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What is a good free program for loss-less image compression? Must be open source.

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2 Answers 2

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There are any number of image manipulation programs that will save images in lossless compressed formats such as png or gif:

are the ones that spring to mind straight away.

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hmm but can i do lossless image compression in png? –  senzacionale Mar 22 '11 at 16:16
@senzacionale - png is lossless by definition. –  ChrisF Mar 22 '11 at 16:17
thx didn't know that. I also found some good png optimizer: psydk.org/PngOptimizer.php –  senzacionale Mar 22 '11 at 18:26
I know what you meant - gif compression doesn't throw away any info from a 256 color image - but I'd like to remind readers that converting a (potentially 16 million color) photo to 256 colors (for a gif or whatever) is lossy. 24-bit png is the way to go. –  Rich Homolka Mar 22 '11 at 18:38

Irfanview will do it.

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