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Thread: PNG files re compress?

  1. #1
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    Default PNG files re compress?

    Hello

    Wondered when you open a png in Photoshop CS 1, and alter it then save it, does the png file get re-compressed further, each time you change and save it or does it remain the same?

    Thanks
    KB

  2. #2
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    It shouldn't. And if it does there's something wrong, because it saves by the file's width/height/detail etc.
    So it should remain the same.
    - Mike

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    That's good news thanks...

    KB

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    It would be nice if it did, but no

    PNG is a lossless algorithm; its compression does not affect the image's quality.
    Twey | I understand English | 日本語が分かります | mi jimpe fi le jbobau | mi esperanton komprenas | je comprends franšais | entiendo espa˝ol | t˘i Ýt hiểu tiếng Việt | ich verstehe ein bisschen Deutsch | beware XHTML | common coding mistakes | tutorials | various stuff | argh PHP!

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    Actually, there can be some truth in "recompressing", as newer algorithms (never versions of libbz2) have improved strenght due being more optimised- you can get PNG recompressed to lesser filesize with newer software (but of coure there's sometimes an absolute limit- usually 92-94 bytes in my test cases for files that had more than one pixel)

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    pngcrush is always worth looking into. It doesn't have much of an effect on GIMP-created PNGs (I guess they're already optimised to the limit), but I hear it has quite an effect on Photoshop-engineered ones.
    Twey | I understand English | 日本語が分かります | mi jimpe fi le jbobau | mi esperanton komprenas | je comprends franšais | entiendo espa˝ol | t˘i Ýt hiểu tiếng Việt | ich verstehe ein bisschen Deutsch | beware XHTML | common coding mistakes | tutorials | various stuff | argh PHP!

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