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Chapter 22. Designing Graphics with the ... > Converting to the Web Palette

22.2. Converting to the Web Palette

Designing with web colors is one method to prevent dithering. The other opportunity is to add (or preserve) web-safe colors in the conversion process from RGB to Indexed Color. As part of this process, you will be asked to select a palette for the image. The colors from the palette will be used to approximate the full color range from the original RGB graphic. See Common Palettes for descriptions of palette options in popular graphics programs.

Sidebar 3. Common 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. There are several standard palettes you can choose from within popular graphics programs.


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.


This is a custom palette generated with the most commonly used pixel colors in the image. 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-shifting will occur.

Perceptual (Adobe Photoshop/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 than adaptive palette images.

Selective (Adobe Photoshop/ImageReady only)

This is similar to Perceptual, but it gives preference to areas of broad color and the preservation of web-safe colors. It is the preferred palette for web graphics created with Photoshop/ImageReady.

WebSnap Adaptive (Macromedia Fireworks only)

An adaptive palette in which colors that are near in value to web palette colors are converted to the closest web palette color.

System (Mac/Windows)

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


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


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

Optimized Median Cut (Paint Shop Pro only)

This reduces the image to a few colors using something similar to an adaptive palette.

Optimized Octree (Paint Shop Pro only)

Use this palette if the original image has just a few colors and you want to keep those exact colors.



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