Rotated licence plate detection
I have done the licence plate detection from Mastering OpenCV Book, But in my case the camera is not very parallel with the ground, so the plate may be rotated with even 45°... I have thought to search diagonal edges, but it seems it does not done directly, I have to rotate the searched image, that take some time. Do you suggest me some other approach, that can detect it even if rotated?
Another problem would be the colour, I have licence plates that are black and written with white or gray; red and written with blue, or green; yellow written with black; etc.
As far as experience in this matter goes for me, I have always built a license plate detector for each class of license plates. This means that I have another detector for Belgium than for The Netherlands for example, since their colors differ and thus their features will differ alot.
As to the rotation, that is hard one to deal with! You could try automatically rotating your image over a range of corners and see where the license plate detector has the highest certainty. Offcourse this will slow the process a lot.
So you used a detector based on lbp, or haar or features?
I would start with LBP, see how that goes, then depending on that decide to use other features or not.