// Patrick Louis

MozJpeg Correlation

Hello fellow readers,

I’ve wanted to try mozjpeg since it came out. After getting it installed I was surprised by how awesome the compression is.

To get a bit of an idea of mozjpeg, it is a fork of the libjpeg. When installed, it replaces the original cjpeg with theirs (works only on Unix). Here’s a nice introduction to it.

The redundant questions are:

  • What would be the best compression ratio to use?
  • Should I use progressive JPEG or non-progressive, what’s the difference?

The second one is an easy guess. Progressive JPEG gives a smaller output but it’ll render in subsequent scan, from low quality to high quality. I personally find this extremely annoying when used on the web.

And thus, I’ve started a mini-project to gather statistics on the first question. I’ve hacked around a script that’ll open 2 images, one being the original, the other a compressed one, and then asks if the compression is satisfying. It re-iterates and compress the next image with a higher ratio until the user is unsatisfied. At this point it stores the last best compression used and also keeps the last best image.

I’m hoping that after gathering a lot of inputs the program will be able to guess, if there’s a correlation between the size of the image and the compression ratio, what compression is best to use.

Here’s the link to the project on Github.


If you want to have a more in depth discussion I'm always available by email or irc. We can discuss and argue about what you like and dislike, about new ideas to consider, opinions, etc..
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