usage: mkshades <palette> [options]

    Generates a shade table to shade indices from a source palette into
    a destination palette.

        <palette>             Source palette
        -o <shade-table>      Output shade table pixmap
        -t <bits>             Generate true-colour shade table of 15,16 or 32 bits
        [-d <dest-palette>]   Destination palette if different from source
        [-n <num_shades>]     Number of shades to generate (default = 64)
        [-r <base>,<size>]    Range in output palette (default = 0,256)
