Description:

The main purpose of OptiPNG is to *optimize* PNG files, i.e. to reduce
their size to a minimum, without losing any information. In order to
achieve this goal, OptiPNG performs the following tasks:

- It losslessly reduces the bit depth, the color type and the color
palette of the image. This step reduces the size of the uncompressed
image, which, indirectly, reduces the size of the compressed image
(i.e. the size of the PNG file).

- It runs a suite of compression methods and strategies, and selects
the compression parameters that yield the smallest output file.