GotOnTheInter.Net: Random Babble and Misc Adventures

So you want to join the party and flash your own boot image, but its a weird undocumented format and you don't want to spend all year researching it in the source. Well, I'm here to help.

It is actually very simple. Start with an image you want to use, make sure it is 320x480 with 8bpp color. (In my examples, I'll use splash.png: PNG image data, 320 x 480, 8-bit/color RGBA, non-interlaced
Just make sure you have ImageMagick installed, and the utilities from the source build. (Specifically, rgb2565.)

$ convert -depth 8 splash.png rgb:splash.raw
# Make sure it is 460800 bytes long!
$ rgb2565 < splash.raw > splash.raw565
# Triple-check size before flashing! 307200 bytes
$ fastboot flash splash1 g1-splash.raw565
$ fastboot reboot

Lets break it down. the convert turns it from a png (or any supported image format) into a raw 8-bits-per-color no-alpha data file. This file should be 460800 bytes - no more, no less.

Next, rgb2565 converts that file to a raw 565 16bit file (for the framebuffer on the G1.) This file is exactly 307200 bytes long - if its not, you messed up somewhere.

Finally, you use fastboot to flash the splash image and reboot. Instead of the B&W T-mobile logo, now you will see your custom splash screen. Congrats! :)