Bug 96581

Summary: [Cairo] canvas drawImage with non integer parameters result in transparent pixels.
Product: WebKit Reporter: arno. <a.renevier>
Component: PlatformAssignee: Nobody <webkit-unassigned>
Status: RESOLVED INVALID    
Severity: Normal CC: igor.oliveira, mrobinson
Priority: P2    
Version: 528+ (Nightly build)   
Hardware: Unspecified   
OS: Unspecified   
URL: http://renevier.net/misc/webkit_96581.html
Attachments:
Description Flags
cairo minimal program that reproduce the problematic behaviour none

arno.
Reported 2012-09-12 17:26:41 PDT
Hi, when drawing an image on a canvas with non integer dx or dy parameters, we can observe that some pixels on the border on the drawn image have become transparent. For example, when drawing a black image on a red canvas with a white background, we can observe, a white border around the image.
Attachments
cairo minimal program that reproduce the problematic behaviour (2.37 KB, text/x-csrc)
2012-09-12 17:32 PDT, arno. 		no flags
Details
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arno.
Comment 1 2012-09-12 17:31:45 PDT
Here is a cairo program which kind of reproduce the behaviour in webkit cairo backend. An image is drawn on another. If the translation has non integer numbers, some pixel become semi transparents. I don't known if that's a bug in cairo or intended behaviour
arno.
Comment 2 2012-09-12 17:32:51 PDT
Created attachment 163743 [details] cairo minimal program that reproduce the problematic behaviour
arno.
Comment 3 2012-09-13 10:53:49 PDT
The behaviour seems to have change in cairo 1.11.4 (http://cgit.freedesktop.org/cairo/commit/?id=a80bf9ed43ebb510027f95f623a012c55f7566b3) The example url does not have transparent pixels with recent cairo
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