MozJPEG – Mozilla JPEG Encoder Project

MozJPEG improves JPEG compression efficiency achieving higher visual quality and smaller file sizes at the same time. It is compatible the JPEG standard, and the vast majority of the world’s deployed JPEG decoders.

MozJPEG is a patch for libjpeg-turbo. MozJPEG is binary-compatible with both libjpeg-turbo and the classic libjpeg. This makes it possible to use MozJPEG as a drop-in replacement for libjpeg, and even install it as a system-wide replacement.

This is free and open source software.

Features include:

  • Progressive encoding with “jpegrescan” optimization. It can be applied to any JPEG file (with jpegtran) to losslessly reduce file size. Parameters of progressive JPEG passes influence compression, so it’s possible to make smaller files by tuning them.
  • Trellis quantization. When converting other formats to JPEG it maximizes quality/filesize ratio. Simple JPEG encoders discard a fixed amount of detail according to quality set, but MozJPEG looks how many bits it would cost to write each detail and discards details that compress the least. This makes files much smaller, but also tends to make images look softer (which, depending on an image, may be a good or a bad thing).
  • Cleaner black-on-white text and lines.
  • Smoother high-DPI “compressive” images.
  • Comes with new quantization table presets, e.g. tuned for high-resolution displays.
  • Fully compatible with all web browsers.
  • Can be seamlessly integrated into any program that uses the industry-standard libjpeg API. There’s no need to write any MozJPEG-specific integration code.

Website: github.com/mozilla/mozjpeg
Support: Photo Compression
Developer: Mozilla (MozJJPEG is a patch for libjpeg-turbo)
License: Custom BSD-like licenses

MozJPEG is written in C and Assembly. Learn C with our recommended free books and free tutorials. Learn Assembly with our recommended free books and free tutorials.

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