title: Combine multiple opengl fragment shaders
body: <p>I'm wanting to port some image processing work to OpenGL for performance using OpenGL ES. I've got a very simple thresholding algorithm in place but I'd like to combine additional filters to the image (such as contrast).</p>
  
  <p>My first thought would be to complete this by using multiple fragment shaders. However, I'd like to do this pretty quickly so would this cause a lot of state change? The only method I've read about is to do this by working on a texture and then calling 'use program' multiple times.</p>
  
  <p>Is there a more efficient way to do this? Ideally, I'd like to perform a contrast stretch and a histogram balance as part of the steps. </p>
  
  <p>Unless I can combine this into a single shader would an FBO work for me here?</p>
  
  <p>I'm a bit new to OpenGL (in case you couldn't tell).</p>
  
  <p>Thanks!</p>
  
  <p>Simon</p>