Optipng

OptiPNG will also help you convert external formats (GIF, PNM, BMP, and TIFF) to optimized PNG, and will perform PNG integrity checks and corrections. 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... Platforms: Windows

Provides API to optimize PNG images using OptiPNG. Platforms: PHP

PNGPress is a frontend for OptiPNG. It takes one or more image files and squeezes every last kb out of them, without "losing" any data. Just drag your images onto the PNGPress icon, and away it goes. PNGPress will also backup your original images, and allows you to set the compression level... Platforms: Mac

This is a toolkit for ImageAPI. It requires imageapi_gd or imageapi_imagemagick or any ImageAPI toolkit to work.ImageAPI Optimize allows you to use your preferred toolkit and optimize (losslessly) the image when it is saved. Practice for web performance suggests that images should be optimized... Platforms: PHP

PNGCrusher is a simple app that optimizes the filesize of PNG images. Just drag any number of PNG files onto the app and they will be processed by the open source OptiPNG, which provides better compression rates than the standard pngcrush. If you deal with png images a lot, especially in web... Platforms: Mac