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Thread: where to get source code for a jpeg implementation?

  1. #1
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    where to get source code for a jpeg implementation?

    I am looking to try out some ideas to see how much they could improve on JPEG's compression efficiency. These ideas are modifications to the core algorithms of DCT and entropy coding.

    What do you suggest is the best way to implement these ideas and compare them to the performance of existing standard implementations? Matlab, Octave, or C? I did look up the libjpeg implementation in C.

    Basically I want to do a thorough statistical comparison between my ideas and the standard JPEG, in order to decide if it is worthwhile to pursue these ideas further. I am aware that this is indeed a crowded old research field with innumerable overlapping ideas since Shannon. And that it is a patent minefield.

    Should I take any existing open source implementation of JPEG and then modify that code to add my own ideas? Or is it better to implement the code myself in Matlab or Octave? I have already been playing around in Octave code to statistically analyse test images w.r.t my ideas.

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    It would be faster to use a preexisting code then modify it. But if you can make your own code it would be easier to implement your ideas since it's written in a way you understand.
    If you're looking for open source jpeg implementations there are plenty out there, I'd recommend choosing one that isn't overly complex. Unfortunately I have never tried my hand at jpeg before so I wouldn't know the "best" jpeg sources.
    Last edited by Lucas; 10th August 2015 at 05:43.

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    Quote Originally Posted by pk-compression View Post
    What do you suggest is the best way to implement these ideas and compare them to the performance of existing standard implementations? Matlab, Octave, or C? I did look up the libjpeg implementation in C.
    I would always suggest to use a real programming language. Simplifying in Matlab or Octave is tempting, but you often miss the gory details. "libjpeg" is not a JPEG-authorized reference, and I would not recommend it. It implements compression modes that are not JPEG, and it does not implement JPEG fully either.

    Quote Originally Posted by pk-compression View Post
    Should I take any existing open source implementation of JPEG and then modify that code to add my own ideas? Or is it better to implement the code myself in Matlab or Octave? I have already been playing around in Octave code to statistically analyse test images w.r.t my ideas.
    As said, if you want working code that allows compression *and* decompression, and you want to verify that things really work, I would very much recommend to get your hands dirty and start with a C code.

    You'll find a JPEG implementation on www.jpeg.org, specifically at the JPEG XT section (not kidding!) that supports JPEG fully. Go for the GPL code for full JPEG support. (JPEG XT is a forwards and backwards extension of JPEG, but you only need JPEG XT part 1 aka "JPEG as we know it").

    You'll also find a couple of additional options to improve coding performance in this code there, specifically deadzone quantization and the ability to choose alternative quantization matrices.

    If you want to test further options, go to http://jpegonline.rus.uni-stuttgart.de/ where you can test additional options such as the de-ringer and the trellis-quantizer.

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