Search found 5 matches

by xooyoozoo
2013-02-28T23:25:25-07:00
Forum: Digital Image Processing
Topic: JPEG q-tables, 'quality', and some other image formats
Replies: 12
Views: 30519

Re: JPEG q-tables, 'quality', and some other image formats

Edit : Well, I guess I missed the obvious fact that Photoshop automatically uses different quality factors for luma and chroma, and structural similarity completely focuses on luma. Have you tried to convert images to monochrome before compression? convert orginal.png -fx luminance grayscale.png I ...
by xooyoozoo
2013-02-25T17:09:18-07:00
Forum: Digital Image Processing
Topic: JPEG q-tables, 'quality', and some other image formats
Replies: 12
Views: 30519

Re: JPEG q-tables, 'quality', and some other image formats

Are these simple settings for IM "enough" for optimizing Jasper JP2K image quality? convert $f -define jp2:rate=$i $g.jp2 Because I got some terrible results... here's Kodak 24 JPEG vs Jasper at ~35KB: http://imgur.com/a/3ayPz#0 . Kodak 21 and 3 JP2K encoders . And here's some quantitative analysis ...
by xooyoozoo
2013-02-24T16:40:43-07:00
Forum: Digital Image Processing
Topic: JPEG q-tables, 'quality', and some other image formats
Replies: 12
Views: 30519

Re: JPEG q-tables, 'quality', and some other image formats

To that end, I whipped up a small comparison using a state-of-the-art perceptual metric, IW-SSIM What program you used for this comparison? This interest me, because it could help in the development of better quantization tables. Just plain old Matlab. There are numerous C/C++ implementations of SS...
by xooyoozoo
2013-02-24T16:20:30-07:00
Forum: Digital Image Processing
Topic: JPEG q-tables, 'quality', and some other image formats
Replies: 12
Views: 30519

Re: JPEG q-tables, 'quality', and some other image formats

As there seems to be some interest here, I'll copy-paste a post I just made on the Doom9 forums: ---------- The problem with graphs in the first post is that the data they present is too discrete. Aggregation makes for much better visualization and generalization. To that end, we're going to take th...
by xooyoozoo
2013-02-17T18:41:31-07:00
Forum: Digital Image Processing
Topic: JPEG q-tables, 'quality', and some other image formats
Replies: 12
Views: 30519

JPEG q-tables, 'quality', and some other image formats

Edit : Redid these tests, except I fixed WebP parameters and used lossless sources. In hindsight, this subject might not pertain to ImageMagick very much, so I posted it on the Doom9 forums . Edit #2 : I posted the gist below. After observing Photoshop's "Save for Web" JPEG performance and comparin...