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Why python "line()" draw one line when called three times ?

asked 2014-03-26 10:54:48 -0500

Guido gravatar image

Hi,

I am trying to draw a coordinate frame on an image from some points. The code is the following

def draw(img, corners):
points = tuple(map(tuple, corners))
img = cv2.line(img, points[0], points[1], (0,0,255), 3)
img = cv2.line(img, points[0], points[2], (0,255,0), 3)
img = cv2.line(img, points[0], points[3], (255,0,0), 3)
return img

However, only the first of the three lines is drawn. Any idea on what is going wrong ?

Guido

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Make sure that your points are not equal or out of bound.

Haris gravatar imageHaris ( 2014-03-26 11:31:16 -0500 )edit

Alright I solve this, and there were two errors. First, I wasn't retrieving the returned image. Seconde cv2.line doesn't return an image (it returns none) I got misled by the opencv 3.0.0 documentation.

Guido gravatar imageGuido ( 2014-03-26 11:38:53 -0500 )edit

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answered 2014-03-26 11:39:11 -0500

Guido gravatar image

updated 2014-03-26 11:41:06 -0500

Alright I solved this, and there were two errors. First, I wasn't retrieving the returned image. Second cv2.line doesn't return an image (it returns none) I got misled by the opencv 3.0.0 documentation.

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Asked: 2014-03-26 10:54:48 -0500

Seen: 88 times

Last updated: Mar 26 '14