This sub-menu contains a single color effect: Quantize.
This effect reduces the number of colors in an image. Quantization is sometimes called “palettization”; the process of recoloring a full-color image with a smaller number of shades, thereby reducing the total color range.
Two algorithms are given, Median Cut and Octree. Both reduce the palette to 256 shades or less, and both have nine levels of dithering. Octree deals better with images that have a large number of colors. It produces good results with little degradation when converting from a high number of colors to something more reasonable. The downside is that it's a more computationally expensive algorithm, which means that it will typically take longer than Median Cut algorithm to quantize the same image. The name Octree comes from the data structure that is used to represent the colors of the image. It is made up of a number of nodes, each of which has up to 8 children.