Among the popular image formats is the PNG image format or popularly known as Portable Network Graphics. This Image format is better than JPG in terms of picture quality as it don’t compress image but this is the reason for its large size too.
Here is a tool called Pngcrush that can reduce the size of the PNG images. Pngcrush is an optimizer for PNG files. Its main purpose is to reduce the size of the PNG IDAT data stream by trying various compression levels PNG filter methods. It can be run from a command line in an MSDOS window, or from a UNIX or LINUX command line.
This freeware is very useful to those who want to use the images in the PNG formats but don’t want its size to be much. Pngcrush is an open-source tool and can be downloaded from the link below.