Harvard Extension School
CSCI E-12 Fundamentals of Web Site Development | Fall 2019

## 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

Copyright © David Heitmeyer