How to detect occurrencies of a small image in a larger image?

Question

I would like to detect the occurrencies of a small image in a larger image, as well as coordinates.

How do I do it with C#/.NET?

Answer 1

Basic strategy.

1. Find descriptors that can fairly specifically describe (pinpoint) the small image and can be evaluated given a certain coordinate.
2. Find ways to evaluate that descriptor function at various locations in the larger image.
3. Find ways to make #2 fast. If not possible, go back to #1 and try another descriptor.

Useful ideas.

1. Phase correlation appears to be a hot technique on SO.

   • http://en.wikipedia.org/wiki/Phase_correlation
   • Phase correlation
   • Detecting if two images are visually identical
   • Numerical Pattern Matching

2. Image pyramid. (for its ability to speed up many classes of descriptors with minimal tinkering)

   • http://en.wikipedia.org/wiki/Pyramid_(image_processing)