On Mon, 18 Feb 2019 21:50:08 +0100, Sturm Flut wrote: > Dear Robert, > > Am 18.02.19 um 17:54 schrieb Robert Krawitz: > >>> the comment holds some validity in this particular case since darktable >>> can't losslessly crop a JPEG file, but other tools can. If the original >>> poster ended up just cropping (and not rotating) most files, something >>> like cropgui[1] would actually yield better image quality. >> >> Well, that's interesting to know. Unfortunately, cropgui isn't quite >> right either; it doesn't do rotation. > > Yeah, lossless rotation is only possible in 90 degree steps with > JPEGs. jpegtran (the tool working in the background of cropgui) > exploits a special property of the JPEG compression scheme. This > property makes it possible to discard parts of the image data > without having to re-encode the rest. There are certain limitations > to this trick (you can't cut at every pixel coordinate, but only at > the bounds of slightly larger blocks). > > But if all you have is a JPEG, you only want to cut it, and image > quality is a concern, then jpegtran/cropgui would be a better option > than most generic image editing tools.
Absolute image quality isn't my concern; I'm shooting basketball mostly at ISO 6400 (I do export them at a high quality setting). And I do rotate some photos if the camera's rolled badly, which is not uncommon. And cropgui has exactly the same UI problem as Darktable -- you have to crop from the edges rather than just drawing the bounding box in one motion. It's also slow, since it exports the photos on the fly, and doesn't leave a sidecar for me to record what crop I did. If I can reverse engineer RawTherapee's settings, I'll probably do the actual conversions via a shell/perl script using convert to do the fun stuff if it's fast enough. -- Robert Krawitz <[email protected]> *** MIT Engineers A Proud Tradition http://mitathletics.com *** Member of the League for Programming Freedom -- http://ProgFree.org Project lead for Gutenprint -- http://gimp-print.sourceforge.net "Linux doesn't dictate how I work, I dictate how Linux works." --Eric Crampton ___________________________________________________________________________ darktable developer mailing list to unsubscribe send a mail to [email protected]
