using HAAR training for post-it note recognition

Question

I need to be able to detect a variety of coloured post-it notes via a Microsoft Kinect video stream. I have tried using Emgucv for edge detection but it doesn't seem to locate the vertices/edges and also colour segmentation/detection however considering the variety of colours that may not be robust enough.

I am attempting to use HAAR classification. Can anyone suggest the best variety of positive/negative images to use. For example, for the positive images should I take pictures of many different coloured post-it notes in various lighting conditions and orientations? Seeing as it is quite a simple shape ( a square) is using HAAR classification over-complicating things?

Answer 1

I haar classifiers are typically used on black and white images and trigger primarily on morphologic edge like feature. Seems like if you want to find post it notes in an image the easiest method would be to look at colors (since they come in very distinct colors). Have you tried training a SVM of Random forest classifier to detect post it notes based on just color? Once you've identified areas in the image that are probably post it notes you could start looking at things like the shape as additional validation that you are indeed looking at a post it note.

Take a look at the following as an example of how to find rectangles in an image using hough transform: https://opencv-code.com/tutorials/automatic-perspective-correction-for-quadrilateral-objects/