Influence the Colour Range in 8-bit Graphics
Update! This article was written for Photoshop CS3. It would appear CS5 does not offer the same functionality.
This is a neat little technique I stumbled upon one day while poking around in Photoshop’s “Save for Web…” settings. It allows weighting of Photoshop’s colour palette when saving 8-bit images. As with a lot of discoveries in life, it wasn’t long before I found it coming in very handy.

Saving this graphic for web as an 8-bit image was creating a lot of undesirable banding in the gradients of the coloured twirls. (Saving as a 24-bit image was out of the question given the file size. Saving as .jpg could be a consideration, but as we shall see, not necessary.)

The PNG and GIF compression algorithms determine their palettes based on frequency of each colour. So in this case the blacks and greys are over represented, while the pinks and blues (and to some extent yellows) are under represented. That’s why the banding is most obvious in the colourful sections of the graphic.
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