Detecting outer most-edge of image and plotting based on it

Question

I\'m working on a project that can calculate the angle of an elbow joint by image. The part I\'m struggling on is the image processing.

Currently doing this in Pytho

Answer 1

As you can see, the line in the binary image is not that straight, also there are so many lines similar. So directly doing HoughLine on such an image is a bad choice, not responsibility.

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I try to binary the image , drop the left-top region (3*w/4, h*2/3), then I get the two separate regions:

img = cv2.imread("img04.jpg", 0)
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
th, threshed = cv2.threshold(gray, 100, 255, cv2.THRESH_BINARY_INV|cv2.THRESH_OTSU)
H,W = img.shape[:2]
threshed[:H*2//3,:W*3//4] = 0

cv2.imwrite("regions.png", threshed)

Then you can do other post steps as you like.