[] (0) More notes on what is a valid image.

git-svn-id: http://svn.whatwg.org/webapps@1958 340c8d12-0b0e-0410-8428-c7bf67bfef74

index

    content</a>.
 
   <p>The <code title=attr-img-src><a href="#src">src</a></code> attribute
-   must be present, and must contain a <a href="#valid">valid URL</a>.
-
-  <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?
+   must be present, and must contain a <a href="#valid">valid URL</a>
+   referencing a non-interactive, optionally animated, image resource that is
+   neither paged nor scripted.
+
+  <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>The requirements on the <code title=attr-img-alt><a
    href="#alt0">alt</a></code> attribute's value are described <a
    title="">official type</var>.
 
   <p>User agents must not support non-image resources with the <code><a
-   href="#img">img</a></code> element. User agents must not run executable
-   code (e.g. scripts) embedded in the image resource.
+   href="#img">img</a></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>This specification does not specify which image types are to be
+   supported.
 
   <hr>
 

source

   <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
   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>