Red Hat Bugzilla – Bug 134970
'jpegtran -rotate 90' can cause image to 'slip'
Last modified: 2007-11-30 17:10:51 EST
Description of problem:
With some images, 'jpegtran -rotate 90' causes the resulting image to
be 'slipped' left by a few pixels, so that what should have been on
the left edge is now in the right edge, and flipped.
For example, like this:
xample, like this:e roF
Version-Release number of selected component (if applicable):
You would not happen to have an example image do demonstrate that,
would you ?
Created attachment 105064 [details]
Sure, here's one. It's already been rotated once, so you can see the effect
already. Rotating it again produces another artifact, again on the right-hand
jpegtran -rotate 90 catmug1.jpg > rotated.jpg
This is documented in the jpegtran man page:
The transpose transformation has no restrictions regarding image
dimensions. The other transformations operate rather oddly if
the image dimensions are not a multiple of the iMCU size
(usually 8 or 16 pixels), because they can only transform complete
blocks of DCT coefficient data in the desired way.
I don't think this is easily fixable short of rewriting the jpeg
transformation support completely, which I'm not up to.