pngquant changes pixels in the image, which gives it freedom to make files much, much smaller than the completely lossless pngcrush can (60-70% vs 10-30%). pngquant-converted files can still be pngcrushed to make them even smaller.
> are you not able add this as a build step?
I am, but I think it's a shame that it's needed. I think users should be able to trust that their apps produce good output in the first place, and not need to hook up 3rd party tools to compress the files well.
What ever happened to "Small tools that do one thing well"?
ImageOptim is extremely well-known in the industry. I'd much rather the developers of my vector drawing tool focus on making a great vector drawing tool, and let [you] obsess over making the best image compression tools. It's not just as simple as just bundling pngquant into the export process. You also have to make an effective UI that implicitly explains to users, "You know that lossless PNG image format you love? Well, here's a slider to make it do lossy compression!"
My preference would be, don't even have an Export For Web option. Or if you do have it, just make it link to ImageOptim!
(Edit: Didn't realize who I was responding to. My team loves and lives by ImageOptim and ImageAlpha — thank you for them! Even if Sketch had better PNG export, we'd still be using your tools as part of our development process to deal with all the other programs that don't get it right.)
pngquant changes pixels in the image, which gives it freedom to make files much, much smaller than the completely lossless pngcrush can (60-70% vs 10-30%). pngquant-converted files can still be pngcrushed to make them even smaller.
> are you not able add this as a build step?
I am, but I think it's a shame that it's needed. I think users should be able to trust that their apps produce good output in the first place, and not need to hook up 3rd party tools to compress the files well.