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[Bug 10799] drawImage/pattern filters underspecified

From: <bugzilla@jessica.w3.org>
Date: Tue, 07 Dec 2010 17:25:18 +0000
To: public-html-bugzilla@w3.org
Message-Id: <E1PQ1Hy-0007Bc-VL@jessica.w3.org>
http://www.w3.org/Bugs/Public/show_bug.cgi?id=10799

Philip Taylor <excors@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|excors@gmail.com            |ian@hixie.ch

--- Comment #11 from Philip Taylor <excors@gmail.com> 2010-12-07 17:25:18 UTC ---
(Sorry, been a bit distracted and didn't get around to this earlier.)

I think this should do what I suggested (though if this text is adopted I make
no guarantees that I will not file further bugs saying it's all wrong):

For drawImage:

Remove the text "Pixels of the source rectangle that are not entirely within
the source image must be treated as transparent black."

Somewhere in this section, add the text:

"""
If the original image data is a bitmap image, the value painted at a point in
the destination rectangle is computed by filtering the original image data. The
user agent may use any filtering algorithm (for example bilinear interpolation
or nearest-neighbor). When the filtering algorithm requires a pixel value from
outside the original image data, it must instead use the value from the nearest
edge pixel. (That is, the filter uses 'clamp-to-edge' behavior.)
"""

For createPattern, add the text:

"""
If the original image data is a bitmap image, the value painted at a point in
the area of the repetitions is computed by filtering the original image data.
The user agent may use any filtering algorithm (for example bilinear
interpolation or nearest-neighbor). When the filtering algorithm requires a
pixel value from outside the original image data, it must instead use the value
from wrapping the pixel's coordinates to the original image's dimensions. (That
is, the filter uses 'repeat' behavior, regardless of the value of
<var>repetition</var>.)
"""

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Received on Tuesday, 7 December 2010 17:25:21 UTC

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