Binary package “optipng” in ubuntu natty
advanced PNG (Portable Network Graphics) optimizer
OptiPNG is a PNG optimizer that recompresses the image files to a smaller
size. It losslessly reduces the bit depth, the color type and the color
palette of the image, runs a suite of compression methods and strategies,
and selects the compression parameters that yield the smallest output file.
It also recognizes several external file formats like BMP, GIF, TIFF and
PNM (PBM, PGM, PPM).