Natterings

Undocumented rgb2565 options

A quick note for Android hackers. If you’ve tried to customize the “boot image” displayed when you first power on an Android device, you’ve probably used the rgb2565 command-line tool at some point.

Out of curiosity, I checked the source, available from android.git.kernel.org. It’s pretty short and sweet. There are two undocumented options:

int main(int argc, char **argv)
{
    if ((argc == 2) && (!strcmp(argv[1],"-rle"))) {
        to_565_rle();
    } else {
        if (argc > 2 && (!strcmp(argv[1], "-w"))) {
            to_565_raw_dither(atoi(argv[2]));
        } else {
            to_565_raw();
        }
    }
    return 0;
}

By default, rgb2565 will convert your image to 565 format.

-rle will run-length-encode it

more usefully, the -w option will dither it, which should reduce banding artifacts from blindly converting from an 888 24-bit png to the more restricted 16-bit 565 format.

You can find some more information here but it may not apply to all Android platforms. Caveat Emptor.

Okay, more iPhone Tech Talk Notes on the way.