Bug 2488

Summary:	Rotating image 180� offsets it by 1 pixel
Product:	cairo	Reporter:	Kristian Høgsberg <krh>
Component:	image backend	Assignee:	Carl Worth <cworth>
Status:	RESOLVED FIXED	QA Contact:	cairo-bugs mailing list <cairo-bugs>
Severity:	normal
Priority:	high	CC:	benjamin, bertram.felgenhauer, jwatt
Version:	0.9.3
Hardware:	All
OS:	All
Whiteboard:
i915 platform:		i915 features:
Attachments:	PNG showing the problem C code to generate the PNG proposed pix for the problem Similar patch for fb in xserver

Description Kristian Høgsberg 2005-02-07 09:02:31 UTC

See attached PNG.  The image surface consisting of the red square and the black
outline is rotated 180° and composited onto the target surface.  The black
outline marks the edge of the image.  The yellow square marks the area where the
black outline should be, but as can be seen from the PNG the black square is
offset 1 pixel down and to the right.  Part of the black outline is clipped
because of this.

Comment 1 Kristian Høgsberg 2005-02-07 09:03:27 UTC

Created attachment 1848 [details]
PNG showing the problem

Comment 2 Kristian Høgsberg 2005-02-07 09:03:59 UTC

Created attachment 1849 [details]
C code to generate the PNG

Comment 3 James Henstridge 2005-07-01 00:44:54 UTC

Are you sure you are rotating around the right axis? (i.e. not half a pixel out
in the X and Y direction?)

Comment 4 Carl Worth 2005-08-22 17:14:21 UTC

Move bugs against "cvs" version to "0.9.3" so we can remove the "cvs" version.

Comment 5 Bertram Felgenhauer 2005-09-16 10:56:35 UTC

Created attachment 3296 [details] [review]
proposed pix for the problem

See also:
http://lists.freedesktop.org/archives/cairo/2005-September/005285.html

[pixman] Changelog:

2005-09-16  Bertram Felgenhauer  <int-e@gmx.de>

	Bug #2488

	* src/fbcompose.c (fbFetchSourcePict, fbFetchTransformed): use the
	center of the pixel as the sampling point for rendering.

	* src/fbcompose.c (fbFetchTransformed): give source image values
	maximim effect in the center of the corresponding pixel.

Comment 6 Kristian Høgsberg 2006-06-13 17:14:18 UTC

Patch comitted and test cases updated.  Thanks.

Comment 7 Kristian Høgsberg 2006-06-13 22:15:56 UTC

Link to git commit:

http://gitweb.freedesktop.org/?p=cairo;a=commit;h=b104a79502e2c01c508e40d83613ecfa001a2a4e

Comment 8 Kristian Høgsberg 2006-06-16 15:29:35 UTC

Created attachment 5946 [details] [review]
Similar patch for fb in xserver

The bug is also present in the x server, attached patch is a port of the pixman
patch to fb.

Use of freedesktop.org services, including Bugzilla, is subject to our Code of Conduct. How we collect and use information is described in our Privacy Policy.