bug#10747: ImageMagick does not return much metadata

[Glenn Morris]

Package: emacs
Version: 24.0.93

As an example animated gif file, I use:
http://upload.wikimedia.org/wikipedia/commons/thumb/2/2c/Rotating_earth_%28large%29.gif/200px-Rotating_earth_%28large%29.gif

In an Emacs compiled with both libgif and ImageMagick support:

emacs -Q file.gif

then in the resulting image-mode buffer, 
(image-metadata (image-get-display-property))
returns:

(count 44 delay 0.09 extension-data (0 "control-chars" 255 "NETSCAPE2.0" 254
"File source: http://commons.wikimedia.org/wiki/File:Rotating_earth_(large).gif"
249 "control-chars"))

If I repeat the experiment with (I think this is the way to prefer
ImageMagick over libgif):

emacs -Q  --eval "(setq image-type-header-regexps nil)" \
  -f imagemagick-register-types 

then the returned metadata is just: (count 44)