Improve corner marker detection
Related to #376.
This MR changes the corner marker detection. To start, it incorporates the check for valid corner markers into the find corner marker function. This function now works like this:
- Search for corner markers in a box 1/8 the dimensions of the full page
- If less than two corner markers are found, continue with a larger box
- If 2 corner markers are found, save these as the best so far, and continue with a larger box
- If 3 or more are found, return these corner points
- If there are no more box sizes to check, return the best corner markers found so far, otherwise raise an error.
Edited by Hugo Kerstens