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2004[Opera] How to handle transparent images for toDataURL(). Just allow the UA to premultiply the alpha and output that whie dropping the alpha channel, instead of worrying about the background color or whatnot. It's up to authors to make the background color non-transparent.2008-08-05 09:57
@@ -17995,20 +17995,25 @@ interface <dfn>CueRangeCallback</dfn> {
   title="">type</var>)</code></dfn> method (when called with one
   <em>or more</em> arguments) must return a <code
   title="">data:</code> URL containing a representation of the image
   in the format given by <var title="">type</var>. The possible values
   are MIME types with no parameters, for example
   <code>image/png</code>, <code>image/jpeg</code>, or even maybe
   <code>image/svg+xml</code> if the implementation actually keeps
   enough information to reliably render an SVG image from the
   canvas.</p>
 
+  <p>For image types that do not support an alpha channel, the image
+  must be composited onto a solid black background using the
+  source-over operator, and the resulting image must be the one used
+  to create the <code title="">data:</code> URL.</p>
+
   <p>Only support for <code>image/png</code> is required. User agents
   may support other types. If the user agent does not support the
   requested type, it must return the image using the PNG format.</p>
 
   <p>User agents must convert the provided type to lower case before
   establishing if they support that type and before creating the <code
   title="">data:</code> URL.</p> <!-- XXX define "convert to lower
   case" -->
 
   <p class="note">When trying to use types other than

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