mxcl/homebrew — pull request #15089 by gdelfino (2012-09-24 21:53:22+00:00)
Title: Imageworsener needs libpng

Without this, imageworsener is almost useless as it can not write png files:

$ imagew test-in.png -h 315 test-out.png
test-in.png -> test-out.png
imagew error: Writing PNG files is not supported.

With this change it works as expected.