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1958More notes on what is a valid image.2008-07-30 09:13
@@ -12973,26 +12973,31 @@ interface <dfn>HTMLImageElement</dfn> : <span>HTMLElement</span> {
 
   <p>An <code>img</code> element represents an image.</p>
 
   <p>The image given by the <dfn
   title="attr-img-src"><code>src</code></dfn> attribute is the
   embedded content, and the value of the <dfn
   title="attr-img-alt"><code>alt</code></dfn> attribute is the
   <code>img</code> element's <span>fallback content</span>.</p>
 
   <p>The <code title="attr-img-src">src</code> attribute must be
-  present, and must contain a <span>valid URL</span>.</p>
-
-  <p class="big-issue">Should we restrict the URL to pointing to an
-  image? What's an image? Is PDF an image? (Safari supports PDFs in
-  &lt;img> elements.) How about SVG? (Opera supports those). WMFs?
-  XPMs? HTML?</p>
+  present, and must contain a <span>valid URL</span> referencing a
+  non-interactive, optionally animated, image resource that is neither
+  paged nor scripted.</p>
+
+  <p class="note">Images can thus be static bitmaps (e.g. PNGs, GIFs,
+  JPEGs), single-page vector documents (single-page PDFs, XML files
+  with an SVG root element), animated bitmaps (APNGs, animated GIFs),
+  animated vector graphics (XML files with an SVG root element that
+  use declarative SMIL animation), and so forth. However, this also
+  precludes SVG files with script, multipage PDF files, interactive
+  MNG files, HTML documents, plain text documents, and so forth.</p>
 
   <p>The requirements on the <code title="attr-img-alt">alt</code>
   attribute's value are described <a href="#alt">in the next
   section</a>.</p>
 
   <p class="big-issue">There has been some suggestion that the <code
   title="">longdesc</code> attribute from HTML4, or some other
   mechanism that is more powerful than <code title="">alt=""</code>,
   should be included. This has not yet been considered.</p>
 
@@ -13077,22 +13082,30 @@ interface <dfn>HTMLImageElement</dfn> : <span>HTMLElement</span> {
   <p class="note">This allows servers to return images with error
   responses, and have them displayed.</p>
 
   <p>The user agents should apply the <span title="Content-Type
   sniffing: image">image sniffing rules</span> to determine the type
   of the image, with the image's <span title="Content-Type">associated
   Content-Type headers</span> giving the <var title="">official
   type</var>.</p>
 
   <p>User agents must not support non-image resources with the
-  <code>img</code> element. User agents must not run executable code
-  (e.g. scripts) embedded in the image resource.</p>
+  <code>img</code> element (e.g. XML files whose root element is an
+  HTML element). User agents must not run executable code
+  (e.g. scripts) embedded in the image resource. User agents must only
+  display the first page of a multipage resource (e.g. a PDF
+  file). User agents must not allow the resource to act in an
+  interactive fashion, but should honour any animation in the
+  resource.</p>
+
+  <p>This specification does not specify which image types are to be
+  supported.</p>
 
   <hr>
 
   <p>The <code title="attr-hyperlink-usemap">usemap</code> attribute,
   if present, can indicate that the image has an associated
   <span>image map</span>.</p>
 
   <p>The <dfn title="attr-img-ismap"><code>ismap</code></dfn>
   attribute, when used on an element that is a descendant of an
   <code>a</code> element with an <code

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