/* Note: assumes little-endian byte order, 16-bit short, 32-bit int. */

    unsigned short width, height;
    unsigned int size, fullsize;

followed by <size> bytes of zlib compressed image data (which expands to <fullsize>)

the image data is a power of 2 square
2x2 4x4 8x8 etc

the largest size that encloses the actual image size

RGBA?
