[Mono-bugs] [Bug 76310][Maj] New - Cairo with no antialising does not respect line widths

bugzilla-daemon at bugzilla.ximian.com bugzilla-daemon at bugzilla.ximian.com
Sat Oct 1 10:15:46 EDT 2005

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Changed by jordi at ximian.com.


--- shadow/76310	2005-10-01 10:15:46.000000000 -0400
+++ shadow/76310.tmp.9658	2005-10-01 10:15:46.000000000 -0400
@@ -0,0 +1,36 @@
+Bug#: 76310
+Product: Mono: Class Libraries
+Version: 1.0
+OS Details: 
+Status: NEW   
+Priority: Major
+Component: libgdiplus
+AssignedTo: jordi at ximian.com                            
+ReportedBy: jordi at ximian.com               
+QAContact: mono-bugs at ximian.com
+TargetMilestone: ---
+Summary: Cairo with no antialising does not respect line widths
+After turning antialiasing off in Cairo 1.00 DrawLine and
+other functions basic drawing functions start to work different that
+expected. With antialiasing off in Cairo lines that are supposed to be a
+single pixel width have various variations in width. 
+This a well-know and documented issue. John Hobby did his PhD on the
+solution to this problem. There is a shorten version of PhD findings on
+the web:
+[Hobby89] John D. Hobby, Rasterizing Curves of Constant Width, JACM
+36(2), 1989.
+In order to fix this problem the best solution is to implement an
+algorithm to generate Hobby's "Pen polygons". These respect the desired
+width and will make us to look right when AA is off. According to Cairo
+hacker's, a hack in cairo-pen.c:_cairo_pen_init with Hobby's algorithm
+will fix the problem.

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