How to detect 45 degree edges in an image

Question

If instead of getting all edges, I only want edges that make 45 degree angles. What is a method to detect these?

Would it be possible to detect all edges, then somehow run a constrained hough transform to detect which edges form 45 degrees?

Answer 1

What is wrong with using an diagonal structure element and simply convolve the image??

Details

Please read here and it should become clear how to build the structuring element. If you are familiar with convolution than you can build a simple structure matrix which amplifies diagonals without theory

{ 0,  1,  2}, 
{-1,  0,  1}, 
{-2, -1,  0}

The idea is: You want to amplify pixel in the image, where 45deg below it is something different than 45deg above it. Thats the case when you are at a 45deg edge.

Taking an example. Following picture

convolved by the above matrix gives a graylevel image where the highest pixel values have those lines which are exactly 45deg.

Now the approach is to simply binarize the image. Et voila