Running a high trafficed platform. In my quest to minimise bandwidth costs, I added a high JPEG compression on all JPEG uploads (check solution in my previous question). However, WordPress does not convert PNG files to JPEG, which means that all PNG files remain at their original size.

Is it possible to make all PNG uploads be converted to PNG-8 format? PNG 8-bit is limited to 256 colours which should bring down the file size quite drastically.