One such tool is PNGGauntlet. It is strongly recommended that you use it, as you may up to 60% compression of an image file.
Sunday, October 5, 2008
Optimize your images
Java ME applications may use images in the PNG (Portable Network Graphics) format, version 1.0, but at least the critical chunks must be present. As ancillary chuncks are not necessary you may use a tool to remove them.