opencv python cv2.line works only for certain pixel values

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I am using cv2.line to draw vertical lines across my image. The command works for certain values of pixels but not for all of them. For example I can draw a line through pixels (21,1) to (21,450) but not through (160,1) to (160,450). I am sure my image is larger than 160 pixels. I have used different values and it seems random to me in which values the line is printed and in which values it is not. Here is my code (I am working with Jupiter notebook):

cv2.line

new_im = cv2.cvtColor(edge, cv2.COLOR_GRAY2RGB)
cv2.line(new_im,(21,1),(21,450),(255,0,0),1)
cv2.line(new_im,(50,1),(50,450),(255,0,0),1)
cv2.line(new_im,(100,1),(100,450),(255,0,0),1)
cv2.line(new_im,(150,1),(150,450),(255,0,0),1)
cv2.line(new_im,(155,1),(155,450),(255,0,0),1)
cv2.line(new_im,(165,1),(165,450),(255,0,0),1)
plt.imshow(new_im)
plt.show()


I have also tried to change the order of the lines but I get the same result. Some lines are printed and some are not.

new_im.shape

1 Answer
1

imshow defaults to nearest neighbor interpolation in some backends.

If the view is smaller than the original image, some rows may be dropped and not displayed at all.

Fix it by explicitly setting an appropriate interpolation string, e.g. bilinear:

plt.imshow(new_im, interpolation="bilinear")


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