Indexed Color Systems

An 8-bit indexed image has a palette of up to 256 colors that the image can contain. Color information is not stored for each pixel, but rather just a reference to which color in the palette.

Palettes

• Exact (if 256 or fewer colors)
• Adaptive (weighted based upon colors in document)
• Web Palette (216 Web Safe Colors)
• System
  • Windows
  • Macintosh

But what happens to the other colors?

If you take a photo that is saved in an RGB system (millions of colors) and then convert it to an indexed system with 256 colors, what happens?

• dither
• color-shift