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html5/spec Overview.html,1.4933,1.4934

From: Ian Hickson via cvs-syncmail <cvsmail@w3.org>
Date: Thu, 12 May 2011 20:40:54 +0000
To: public-html-commits@w3.org
Message-Id: <E1QKcgo-0003dq-7N@lionel-hutz.w3.org>
Update of /sources/public/html5/spec
In directory hutz:/tmp/cvs-serv13977

Modified Files:
	Overview.html 
Log Message:
Attempt to define canvas.toBlob(). (whatwg r6134)

Index: Overview.html
===================================================================
RCS file: /sources/public/html5/spec/Overview.html,v
retrieving revision 1.4933
retrieving revision 1.4934
diff -u -d -r1.4933 -r1.4934
--- Overview.html	12 May 2011 19:10:24 -0000	1.4933
+++ Overview.html	12 May 2011 20:40:49 -0000	1.4934
@@ -27035,6 +27035,8 @@
            attribute unsigned long <a href="#dom-canvas-height" title="dom-canvas-height">height</a>;
 
   DOMString <a href="#dom-canvas-todataurl" title="dom-canvas-toDataURL">toDataURL</a>(in optional DOMString type, in any... args);
+  void <a href="#dom-canvas-toblob" title="dom-canvas-toBlob">toBlob</a>(in <span>FileCallback</span>, in optional DOMString type, in any... args);
+
   object <a href="#dom-canvas-getcontext" title="dom-canvas-getContext">getContext</a>(in DOMString contextId, in any... args);
 };</pre>
    </dd>
@@ -27237,70 +27239,117 @@
     type, and control the way that the image is generated, as given in
     the table below.</p>
 
+    <p>When trying to use types other than "<code>image/png</code>",
+    authors can check if the image was really returned in the
+    requested format by checking to see if the returned string starts
+    with one of the exact strings "<code title="">data:image/png,</code>" or "<code title="">data:image/png;</code>". If it does, the image is PNG,
+    and thus the requested type was not supported. (The one exception
+    to this is if the canvas has either no height or no width, in
+    which case the result might simply be "<code title="">data:,</code>".)</p>
+
    </dd>
 
-   
+   <dt><var title="">canvas</var> . <code title="dom-canvas-toBlob"><a href="#dom-canvas-toblob">toBlob</a></code>(<var title="">callback</var> [, <var title="">type</var>, ... ])</dt>
+
+   <dd>
+
+    <p>Creates a <code><a href="#blob">Blob</a></code> object representing a file
+    containing the image in the canvas, and invokes a callback with a
+    handle to that object.</p>
+
+    <p>The second argument, if provided, controls the type of the
+    image to be returned (e.g. PNG or JPEG). The default is <code title="">image/png</code>; that type is also used if the given
+    type isn't supported. The other arguments are specific to the
+    type, and control the way that the image is generated, as given in
+    the table below.</p>
+
+   </dd>
 
   </dl><div class="impl">
 
   <p>The <dfn id="dom-canvas-todataurl" title="dom-canvas-toDataURL"><code>toDataURL()</code></dfn> method
-  must, when called with no arguments, return a <a href="#data-protocol" title="data
-  protocol"><code title="">data:</code> URL</a> containing a
-  representation of the image as a PNG file. <a href="#refsPNG">[PNG]</a> <a href="#refsRFC2397">[RFC2397]</a></p>
+  must run the following steps:</p>
 
+  <ol><li><p>If the canvas has no pixels (i.e. either its horizontal
+   dimension or its vertical dimension is zero) then return the string
+   "<code title="">data:,</code>" and abort these steps. (This is the
+   shortest <a href="#data-protocol" title="data protocol"><code title="">data:</code>
+   URL</a>; it represents the empty string in a <code title="">text/plain</code> resource.)</li>
 
-  <p>If the canvas has no pixels (i.e. either its horizontal dimension
-  or its vertical dimension is zero) then the method must return the
-  string "<code title="">data:,</code>". (This is the shortest <a href="#data-protocol" title="data protocol"><code title="">data:</code> URL</a>; it
-  represents the empty string in a <code title="">text/plain</code>
-  resource.)</p>
+   <li><p>Let <var title="">file</var> be <a href="#a-serialization-of-the-image-as-a-file">a serialization of the
+   image as a file</a>, using the method's arguments (if any) as
+   the <var title="">arguments</var>.</li>
 
-  <p>When the <code title="dom-canvas-toDataURL"><a href="#dom-canvas-todataurl">toDataURL(<var title="">type</var>)</a></code> method is called with one <em>or
-  more</em> arguments, it must return a <a href="#data-protocol" title="data
-  protocol"><code title="">data:</code> URL</a> containing a
-  representation of the image in the format given by <var title="">type</var>. The possible values are <a href="#mime-type" title="MIME
-  type">MIME types</a> 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>
+   <li><p>Return a <a href="#data-protocol" title="data protocol"><code title="">data:</code> URL</a> representing <var title="">file</var>. <a href="#refsRFC2397">[RFC2397]</a></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 <a href="#data-protocol" title="data protocol"><code title="">data:</code> URL</a>.</p>
+   
+  </ol><p>The <dfn id="dom-canvas-toblob" title="dom-canvas-toBlob"><code>toBlob()</code></dfn> method
+  must run the following steps:</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>
+  <ol><li><p>Let <var title="">callback</var> be the first
+   argument.</li>
+
+   <li><p>Let <var title="">arguments</var> be the second and
+   subsequent arguments to the method, if any.</li>
+
+   <li><p>Let <var title="">file</var> be <a href="#a-serialization-of-the-image-as-a-file">a serialization of the
+   image as a file</a>, using <var title="">arguments</var>.</li>
+
+   <li><p>Return, but continue running these steps
+   asynchronously.</li>
+
+   <li><p>If <var title="">callback</var> is null, abort these
+   steps.</li>
+
+   <li><p><a href="#queue-a-task">Queue a task</a> to invoke the
+   <code>FileCallback</code> <var title="">callback</var> with a
+   <code><a href="#blob">Blob</a></code> object representing <var title="">file</var> as
+   its argument. The <a href="#task-source">task source</a> for this task is the
+   <dfn id="canvas-blob-serialization-task-source">canvas blob serialization task source</dfn>. <a href="#refsFILESYSTEMAPI">[FILESYSTEMAPI]</a> <a href="#refsFILEAPI">[FILEAPI]</a> </li>
+
+  </ol><p>When a user agent is to create <dfn id="a-serialization-of-the-image-as-a-file">a serialization of the image
+  as a file</dfn>, optionally with some given <var title="">arguments</var>, it must create an image file in the format
+  given by the first value of <var title="">arguments</var>, or, if
+  there are no <var title="">arguments</var>, in the PNG format. <a href="#refsPNG">[PNG]</a></p>
+
+  <p>If <var title="">arguments</var> is not empty, the first value
+  must be interpreted as a <a href="#mime-type" title="MIME type">MIME type</a>
+  giving the format to use. If the type has any parameters, it must be
+  treated as not supported.</p>
+
+  <p class="example">For example, the value "<code>image/png</code>" would
+  mean to generate a PNG image, the value "<code>image/jpeg</code>"
+  would mean to generate a JPEG image, and the value
+  "<code>image/svg+xml</code>" would mean to generate an SVG image
+  (which would probably require that the implementation actually keep
+  enough information to reliably render an SVG image from the canvas).</p>
+
+  <p>User agents must support PNG ("<code>image/png</code>"). User
+  agents may support other types. If the user agent does not support
+  the requested type, it must create the file using the PNG format. <a href="#refsPNG">[PNG]</a></p>
 
   <p>User agents must <a href="#converted-to-ascii-lowercase" title="converted to ASCII
   lowercase">convert the provided type to ASCII lowercase</a>
-  before establishing if they support that type and before creating
-  the <a href="#data-protocol" title="data protocol"><code title="">data:</code>
-  URL</a>.</p>
+  before establishing if they support that type.</p>
 
-  </div><p class="note">When trying to use types other than
-  <code>image/png</code>, authors can check if the image was really
-  returned in the requested format by checking to see if the returned
-  string starts with one of the exact strings "<code title="">data:image/png,</code>" or "<code title="">data:image/png;</code>". If it does, the image is PNG, and
-  thus the requested type was not supported. (The one exception to
-  this is if the canvas has either no height or no width, in which
-  case the result might simply be "<code title="">data:,</code>".)<div class="impl">
+  <p>For image types that do not support an alpha channel, the
+  serialized image must be the canvas image composited onto a solid
+  black background using the source-over operator.</p>
 
-  <p>If the method is invoked with the first argument giving a type
-  corresponding to one of the types given in the first column of the
-  following table, and the user agent supports that type, then the
+  <p>If the first argument in <var title="">arguments</var> gives a
+  type corresponding to one of the types given in the first column of
+  the following table, and the user agent supports that type, then the
   subsequent arguments, if any, must be treated as described in the
   second cell of that row.</p>
 
-  </div><table><thead><tr><th> Type <th> Other arguments
-   <tbody><tr><td> image/jpeg
+  </div><table><thead><tr><th> Type <th> Other arguments <th> Reference
+   <tbody><tr><td> <code>image/jpeg</code>
      <td> The second argument<span class="impl">, if it</span> is a
      number in the range 0.0 to 1.0 inclusive<span class="impl">, must
      be</span> treated as the desired quality level. <span class="impl">If it is not a number or is outside that range, the
      user agent must use its default value, as if the argument had
      been omitted.</span>
+     <td> <a href="#refsJPEG">[JPEG]</a>
   </table><div class="impl">
 
   <p>For the purposes of these rules, an argument is considered to be
@@ -27310,11 +27359,10 @@
 
   <p>Other arguments must be ignored and must not cause the user agent
   to raise an exception. A future version of this specification will
-  probably define other parameters to be passed to <code title="dom-canvas-toDataURL"><a href="#dom-canvas-todataurl">toDataURL()</a></code> to allow authors to
-  more carefully control compression settings, image metadata,
-  etc.</p>
+  probably define other parameters to be passed to these methods to
+  allow authors to more carefully control compression settings, image
+  metadata, etc.</p>
 
-  
   </div><div class="impl">
 
   <h5 id="color-spaces-and-color-correction"><span class="secno">4.8.11.1 </span>Color spaces and color correction</h5>
@@ -28651,7 +28699,7 @@
   tables is a common default.)<p>In speech media, table cells can be distinguished by reporting
   the corresponding headers before reading the cell's contents, and by
   allowing users to navigate the table in a grid fashion, rather than
-  serialising the entire contents of the table in source order.<p>Authors are encouraged to use CSS to achieve these effects.<div class="impl">
+  serializing the entire contents of the table in source order.<p>Authors are encouraged to use CSS to achieve these effects.<div class="impl">
   <p>User agents are encouraged to render tables using these
   techniques whenever the page does not use CSS and the table is not
   classified as a layout table.</p>
@@ -71001,6 +71049,10 @@
    <dd><cite><a href="http://dev.w3.org/2006/webapi/FileUpload/publish/FileAPI.html">File
    API</a></cite>, A. Ranganathan. W3C.</dd>
 
+   <dt id="refsFILESYSTEMAPI">[FILESYSTEMAPI]</dt>
+   <dd><cite><a href="http://dev.w3.org/2009/dap/file-system/file-dir-sys.html">File
+   API: Directories and System</a></cite>, E. Uhrhane. W3C.</dd>
+
    <dt id="refsGBK">[GBK]</dt>
    <dd><cite>Chinese Internal Code Specification</cite>. Chinese IT
    Standardization Technical Committee.</dd>
@@ -71048,6 +71100,9 @@
    character sets &mdash; Part 11: Latin/Thai
    alphabet</a></cite>. ISO.</dd>
 
+   <dt id="refsJPEG">[JPEG]</dt>
+   <dd><cite><a href="http://www.w3.org/Graphics/JPEG/jfif3.pdf">JPEG File Interchange Format</a></cite>, E. Hamilton.</dd>
+
    <dt id="refsJSURL">[JSURL]</dt>
    <dd><cite><a href="http://tools.ietf.org/html/draft-hoehrmann-javascript-scheme">The
    'javascript' resource identifier scheme</a></cite>,
@@ -71726,6 +71781,7 @@
   Krzysztof Maczy&#324;ski,
   &#40658;&#28580;&#21083;&#24535; (Kurosawa Takeshi),
   Kyle Hofmann,
+  Kyle Huey,
   L&eacute;onard Bouchet,
   Lachlan Hunt,
   Larry Masinter,
Received on Thursday, 12 May 2011 20:40:55 GMT

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