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dropbox / lepton

Lepton is a tool and file format for losslessly compressing JPEGs by an average of 22%.
https://blogs.dropbox.com/tech/2016/07/lepton-image-compression-saving-22-losslessly-from-images-at-15mbs/
Apache License 2.0
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why not compress the residulals of ac coefficients and predicted values? #106

Open aaaaeerr opened 6 years ago

aaaaeerr commented 6 years ago

can we improve compression rate by compress the residulals of ac coefficients and its predicted values?

danielrh commented 6 years ago

possibly! I haven't had luck doing so in the past, but it might be worth trying... The place where there is likely to be the biggest improvement would be in the edge coefficients... the math there must be off by a bit or something, because simply subtracting the prediction from the result yields significantly worse compression

xiaoxiongli commented 4 years ago

Dear @aaaaeerr, how about your result?