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html5/spec Overview.html,1.2378,1.2379

From: Ian Hickson via cvs-syncmail <cvsmail@w3.org>
Date: Fri, 12 Jun 2009 18:44:57 +0000
To: public-html-commits@w3.org
Message-Id: <E1MFBkH-0001Ji-82@lionel-hutz.w3.org>
Update of /sources/public/html5/spec
In directory hutz:/tmp/cvs-serv5044

Modified Files:
	Overview.html 
Log Message:
Mention that getImageData() might return different pixel data than you set, due to premultiplying. (whatwg r3230)

Index: Overview.html
===================================================================
RCS file: /sources/public/html5/spec/Overview.html,v
retrieving revision 1.2378
retrieving revision 1.2379
diff -u -d -r1.2378 -r1.2379
--- Overview.html	12 Jun 2009 07:49:58 -0000	1.2378
+++ Overview.html	12 Jun 2009 18:44:54 -0000	1.2379
@@ -22606,6 +22606,12 @@
   for all of the <code title="dom-context-2d-getImageData"><a href="#dom-context-2d-getimagedata">createImageData()</a></code>, <code title="dom-context-2d-getImageData"><a href="#dom-context-2d-getimagedata">getImageData()</a></code> and <code title="dom-context-2d-putImageData"><a href="#dom-context-2d-putimagedata">putImageData()</a></code>
   operations.</p>
 
+  <p class="note">Due to the lossy nature of converting to and from
+  premultiplied alpha color values, pixels that have just been set
+  using <code title="dom-context-2d-putImageData"><a href="#dom-context-2d-putimagedata">putImageData()</a></code> might be
+  returned to an equivalent <code title="dom-context-2d-getImageData"><a href="#dom-context-2d-getimagedata">getImageData()</a></code> as
+  different values.</p>
+
   <p>The current path, <a href="#transformations" title="dom-context-2d-transformation">transformation matrix</a>,
   <a href="#shadows" title="shadows">shadow attributes</a>, <a href="#dom-context-2d-globalalpha" title="dom-context-2d-globalAlpha">global alpha</a>, the <a href="#clipping-region" title="clipping region">clipping region</a>, and <a href="#dom-context-2d-globalcompositeoperation" title="dom-context-2d-globalCompositeOperation">global composition
   operator</a> must not affect the <code title="dom-context-2d-getImageData"><a href="#dom-context-2d-getimagedata">getImageData()</a></code> and <code title="dom-context-2d-putImageData"><a href="#dom-context-2d-putimagedata">putImageData()</a></code>
Received on Friday, 12 June 2009 18:45:04 GMT

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