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Bug 72875 - Incorrect RGBA resampling in Make Seamless plug-in
Incorrect RGBA resampling in Make Seamless 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:
Blocks: 70335
 
 
Reported: 2002-02-27 17:34 UTC by Raphaël Quinet
Modified: 2005-01-01 21:56 UTC
See Also:
GNOME target: ---
GNOME version: ---

Attachments
Proposed patch (4.82 KB, patch)
2003-03-02 13:36 UTC, Yeti 		none Details | Review
Source image (111 bytes, image/png)
2003-03-02 13:48 UTC, Yeti 		  Details
Old weighting function (1.95 KB, image/png)
2003-03-02 13:48 UTC, Yeti 		  Details
New weighting function (2.04 KB, image/png)
2003-03-02 13:49 UTC, Yeti 		  Details

Description Raphaël Quinet 2002-02-27 17:34:55 UTC 
If two pixels have different opacity values (alpha channel), then their
colors are not averaged correctly by the Map->Make Seamless 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 Yeti 2003-03-02 13:36:12 UTC 
Created attachment 14726 [details] [review]
Proposed patch
Comment 2 Yeti 2003-03-02 13:47:24 UTC 
Attached a patch against 1.3.12.

Unfortunately I'm too honest to conceal I changed the weighting
function slightly, too.  To better, I hope.  It was in the TODO since
1997 :o)  I'm attaching images visualizating the weighting functions.
Comment 3 Yeti 2003-03-02 13:48:13 UTC 
Created attachment 14727 [details]
Source image
Comment 4 Yeti 2003-03-02 13:48:57 UTC 
Created attachment 14728 [details]
Old weighting function
Comment 5 Yeti 2003-03-02 13:49:50 UTC 
Created attachment 14729 [details]
New weighting function
Comment 6 Sven Neumann 2003-03-17 11:20:13 UTC 
2003-03-17  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:

	* plug-ins/common/fractaltrace.c: fixes bug #72873.
	* plug-ins/common/tiler.c: fixes bug #72875.
	* plug-ins/common/waves.c: fixes bug #72870.
	* plug-ins/common/whirlpinch.c: fixes bug #72871.