Erroneous behavior of `four_point_transform`

PyImageSearch / imutils

A series of convenience functions to make basic image processing operations such as translation, rotation, resizing, skeletonization, and displaying Matplotlib images easier with OpenCV and Python.

MIT License

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Erroneous behavior of `four_point_transform` #195

Open cedric-sun opened 4 years ago

cedric-sun commented 4 years ago

Hi all,

I found some weird behavior of imutils.perspective.four_point_transform. The following example was meant to get a perpendicular perspective of a car license plate:

The image is available here. Coordinates in br-bl-tl-tr order are [(481, 580), (254, 615), (255, 551), (482, 516)] (well, the x coordinates are just 1 pixel away)

The notecard demo works fine for me. I guess something is wrong with the order_points function.

cedric-sun commented 4 years ago

I think cv2.warpPerspective requires that these 4 points in the tl-tr-bl-br order, but the result of order_points is interpreted as

https://github.com/jrosebr1/imutils/blob/df65a77087548b5952431cc8006d66bcca7b1abc/imutils/perspective.py#L40

Something might be wrong.