3 ms·
is canny edge detection better than adaptivethreshold for pre-filtering the image? The AR tag implementations I've looked at all seem to use adaptivethreshold.
by Jack000 10y ago
is canny edge detection better than adaptivethreshold for pre-filtering the image? The AR tag implementations I've looked at all seem to use adaptivethreshold.
- eikaramba 10y agoco-founder of fileee.com here(we do that for a living :) ). I can tell you that in general adaptivethreshold is better, because it is less error prone against low contrast situations and missing edges. That said there are also cases where canny performs better. That's why we actually decided to use a machine learning approach to decide when to use what. There are even more things one can do to improve the detection(e.g. hough tranform to find edges or use variance or fft to assest whether possible "document" candidates are just garbage rectangles or real documents.)
- mendeza 10y agoI am interested in learning more about using variance and fft to finding boundary in documents? Can you elaborate or link any good resources to learn more about this, I'm very interested in learning :)
- nojvek 10y agocanny and adaptive threshold can go hand in hand. i.e you can threshold an image and then apply canny. Adaptive threshold turns the image into binary (either white or black) and it works great when there are big shadows. e.g http://www.aforgenet.com/framework/docs/html/img/imaging/sample20.png http://www.aforgenet.com/framework/docs/html/img/imaging/sam... -> http://www.aforgenet.com/framework/docs/html/img/imaging/bradley_local_thresholding.png http://www.aforgenet.com/framework/docs/html/img/imaging/bra...