bmpsuite, by Jason Summers, is an excellent BMP test suite that covers many
obscure corners of the BMP format. All the test images can be seen here:

  http://entropymine.com/jason/bmpsuite/bmpsuite/html/bmpsuite.html

The code used to generate the test images is available here:

  https://github.com/jsummers/bmpsuite/

The readme.txt file states that the code is GPLv3 and the generated image files
are in the public domain. We have not included the code, but we have included:
(a) some quotes from the documentation and (b) some of the reference PNG
images. However, (a) and (b) are for testing purposes only and are not included
in Firefox releases.

The BMP files within this directory were generated with bmpsuite v2.3 (git
revision 3adcc9e20c0b6d2d665966b7e047b6f9474cef12).

There are three sub-directories.
- g/: for "good" images.
- q/: for "questionable" images.
- b/: for "bad" images.

Each file listed in a reftest.list file is annotated with the following lines.

- The first line starts with "BMP:" and is the output of the MOZ_LOG call in
  nsBMPDecoder.cpp. It has basic image info.

- Next is a quote from the bmpsuite docs, which describes the particulars of
  the file.

- Some files also have additional notes in square brackets. These explain
  anything non-obvious about the file, such as how we handle things that are
  ambiguous, any shortcomings in our decoding, and how Chromium handles the
  image.

Some of the reference PNGs need a small amount of fuzziness to match the BMPs.
This might be due to PNG color correction.