Like other operating system, Android also used its own graphical image formats. Most of the images which are used in the OS are PNG files, but some of the Android phone uses the RLE image format for their kernal logos. The reason for using the RLE format is, that it provides pretty good compression ration and its very fast. Unfortunately, converting a PNG file to RLE is not easy and its require some tools. There are lots of tools available over the web, but not all of them are cross-platform and don't require ImageMagick to work properly
