我如何从图像中剪裁一个凹多边形。 我的输入图像看起来像是
。
并且封闭多边形的坐标为
[10,150],[150,100],[300,150],[350,100],[310,20],[35,10]。我想使用opencv剪裁由凹多边形界定的区域。我搜索了其他类似的问题,但没有找到正确的答案。这就是为什么我要问它?能帮帮我吗?
非常感谢任何帮助!
![this](https://istack.dev59.com/qrJTd.webp)
非常感谢任何帮助!
步骤
- 使用多边形点找到区域
- 使用多边形点创建遮罩层
- 进行遮罩操作以进行裁剪
- 如有需要,添加白色背景
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)
源图片:
结果:
您可以通过以下3个步骤完成:
使用图像创建蒙版
mask = np.zeros((height, width)) points = np.array([[[10,150],[150,100],[300,150],[350,100],[310,20],[35,10]]]) cv2.fillPoly(mask, points, (255))
将蒙版应用于原始图像
res = cv2.bitwise_and(img,img,mask = mask)
可选择性地裁剪图像以缩小大小
rect = cv2.boundingRect(points) # 返回矩形的(x,y,w,h) cropped = res[rect[1]: rect[1] + rect[3], rect[0]: rect[0] + rect[2]]
这样最终您应该得到已剪裁的图像。
为了完整起见,这是完整代码:
import numpy as np
import cv2
img = cv2.imread("test.png")
height = img.shape[0]
width = img.shape[1]
mask = np.zeros((height, width), dtype=np.uint8)
points = np.array([[[10,150],[150,100],[300,150],[350,100],[310,20],[35,10]]])
cv2.fillPoly(mask, points, (255))
res = cv2.bitwise_and(img,img,mask = mask)
rect = cv2.boundingRect(points) # returns (x,y,w,h) of the rect
cropped = res[rect[1]: rect[1] + rect[3], rect[0]: rect[0] + rect[2]]
cv2.imshow("cropped" , cropped )
cv2.imshow("same size" , res)
cv2.waitKey(0)
使用彩色背景版本,可以像这样使用代码:
import numpy as np
import cv2
img = cv2.imread("test.png")
height = img.shape[0]
width = img.shape[1]
mask = np.zeros((height, width), dtype=np.uint8)
points = np.array([[[10,150],[150,100],[300,150],[350,100],[310,20],[35,10]]])
cv2.fillPoly(mask, points, (255))
res = cv2.bitwise_and(img,img,mask = mask)
rect = cv2.boundingRect(points) # returns (x,y,w,h) of the rect
im2 = np.full((res.shape[0], res.shape[1], 3), (0, 255, 0), dtype=np.uint8 ) # you can also use other colors or simply load another image of the same size
maskInv = cv2.bitwise_not(mask)
colorCrop = cv2.bitwise_or(im2,im2,mask = maskInv)
finalIm = res + colorCrop
cropped = finalIm[rect[1]: rect[1] + rect[3], rect[0]: rect[0] + rect[2]]
cv2.imshow("cropped" , cropped )
cv2.imshow("same size" , res)
cv2.waitKey(0)
对于模糊图像背景版本,请使用以下代码:
img = cv2.imread(img_path)
box = <box points>
# -- background
blur_bg = cv2.blur(img, (h, w))
mask1 = np.zeros((h, w, 3), np.uint8)
mask2 = np.ones((h, w, 3), np.uint8) * 255
cv2.fillPoly(mask1, box, (255, 255, 255))
# -- indexing
img_idx = np.where(mask1 == mask2)
bg_idx = np.where(mask1 != mask2)
# -- fill box
res = np.zeros((h, w, 3), np.int64)
res[img_idx] = img[img_idx]
res[bg_idx] = blur_bg[bg_idx]
res = res[y1:y2, x1:x2, :]