Quantization, involved in image processing, is the process seeking to reduce the number of colors required to represent an image. Although more frequent in the past, currently color quantization is only used in 8-bit (256 color) images, as GIF images and some PNG images.

A standard quantization algorithm works in 2 steps:

1. Analyze the image to select the new color palette. Usually, this involves checking each pixel to choose the most frequent colors.
2. Dither the image to the new color palette.

Quantization algorithms

An usual quantization algorithm is the Octree-based algorithm, as described in the MSDN article on ASP.NET color quantization