* Ron Bickers <rbickers-dated-999542769.b3b605@logicetc.com> [010827 19:55]:
So maybe you could give a look at ImageMagick, especially the "mogrify" command. I've used it only from os.system, but AFAIK there's a python module for ImageMagick which may produce better results than PIL (untested), it's called PyMagick IIRC.
I've been running some tests with my Photo product that uses PIL and comparing it to the output of mogrify and I can barely tell any difference in any of the rendered images. I've resized 1024x768 JPG to 480x'whatever' and 128x'whatever' and I don't see enough difference to say ImageMagick is better. In fact, parts of the image seem better with PIL and other parts with IM. Am I missing something? What options should I be using for mogrify?
I'm afraid I just don't have time to gather the evidence right now, but unless I've made some huge mistake, there are definitely problems with the PIL resizing output quality - I've seen 'jagged edges' too. The tests you mention are scaling images by powers of two (i.e. 480 = 1024 / 2, 128 = 1024 / 2^3) which will minimise the number of rounding errors (I'm guessing a bit - can you tell? ;-). Have you tried scaling down by 1/3, 1/7, etc?
If people are disatisfied with PIL resizes, I'd like to provide an alternative, but IM isn't nearly as Python friendly.
I'm still not clear of the _disadvantage_ of having to do an os.popen() call, or similar? cheers, seb