1. get the bootlogo file as PNG format. for example: logo.png (Note: the resolution of logo.png must be the same as the display panel's resolution)
2. Install imagemagick, using the convert tool (Ubuntu: sudo apt-get install imagemagick)
3. convert -depth 8 logo.png rgb: logo.raw
4. using the rgb2565 tool come with Android to generat initlogo.rle
/out/host/linux-x86/bin/rgb2565 -rle <logo.raw> initlogo.rle. (Note: the <> must be there)