GNOME Bugzilla – Bug 162493
jpeg renders incorrectly
Last modified: 2005-01-05 17:14:35 UTC
If I load an image, http://xerxes.kvz.tudelft.nl/pic/f1.jpg, I see incorrectly rendered bands (vertically). In gtksee I do not have this problem. Maybe this is a libjpeg (or whatever) problem.
If you view the image at 100% zoom, the bands are not there. I believe they are caused by an interaction between the way that GIMP zooms (by simply deleting a fraction of columns from the display), and a periodicity in the pixel-noise of your image, possibly caused by jpeg artifact. (This is known in the trade as "aliasing".) Anyway, the fact that the bands are not visible at 100% zoom means that they only affect the display, not the underlying image data, so you can safely ignore them. The zooming in GIMP is well known to be imperfect -- we live with it because a better-quality zoom would quite substantially slow down the display for large images like yours. I am going to resolve this as WONTFIX because, while we recognize that the program is imperfect, the artifacts you are seeing are a deliberate tradeoff for the speed that the display method gives. (Note: in this response, I assumed that the bands I see are the same as the bands that you see. If you think they are more severe than I make them sound, please attach a screenshot illustrating what happens on your screen.) (Another note: GIMP 2.0.6 is no longer actively supported. If there were any fix, it would appear in GIMP 2.2.)
> My "BIG" problem with a WONTFIX is, is that I cannot view/evaluate the > picture (even if I want to wait for it). My > girlfriend-photographer/painter has a problem with that. This is > supposed to be a graphics program, and it cannot show a picture > without huge deformations (zooming is not an option with big > pictures...). The whole purpose of the picture was to show the > different structures of the materials in the picture. Working/changing > that picture is now impossible because she cannot see the effect > properly. A screenshot of this is located at http://xerxes.kvz.tudelft.nl/pic/f1_with_bands.bmp
Okay, I should in any case have resolved this differently -- it is actually a duplicate of a long-standing request. But if I may make a suggestion for a temporary workaround-- the problem is being caused by the fact that the image is very grainy at the pixel level, and the grain has a regular statistical structure. If you simply run one repetition of the "Blur" filter to smooth out the grain a bit, then all the visible banding disappears, and you don't lose any meaningful resolution -- unless graininess is what you actually want.
*** This bug has been marked as a duplicate of 76096 ***