Better than ImageMagick: GraphicsMagick

They are pretty much the same, but GraphicsMagick's big CLI improvement over ImageMagick is that everything's based off an executable called 'gm'. IM's horribly generic 'convert' becomes 'gm convert', etc.

I'm not going to defend their CLIs beyond that though. The fact that 'mogrify' modifies an image file in-place and 'convert' doesn't has bitten me more than once.

Not another library, but a solution to the problem you mention. Capture each command line, even one-offs, in scripts. Then later you can reuse that script without having to figure out the command line options again.

You could say this is just shifting the problem to a new place: you now have to relocate the old scripts you wrote. Well, that's a much easier problem.

There's also FreeImage which works well with Image Science (a lightweight alternative to rmagick). It's what I use in almost all my production environments when I need performance over a ton of features.

Can you give a little more detail on Compass' CSS hooks and how you're using them, please?

GD2 has improved greatly with time (like adding gif support) but while I haven't tested them in about a year - ImageMagic/Graphics Magic uses much less memory for large images and outputs a much cleaner output. They also support a larger set of features and require less processing power.

It really depends on what you need them for - I'm not sure how to draw with imagemagic while I know how to do it with GD in php (though if you know neither I'd go with imagemagic). But whenever I need to generate thumbnails or work with photos I use imagemagic because I get a much better output quicker.