphics programs. This section defines the common palette choices that will be referred to throughout this chapter.

Exact

If the image contains fewer than 256 colors, choosing the Exact palette option makes a palette out of the actual colors that are found in the image.

Adaptive

This is a custom palette generated using the most commonly used pixel colors in the image. Less commonly used colors are approximated by the most commonly used colors. It allows for color-depth reduction while preserving the original character of the image. Because the number of colors is being reduced, some dithering and color-shifing will occur.

System (Mac/Windows)

Choosing either system palette will convert the image to the palette of 256 colors as defined by each operating system.

Uniform

This palette contains an evenly stepped sampling of colors from the RGB spectrum.

Custom

This allows you to load in a palette that was previously saved and apply it to the current image.

Perceptual (Adobe ImageReady only)

This creates a custom palette by giving priority to colors for which the human eye has greater sensitivity. Unlike Adaptive, it is based on algorithms, not just a pixel count. It generally results in images with better color integrity ...