Crop an image in PIL using the 4 points of a rotated rectangle

Question

I have a list of four points of a rotated rectangle in the form of:

points = [[x1, y1], [x2, y2], [x3, y3], [x4, y4]]

I can crop in PIL using:

img.crop((x1, y1, x2, y2))

But this doesn't work with a rotated rectangle. Just to clarify I want the resulting cropped image to be rotated so the cropped area becomes a non-rotated rectangle.

I am willing to use openCV, although would like to avoid it as the conversion of an image from PIL to openCV takes time, and I will be itterating through this process about 100 times.

Answer 1

If you start with this image:

You can do it like this using a QuadTransform:

#!/usr/bin/env python3

from PIL import Image, ImageTransform

# Open starting image and ensure RGB
im = Image.open('a.png').convert('RGB')

# Define 8-tuple with x,y coordinates of top-left, bottom-left, bottom-right and top-right corners and apply
transform=[31,146,88,226,252,112,195,31]
result = im.transform((200,100), ImageTransform.QuadTransform(transform))

# Save the result
result.save('result.png')