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Bug 105496 - Incorrect RGBA resampling in Lighting Effects plug-in
Incorrect RGBA resampling in Lighting Effects plug-in
Status: RESOLVED FIXED
Product: GIMP
Classification: Other
Component: Plugins
git master
Other Linux
: Normal normal
: ---
Assigned To: GIMP Bugs
Daniel Egger
Depends on: 105577
Blocks: 70335
 
 
Reported: 2003-02-07 15:47 UTC by Yeti
Modified: 2004-12-22 21:47 UTC
See Also:
GNOME target: ---
GNOME version: ---



Description Yeti 2003-02-07 15:47:17 UTC
If two pixels have different opacity values (alpha channel), then their
colors are not averaged correctly by the Lighting Effects plug-in.
It looks like the RGB channels are resampled without taking the opacity
into account.  As a result, the (invisible) color of a transparent pixel
can bleed into an opaque pixel.  The resulting image is incorrect.

See bug #70335 for some test images and a longer description of the
problem.  This problem affects many other tools and plug-ins.
Comment 1 Raphaël Quinet 2003-02-07 16:01:08 UTC
Easily confirmed with 1.2.4-pre2, using the default settings in the
plug-in with the image test2.xcf.gz that I supplied in bug #70335.

The interesting thing is that the preview seems to work correctly, but
the final result is wrong.  Also, the result is different if you check
"create new image" or not.  This difference seems to suggest that the
plug-in does not deal with transparency correcly - not only when
averaging pixels, but also when creating a new image.  It looks like
we have more than one bug here...
Comment 2 Yeti 2003-02-08 13:04:08 UTC
The solution depends on how bug #105577 will be resolved, because most
of the problems are burried in gimp_bilinear_rgba ().
Comment 3 Sven Neumann 2003-02-18 17:53:30 UTC
2003-02-18  Sven Neumann  <sven@gimp.org>

	Applied patches from David Necas <yeti@physics.muni.cz> that fix
	incorrect RGBA resampling in a number of plug-ins:

	* libgimpcolor/gimpbilinear.c (gimp_bilinear_rgba): fixes RGBA
	resampling in Map Object and Lighting Effects plug-ins (#72876 and
	#105496).

	* plug-ins/common/curve_bend.c: fixes bug #72863.
	* plug-ins/common/deinterlace.c: fixes bug #72856.
	* plug-ins/common/gauss_iir.c: fixes bug #72848.
	* plug-ins/common/gauss_rle.c: fixes bug #72849.
	* plug-ins/common/iwarp.c: fixes bug #72865 (except preview, see
	comment).
	* plug-ins/common/mblur.c: fixes bug #72850.
	* plug-ins/common/pixelize.c: fixes bug #72851.
	* plug-ins/common/polar.c: fixes bug #72866.
	* plug-ins/common/ripple.c: fixes bug #72868.