Perceptualdiff 1.1 Released

PerceptualDiff is an image comparison utility that makes use of a computational model of the human visual system to compare two images.

Added a few features at the request of the O3D team.
Added colorfactor and downsample options.
Also always output difference file if requested.
Always print out differing pixels even if the test passes.
Fixed bug in low light levels.

colorfactor - a float between 0 to 1. 0 means don't use color in determining differences.

downsample - how many powers of two to downsample images before running the test. i.e. -downsample 1 means scale the width and height by 0.5 before testing.