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Bug 72876 - Incorrect RGBA resampling in Map Object plug-in
Incorrect RGBA resampling in Map Object plug-in
Status: RESOLVED FIXED
Product: GIMP
Classification: Other
Component: Plugins
1.x
Other All
: Normal normal
: ---
Assigned To: GIMP Bugs
Daniel Egger
Depends on: 105577
Blocks: 70335
 
 
Reported: 2002-02-27 17:36 UTC by Raphaël Quinet
Modified: 2005-01-01 21:56 UTC
See Also:
GNOME target: ---
GNOME version: ---


Description Raphaël Quinet 2002-02-27 17:36:07 UTC 
If two pixels have different opacity values (alpha channel), then their
colors are not averaged correctly by the Map->Map Object plug-in.  The
problem is already visible in the preview window.

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 Yeti 2003-02-08 13:06:03 UTC 
The solution depends on how bug #105577 will be resolved, because most
of the problems are buried in gimp_bilinear_rgba ().
Comment 2 Sven Neumann 2003-02-18 17:53:49 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.