tag:blogger.com,1999:blog-7844549485270153160.post291802843828522425..comments2024-02-14T00:37:51.623-08:00Comments on My Blog: JPEG quality is a meaningless numberAlexander E. Patrakovhttp://www.blogger.com/profile/15370096336423115833noreply@blogger.comBlogger3125tag:blogger.com,1999:blog-7844549485270153160.post-13139143767581764762015-12-02T02:03:07.730-08:002015-12-02T02:03:07.730-08:00I know this post is old, but incase someone stumbl...I know this post is old, but incase someone stumbles upon it https://blogs.gnome.org/raphael/2007/10/23/mapping-jpeg-compression-levels-between-adobe-photoshop-and-gimp-24/ gives a good guide to PS vs Gimp jpeg compression.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-7844549485270153160.post-71823926066189028342008-12-13T22:29:00.000-08:002008-12-13T22:29:00.000-08:00First, libjpeg does not do any quality detection. ...First, libjpeg does not do any quality detection. Software that "detects" quality actually gathers some statistics on the quantization tables and matches the results against known values. See, e.g., <A HREF="http://trac.imagemagick.org/browser/ImageMagick/branches/ImageMagick-6.4.7/coders/jpeg.c#L871" REL="nofollow">this code from ImageMagick</A>, although it contains protection against quantization tables not created by libjpeg.<BR/><BR/>But anyway, the resulting file size (47 KB) and the quantization tables made by libjpeg at 85% are close to the same characteristics of the file made with Photoshop at 60% quality.Alexander E. Patrakovhttps://www.blogger.com/profile/15370096336423115833noreply@blogger.comtag:blogger.com,1999:blog-7844549485270153160.post-59865410325243442682008-12-13T15:05:00.000-08:002008-12-13T15:05:00.000-08:00what qulity detect libjpg if open photoshop image?...what qulity detect libjpg if open photoshop image?Anonymousnoreply@blogger.com