title: iOS GLSL. Is There A Way To Create An Image Histogram Using a GLSL Shader?
body: <p>Elsewhere on StackOverflow a question was asked regarding a depthbuffer histogram - <a href="https://stackoverflow.com/questions/5647727/create-depth-buffer-histogram-texture-with-glsl">Create depth buffer histogram texture with GLSL</a>. </p>
  
  <p>I am writing an iOS image-processing app and am intrigued by this question but unclear on the answer provided.  So, is it possible to create an image histogram using the GPU via GLSL?</p>