If you find some interesting images on the web,want to optimize and use them for shortcuts icons.Or you just want to compress some pictures,you can try Trimage,a cross-platform tool.

Trimage’s homepage says:

Trimage is a cross-platform GUI and command-line interface to optimize image files via optipng, advpng and jpegoptim, depending on the filetype (currently, PNG and JPG files are supported). It was inspired by imageoptim. All image files are losslessy compressed on the highest available compression levels. Trimage gives you various input functions to fit your own workflow: A regular file dialog, dragging and dropping and various command line options.

Install Trimage image compressor in Ubuntu:

Ubuntu 9.10 and higher users can easily install Trimage by following commands in Applications->Accessories->Terminal:

sudo add-apt-repository ppa:kilian/trimage
sudo apt-get update
sudo apt-get install trimage

In Ubuntu 9.04 and earlier version,read this guide on installing PPA’s.

This is Trimage’s main window:

If you’re on other system and want to try Trimage image compressor,go to http://trimage.org/