08-16-2017, 09:48 PM
edge histogram descriptor using matlab code
This is the last kind of histograms I used in my project. The basic idea is to build a histogram with the directions of the gradients of the edges (borders or contours). It is possible to detect edges in an image but it in this we are interest in the detection of the angles. This is possible trough Sobel operators. The next five operators could give an idea of the strength of the gradient in five particular directions .
The convolution against each of this mask produce a matrix of the same size of the original image indicating the gradient (strength) of the edge in any particular direction. It is possible to count the max gradient in the final 5 matrix and use that to complete a histogram
In terms of avoiding the amount of non important gradients that could potentially be introduced by this methodology, an option is to just take into account the edges detected by a very robust method as the canny edge detector. This detector returns a matrix of the same size of the image with a 1 if there is an edge and 0 if there is not and edge. Basically it returns the contours of the objects inside the image. If you just consider the 1 s we are just counting the most pronounced gradients.