by Rickard Westerlind on WordPress.org
Improve the quality of re-sized images by replacing standard GD library with ImageMagick.

Administration interface
Dramatically improve the quality of re-sized images by making WordPress use ImageMagick instead of standard GD image library.
Features
Lnguages: English, French, German, Swedish, Turkish
Requires either ImageMagick binary or Imagick PHP module.
Code repo available on https://github.com/orangelabweb/imagemagick-engine/