title: CNN for image to feature vector
body: <p>I have a rather simple question, but I cannot wrap my head around this. You need to correct me in the case that I have understood something wrong!!! Typically, CNNs are used for image classification, where the FC layers are used to output the probability per given class.</p>
  <p><strong>I want actually something else:</strong>
  Can I train a CNN to output a feature vector? One example would be: Input==Image; Output==Color histogram with 3 channels (RGB) and every channel value is the number of red, green, blue pixels.
  (I actually want to learn other image feature descriptors for special images, but that should then work analogous).</p>
  <p><em>Pointers, Links and Tutorials</em> (esp. <strong>code</strong> that I can modify for my purposes) would be greatly appreciated.</p>
  <p>Thanks so much in advance!!</p>