Sobel operator for gradient angle

Question

I want to find the direction of the stroke in text. How can the Sobel operator be used for this purpose?

enter image description here

This image shows dp, which is the gradient direction. I wanted to know how I can apply the Sobel operator to find which pixel to choose, from p to q, along the path sp, to find the end pixel q on the edge.

score 11 · Accepted Answer · edited May 16 '18 at 20:01

11

You can find x derivative of image, then y derivative.

Sobel(Img,gxx,CV_32FC1,1,0); //  x derivative
Sobel(Img,gyy,CV_32FC1,0,1); //  y derivative

After that find phase http://docs.opencv.org/modules/core/doc/operations_on_arrays.html#phase

phase(gxx,gyy,angles,inDegrees);

edited May 16 '18 at 20:01

Daniel

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answered Mar 13 '14 at 15:23

Andrey Smorodov

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I don't think I found a built-in for finding magnitudes as well. Is there one? – a-Jays Nov 30 '14 at 17:16
2

Yes, take a look at cv::magnitude. http://docs.opencv.org/modules/core/doc/operations_on_arrays.html#magnitude – Andrey Smorodov Nov 30 '14 at 17:47

Sobel operator for gradient angle

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