Can't reduce PNG size in Windows

[anthony]

Windows and linux use different librarys. thus different sizes. Windows probably does not support all the compression modes of PNG so probably did not compress the image as well as the linux version.

Also you should read the image in first. If you don't read the image in first, commands are saved until one is read in. At that point the saved operations will be applied but without gurantee on their order. this is a special 'legacy' type mode.

See IM examples Basics