minAreaRect OpenCV [Python]返回的裁剪矩形 [英] Crop Rectangle returned by minAreaRect OpenCV [Python]

问题描述

minAreaRect 返回一个旋转的矩形。如何裁剪矩形内部图像的这一部分？

minAreaRect in OpenCV returns a rotated rectangle. How do I crop this part of the image which is inside the rectangle?

boxPoints 返回旋转矩形的角点的坐标，以便通过循环访问像素通过框内的点，但有没有更快的方法在Python中裁剪？

boxPoints returns the co-ordinates of the corner points of the rotated rectangle so one can access the pixels by looping through the points inside the box, but is there a faster way to crop in Python?

编辑

参见代码在我的答案中。

推荐答案

您还没有提供示例代码，所以我也在没有代码的情况下回答。
您可以按以下步骤操作：

You have not given sample code, so I am answering without code also. You could proceed as follows:

1. 从矩形的角落确定旋转角度α与水平轴的对比。


2. 按alpha旋转图像，使裁剪的矩形与图像边框平行。确保临时图像的大小更大，以免信息丢失（参见：无图像旋转图像裁剪OpenCV ）


3. 使用numpy切片裁剪图像（cf：如何使用Python在OpenCV中裁剪图像）


4. 通过-alpha转回图像。

1. From corners of rectangle, determine angle alpha of rotation against horizontal axis.
2. Rotate image by alpha so that cropped rectangle is parallel to image borders. Make sure that the temporary image is larger in size so that no information gets lost (cf: Rotate image without cropping OpenCV)
3. Crop image using numpy slicing (cf: How to crop an image in OpenCV using Python)
4. Rotate image back by -alpha.

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