Hacker News Reader

Comment by notlisted | Hacker News Reader

How does this MozJPEG 2.0 encoding compare to JPEGMini? I've been using JPEGMini for all client projects, it results in optimized JPEGs that work on all platforms with minute differences, rarely visible to the naked eye, only when I subtract pre/post in Photoshop. Very rarely does it save less than 5% and for larger images (saved with PhotoShop, save for web) often 15-30% or even more.

Is the test set of images available?

View on HN

jpegmini works by compressing an image as much as possible while keeping the distortion calculated by there particular metric below a threshold. To compare against mozjpeg you'd need to compress a bunch of images with JPEGMini and then compress those images with mozjpeg so that they were the same size. You could then compare the quality of the resulting images.

The test set of images is here: https://github.com/bdaehlie/web_image_formats/tree/master/im...

If you're interested, https://github.com/dwbuiten/smallfry is program similar to JPEGMini that uses mozjpeg as its backend.

How much extra saving does JPEGMini or smallfry offer over a sanely but conservatively encoded JPEG?

http://people.mozilla.org/~josh/lossy_compressed_image_study...

mozjpeg does Trellis quantization, there is no detailed explanation about jpegmini, a guess is it optimizes the DCT similarly to how it is described in this paper:

http://vision.arc.nasa.gov/publications/sid93/sid93.pdf

There are some papers by the JPEGMini people that give a pretty good hint as to how it works:

http://spie.org/Publications/Proceedings/Paper/10.1117/12.87... http://spie.org/Publications/Proceedings/Paper/10.1117/12.87...

jpegrescan AFAIK is the gold standard today. https://github.com/kud/jpegrescan

Reply on news.ycombinator.com