Nition is correct, I think. As far as I can tell, 'raw pixels' is not quite accurate. Both PackJPG and Lepton seem to decompress as far as frequency-domain coe

Nition is correct, I think. As far as I can tell, 'raw pixels' is not quite accurate. Both PackJPG and Lepton seem to decompress as far as frequency-domain coefficients, but no further. That means they don't repeat the lossy stages in JPEG encoding - the transformation of pixel data to the frequency domain, and the discarding of high frequency infomation. It looks like PackJPG and Lepton do some interesting tricks with the coefficients to essentially make them more amenable to the following lossless compression. Both PackJPG and Lepton have their own file format, so they're definitely not outputting standard JPEG images. Here's the Lepton page: https://blogs.dropbox.com/tech/2016/07/lepton-image-compression-saving-22-losslessly-from-images-at-15mbs/ https://blogs.dropbox.com/tech/2016/07/lepton-image-compress... And for more detail, here's the paper that PackJPG is based on: http://www.elektronik.htw-aalen.de/packjpg/_notes/PCS2007_PJPG_paper_final.pdf http://www.elektronik.htw-aalen.de/packjpg/_notes/PCS2007_PJ...