glbench_knownbad_images   ... directory with images of known bugs
glbench_reference_images  ... good images
glbench_sample_testoutput ... unsorted output from sample test runs (human consumption only)

These directories contains reference images for graphics_GLBench test.  After
uncompressing to RGBA these images will match the checksums in their name:
For example:

    > convert mpixels_sec_clear_color.pixmd5-e3609de122a164fe240a562c69367de.png rgba:- | md5sum
    e3609de1022a164fe240a562c69367de  -

Combining test name with MD5 makes it possible to keep multiple versions
of reference images in the same directory. Also checking against reference
images becomes a simple file existence test.

The "convert" tool comes from the imagemagick package.