Post any defects you find in the released or beta versions of the ImageMagick software here. Include the ImageMagick version, OS, and any command-line required to reproduce the problem. Got a patch for a bug? Post it here.
What software made test.png? Why does it have gamma=2.2 instead of the more usual 1/2.2? Some software will ignore this setting and assume it is really 1/2.2. Other software, like Firefox and ImageMagick, will use this setting and so it appears bright.
The cure is to put the proper setting into test.png.