title: RMagick - ImageMagick gives error "no decode delegate for this image format"
body: <p>The problem occurs when i try to manipulate an image uploaded from sinatra. </p>
  
  <pre><code>File.open(params[:file][:tempfile]) do |p|
     thumb = Magick::Image.read(p)
     thumb.crop_resized!(75, 75, Magick::NorthGravity)
  end
  </code></pre>
  
  <p>The uploaded file is a jpeg, form data when uploading image includes</p>
  
  <pre><code>{:filename=&gt;"299732_176749115737355_100002068035867_380115_618512842_n.jpg",    :type=&gt;"image/jpeg", :name=&gt;"file", :tempfile=&gt;#&lt;File:/var/folders/hf/d6vx6vg56nbd5n44jjrp84k80000gn/T/RackMultipart20120228-55947-1fd2l6c&gt;, :head=&gt;"Content-Disposition: form-data; name=\"file\"; filename=\"299732_176749115737355_100002068035867_380115_618512842_n.jpg\"\r\nContent-Type: image/jpeg\r\n"}
  </code></pre>
  
  <p>And also ImageMagick has the necessary delegates</p>
  
  <pre><code>convert -list configure
  </code></pre>
  
  <p>returns</p>
  
  <pre><code>DELEGATES     bzlib freetype jpeg jng jp2 lcms png tiff x11 xml zlib
  </code></pre>
  
  <p>So, i should be able to upload and transform a jpeg, but it whines about delegates.
  Also i am working on Mac OSX 10.7, maybe another weird problem with mac</p>