Bug 16847

Summary: Allow to restrict filter to source picture only
Product: xorg Reporter: Clemens Eisserer <linuxhippy>
Component: Lib/XrenderAssignee: Xorg Project Team <xorg-team>
Status: RESOLVED INVALID QA Contact: Xorg Project Team <xorg-team>
Severity: normal    
Priority: medium    
Version: git   
Hardware: Other   
OS: All   
Whiteboard:
i915 platform: i915 features:
Attachments:
Description Flags
Image which illustrates the bleeding
none
small program which illustrates the problem none

Description Clemens Eisserer 2008-07-25 06:04:21 UTC 
Created attachment 17888 [details]
Image which illustrates the bleeding

The billinear (or better) filters provided by XRender currently interpolate pixels which are on the source-border with transparent (when RepeatNone is set).
This results for large scale factors in serioud bleeding.
The image attached is a 2x2 image, scaled with 100/10.

Therefor its not possible to Composite with billinear interpolation without blurry edges.
Cairo-1.6.4 introduced support for RepeatPad on image-surfaces (not supported on x-surfaces):
> This mode allows applications to use `cairo_rectangle` and
> `cairo_fill` to draw scaled images with high-quality bilinear filtering
> for the internal of the image, but without any objectionably blurry
> edges, (as would happen with the default `EXTEND_NONE` and cairo_paint).

They currently implement RepeatPad, and then filter billinear.
However its often required to just draw a single image rotated, it imposes quite a lot of overhead to generate a mask only to preserve the rotated rectangular geometry the image has.

Would it be possible via XRenderSetPictureFilter's params-field to not interpolate out of the src-bounds?
Comment 1 Clemens Eisserer 2008-07-25 06:05:33 UTC 
Created attachment 17889 [details]
small program which illustrates the problem
Comment 2 Clemens Eisserer 2008-07-31 11:32:14 UTC 
ok, forget about that feature request.
However RepeatPad would be nice.

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