This is terrible advice. Dithering should not be used for compression. Real world example: Here's his dog picture encoded to webp using default settings (11KB)

This is terrible advice. Dithering should not be used for compression. Real world example: Here's his dog picture encoded to webp using default settings (11KB): https://image.non.io/dog.webp https://image.non.io/dog.webp This is smaller than all but his two color and his four color examples, at a tremendously higher fidelity. Just for comparison: webp vs original @ 11KB: 2.1% difference from source image. gameboy vs original @ 8KB: 18.2% difference from source image. 4 color vs original @ 9KB: 15.2% difference from source image. Even if you compress the webp down to 8KB, you only encounter a 3.3% difference from the original. TL;DR - use modern image formats. Don't use dithering for compression.