Re: image-dired does not rotate the original image

[Thien-Thi Nguyen]

() "Mathias Dahl" <mathias.dahl@gmail.com>
() Sun, 22 Jul 2007 15:52:16 +0200

   As I mentioned earlier, jpegtran does lossless rotation, something
   `convert' cannot do (or could not the last time I checked).

does this limitation also exist w/ mogrify(1) (or alternatively gm(1)
subcommand mogrify)?  i suppose to check for loss one could use:

 cp foo.jpg foo.orig.jpg
 gm mogrify -rotate -90 foo.jpg
 gm mogrify -rotate  90 foo.jpg
 cmp foo.jpg foo.orig.jpg

however, doing the above (even w/ "-quality 100" for the mogrify commands)
always results in cmp(1) noting a difference, even though visually i could
not tell.  i'm not a graphics format expert; could you suggest a better
way to check for loss?

thi