使用Opencv python从图像裁剪凹面多边形 [英] Cropping Concave polygon from Image using Opencv python

问题描述

如何从图像中裁剪出凹面多边形.我的输入图片看起来像 .

How can I crop a concave polygon from an image. My Input image look like .

和闭合多边形的坐标为 [10,150]，[150,100]，[300,150]，[350,100]，[310,20]，[35,10].我希望使用opencv裁剪以凹面多边形为边界的区域.我搜索了其他类似的问题，但是找不到正确的答案.这就是为什么我要问它?你能帮我吗?

and the coordinates of closed polygon are [10,150],[150,100],[300,150],[350,100],[310,20],[35,10]. I want region bounded by concave polygon to be cropped using opencv. I searched for other similar questions but I did not able to find correct answer. That's why I am asking it ? Can you help me.

任何帮助将不胜感激.!!!

Any help would be highly appreciated.!!!

推荐答案

步骤

1. 使用多点查找区域
2. 使用多点创建蒙版
3. 遮罩进行修剪
4. 根据需要添加白色bg

1. find region using the poly points
2. create mask using the poly points
3. do mask op to crop
4. add white bg if needed

代码:

# 2018.01.17 20:39:17 CST
# 2018.01.17 20:50:35 CST
import numpy as np
import cv2

img = cv2.imread("test.png")
pts = np.array([[10,150],[150,100],[300,150],[350,100],[310,20],[35,10]])

## (1) Crop the bounding rect
rect = cv2.boundingRect(pts)
x,y,w,h = rect
croped = img[y:y+h, x:x+w].copy()

## (2) make mask
pts = pts - pts.min(axis=0)

mask = np.zeros(croped.shape[:2], np.uint8)
cv2.drawContours(mask, [pts], -1, (255, 255, 255), -1, cv2.LINE_AA)

## (3) do bit-op
dst = cv2.bitwise_and(croped, croped, mask=mask)

## (4) add the white background
bg = np.ones_like(croped, np.uint8)*255
cv2.bitwise_not(bg,bg, mask=mask)
dst2 = bg+ dst


cv2.imwrite("croped.png", croped)
cv2.imwrite("mask.png", mask)
cv2.imwrite("dst.png", dst)
cv2.imwrite("dst2.png", dst2)

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源图像:

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Source image:

结果:

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