What programs besides Photoshop are good for saving and optimizing images for web?
ImageMagick is a great tool to use that would require some understanding of how a terminal is to be used. However, the documentation is done very well so you can reference a lot of examples.
There was an article by Creative Blog that covered this back in January called: "The 18 best image file compression tools"
Pretty much any bitmap image manipulation software will do. It depends on how complex you want to go; how steep learning curve you are interested in.
Optimising for web is a bit of a misnomer these days: it is really hard to make bad images good regardless of software. As to file sizes and types, it is more dependant on loading times.
Some examples of software are Gimp, Paint and Irfanview.
Using ImageOptim on OSX never let me down so far. It's easy to use (drag-drop) and very efficient:
ImageOptim optimizes images — so they take up less disk space and load faster — by finding best compression parameters and by removing unnecessary comments and color profiles. It handles PNG, JPEG and GIF animations.
It bundles open-source (commandline) tools as far as their licenses allow:
ImageOptim seamlessly integrates best optimisation tools: PNGOUT, Zopfli, Pngcrush, AdvPNG, extended OptiPNG, JpegOptim, jpegrescan, jpegtran, and Gifsicle.
Furthermore, it can be integrated into a XCode workflow (iOS development and stuff).
In additon, ImageAlpha from the same author can be used to reduce 24-bit PNG images:
ImageAlpha greatly reduces file sizes of 24-bit PNG files (including alpha transparency) by applying lossy compression and conversion to a more efficient PNG8+alpha format. Such images are compatible with iOS, all browsers, and even degrade well in IE6.
I would recommend http://compressor.io/. It supports JPEG, PNG, GIF, and SVG which is super helpful when it comes to image quality (as well as lossless/lossy compression options).
Unfortunately you can't compress in bulk. For bulk optimization, you could try https://shrinkray.io/ (will compress all images, 50 at a time, in your repo).
I know it's crazy, but I like to mess around with some PHP image functions. Sometimes just running:
Can vastly reduce filesize.
Mess around with a few more functions, and I've managed to produce PNG files that even
pngcrush... only succeeds in making bigger.
If you're looking for a good PNG compressor, have a look to pngquant. It's very simple to use and very effective. I tried few other compressors, but they were either too complicated for me or less effective.
Another online tool: http://optimizilla.com
It provides manual quality control.
Now i use optimimage with nodejs, but i've used PNG Gauntlet for a lot.
There are many programs to do this. Like prepros and others.