`i.layers "Optimize"` breaks PNG

Here's what I'm seeing now .

@jamesmusgrave May I ask what was the point of adding that option ? Here it doesn't seem to change anything (resize and crop work just as well, it only clobbers colors). I'm testing using imagemagick 6.8.9-5 and current HEAD (using Homebrew).

https://github.com/robwierzbowski/jekyll-image-tag/pull/20 <- reason for the code change. I'm not actively maintaining this plugin right now, so changes are accepted with trust that the community is checking them.

Optimize also breaks JPEGs (ridiculously badly looking photos)

After running a few tests here, I can't understand why the change was done : GIF images are perfectly resized and cropped without the code added by #20.