Hue Mapping

One of the simplest features is "hue mapping" or just color mapping (see HSV and HSL). Basically reddish colors match to reddish colors, etc. And what better way to show this than with candy (or flowers, but this time candy)! So, let's mess with skittles and combine these two images via hue:

What's happening here? Look at the colors in the worms and how they differ from the skittles. The program is looking at the colors from the worms and looking for similar colors in skittles and mapping them over. Reds are still reddish, blues a bit paler.

Here's another good example:

The blues gravitated towards some of the un-saturated concrete and the reddish colors to the fire-hydrant red.

One of the most interesting examples of hue mapping I've seen is this guy:

Sometimes hue-only mappings look awful—imagine if zero colors match. In this case, though, the results were beautiful and surprising. Note, the last image of the tree was the raw output of the program. Here is a more polished version using some post processing: