The BODY contains pixel data for the image.  Width, Height, and depth
(Planes) is specified in the bmhd.

If the bmhd compression byte is 0, then the scan line data is not
compressed. If Compression=1, then each scan line is individually
compressed as follows:

    while (not produced the desired number of bytes)

            /* get a byte, call it N */

            if (N >= 0 && N <= 127)
                    /* copy the next N+1 bytes literally */

            if (N >= -127 && N <= -1)
                    /* repeat the next byte N+1 times */

            if (N == -128)
                    /* skip it, presumably it's padding */