PNG compression case study: Tweetbot for iPad

Is it me, or is it slightly worrying that a Twitter client (albeit a very nice one) needs 978 images amounting to 26MB in the original version? Regardless of the compressed PNG site, I guess all active images still need to be held in memory in raw form, taking up valuable device memory.

They have completely customized UI, so that's lots of images for button frames, normal/active icons, spinners, etc. Although some of them could be created programmatically, I suppose having separate files is much easier for designers.

Number of images is doubled, because they are regular and Retina versions.

And they don't have to be all in memory. You can reference image by name and let iOS read it lazily and flush from memory when necessary.

I'd be interested to see how (if at all) these optimisations in file size impact the battery life and performance. Alpha blending isn't free (though neither is overdraw), and using more CPU than 'disk' could use more power.

Though the differences could be lost in the noise.

Has anyone done these sorts of trials?

As I understand it, this is cheating— they used lossy compression on the PNGs to achieve the size reduction.