title: Compare images in C# .NET
body: <p>I have a scanned image of a document which has multiple boxes which may or may not contain signatures. I am able to identify the boxes, but now I want to figure out which boxes contain signatures. I tried to compare the image with the reference blank box image. Ideally pixel match should do,but my images can be tilted by some angle, which makes it tough. I am programming in .NET.</p>
  
  <p>Any suggestions?</p>
  
  <p>Edited on Jan 04:
  I have asked this question on Nov 25. At that time, the solution proposed was to check count the number of black pixels in the image. That worked for me. However, the performance of the application is bad now. Because, it has to check black pixels on 20 rectangles of 100*1000 size.</p>
  
  <p>Is there any better to solution to determine if a image is blank?</p>