OpenCV - Finding the outline of Canny edges

Question

I have used Canny edge detector to detect the edges of an image. The results are shown below:

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I would like to remove everything except for the outline of the edges. The desired output is shown below:

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I have tried a series of morphological transformations (specifically eroding/dilating and opening/closing), however, these transformations also removed the outline of the image. I tried using median blurring, but that also removed the outline edges.

Answer 1

You can select the Region of Interest by selecting five points of a polygon like the one shown and use Numpy's polyfit function to fit lines of a polygon and meshgrid to find region inside, to mask the edges inside your selected region and obtain everything else from outside.