What is Run-length Encoding?
Run-length encoding (RLE) is a lossless compression method where sequences that display redundant data are stored as a single data value representing the repeated block and how many times it appears in the image. Later, during decompression, the image can be reconstructed exactly from this information.
This type of compression works best with simple images and animations that have a lot of redundant pixels. For complex images and animations, if there aren't many redundant sections, RLE can make the file size bigger rather than smaller. Thus it's important to understand the content and whether this algorithm will help or hinder.
This technique was first patented by Hitachi in 1983. It's less popular today because there are other more advanced options available, but you will still find it in use for color for fax machines, icons, line drawings and simple animations.