title: How to get texture data using textureID's in openGL
body: <p>I'm writing some code where all I have access to is a textureID to get access to the required texture. Is there any way that I can get access to the RGB values of this texture so I can perform some computations on it?</p>
  
  <p>EDIT: I am looking for the inverse of <code>glTexSubImage2D</code>. I want to get the texture data rather than replace it.</p>