title: What do the elements in a homography matrix mean?
body: <p>I'm new to image processing, but I'm using EMGU for C# image analysis. However, I know the homography matrix isn't unique to EMGU, and so perhaps someone with knowledge of another language can explain better.</p>
  
  <p>Please (in as simplified as can be) can someone explain what each element does. I've looked this up online but can't find an answer that I can properly understand (as I said, I'm kinda new to all this!)</p>
  
  <p>I analyse 2 images, both 2 dimensional. Therefore a 3x3 matrix is needed to account for the rotation / translation of the image. If no movement is detected, the homography matrix is:
  100,
  010,
  001</p>
  
  <p>I know from research (eg <a href="https://stackoverflow.com/questions/9275567/opencv-homography-transform-a-point-what-is-this-code-doing">OpenCV Homography, Transform a point, what is this code doing?</a>) that:
  10Tx,
  01Ty,
  XXX </p>
  
  <p>The 10,01 bit is the rotation of the x and y coordinates. The Tx and Ty bits are the translational movement, but what is the XXX bit? This is what I don't understand? Is it something to do with affine transformations? Please can someone explain:
  1. If I'm currently right in what I say above.
  2. what the XXX bit means</p>