Weird edge detection behavior when the blurred image border pixel extrapolation method changes

[Rektino]

Expected behaviour

The canny edge detector should yield very similar images when the blurred image has two different pixel extrapolation methods for the border, since only the border is affected by this.

Actual behaviour

Edge detection is being affected by the selected method. When I select cv.BORDER_REPLICATE I get many more edges than when cv.BORDER_DEFAULT is selected. This does not make sense.

Steps to reproduce

Code running on Windows 11 OpenCV version : 4.10.0 Python version : 3.11.4

CODE :

img = cv.imread('../Photos/park.jpg') #Gaussian blur blur1 = cv.GaussianBlur(img , (7,7) , cv.BORDER_REPLICATE) blur2 = cv.GaussianBlur(img, (7,7) , cv.BORDER_DEFAULT) cv.imshow('Original' , img) cv.imshow('Blurred 1' , blur1) cv.imshow('Blurred 2' , blur2)

#Canny edge detector: canny1 = cv.Canny(blur1 , 150,210) cv.imshow('Canny (1) edges w/ 150-210' , canny1)

canny2 = cv.Canny(blur2 , 150 , 210) cv.imshow('Canny (2) edges w/ 150-210' , canny2)