punypng is a free web-based application which can seriously compress JPG, GIF & PNG images without any loss of quality. The application first analyzes the content of your image and figures out the best image format to use. If necessary, converts the format automatically.
It also has built-in support for dirty transparency* which can save an average of extra 10% for transparent GIF & PNG files. What would be more amazing is the service to offer a desktop tool with context menu support. *: an innovative technique that offers additional compression to any PNG or GIF as long as it has either 8-bit or 1-bit transparency
Image Optimizer, is a free online service, which you can resize, compress and optimize your image files. Optimized images are better! They are more suitable for web pages, email attachments, or even storage on your disk.
Online Image Compression is used to compress (or convert) images into the JPG image format. But whatever kinds of images I uploaded, the compressed images were larger than the original ones.
Smush It allows you to compress the online images “lossless”, the GIF file will be converted to PNG file once compression.
Dymanic Drive can either enter an image URL or upload an image to be compressed, and you can also convert the image to JPG, GIF or PNG file. There are different compressed images with different qualities for preview before downloading.
