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Bug 578729 - gimp-free-select drops pixel from middle of single pixel line
gimp-free-select drops pixel from middle of single pixel line
Status: RESOLVED NOTABUG
Product: GIMP
Classification: Other
Component: Script-Fu
2.6.6
Other All
: Normal minor
: ---
Assigned To: GIMP Bugs
GIMP Bugs
Depends on:
Blocks:
 
 
Reported: 2009-04-11 22:51 UTC by Charles Belov
Modified: 2009-07-14 07:42 UTC
See Also:
GNOME target: ---
GNOME version: ---


Attachments
Script-Fu demonstrating the bug (2.14 KB, application/octet-stream)
2009-04-11 22:52 UTC, Charles Belov
Details
Script-Fu demonstrating the work-around (2.14 KB, application/octet-stream)
2009-04-11 22:53 UTC, Charles Belov
Details

Description Charles Belov 2009-04-11 22:51:55 UTC
Please describe the problem:
A GIMP free select leaves a gap in the middle for certain coordinates.

Steps to reproduce:
1. Install script diagonal-select4a.scm in your Script-Fu path. 
2. Run script  "Test diagonal gradient with 4 points (alternative)" from (new) Debug menu.
3. Select > None



Actual results:
A diagonal single-pixel line is drawn. The pixel at X 49 Y 49 is white.

Expected results:
A diagonal single-pixel line is drawn. The pixel at X 49 Y 49 is black.

Does this happen every time?
Yes.

Other information:
1. Install script diagonal-select4b.scm in your Script-Fu path. 
2. Run script  "Test diagonal gradient with 4 points (alternative B)" from (new) Debug menu.
3. Select > None

Result: A diagonal single-pixel line is drawn. The pixel at X 49 Y 49 is black.

So there is a work-around.  The only functional difference is that the coordinates for the line draw the line 1 pixel further off the image in the b version than in the a version.
Comment 1 Charles Belov 2009-04-11 22:52:49 UTC
Created attachment 132531 [details]
Script-Fu demonstrating the bug
Comment 2 Charles Belov 2009-04-11 22:53:17 UTC
Created attachment 132532 [details]
Script-Fu demonstrating the work-around
Comment 3 Massimo 2009-07-11 10:07:53 UTC
These scripts pass a self intersecting polygon to 
gimp-free-select to create a selection.

The difference is that in one case the intersection is 
exactly at the center of a pixel (thus not part of  
the selection), whereas in the other is at the corner 
of four pixels (two of which are inside and two outside
of the selection).

For me this is not a bug.