You could also try the following strategy:
- Extract the features
- Match the features (via FLANN, for most cases the fastest choice)
- Compute a homography via RANSAC
- Use the homography to warp the detected object from your scene image in the direction of your pattern image. If you do it right, both images must have the same dimension.
- Use a similarity measure for your warped and pattern image. For example a normalized cross-correlation will do fine. Or a normalized correlation coefficient...
