python - 使用 OpenCV Python 用霍夫变换裁剪圆

Question

我想从下面的虹膜图像中裁剪圆圈：

这是我的圆圈检测代码：

from matplotlib import pyplot as plt
import numpy as np
import cv2

gambar = cv2.imread('tes2.jpg',0)
cimg = cv2.cvtColor(gambar,cv2.COLOR_GRAY2BGR)
canny = cv2.Canny(cimg,50,50)

circles = cv2.HoughCircles(canny,cv2.HOUGH_GRADIENT,1,10000,
                    param1=50,param2=30,minRadius=50,maxRadius=200)

circles = np.uint16(np.around(circles))
for i in circles[0,:]:
    # draw the outer circle
    cv2.circle(cimg,(i[0],i[2]),i[2],(0,255,0),2)
    # draw the center of the circle
    cv2.circle(cimg,(i[0],i[2]),2,(0,0,255),3)

plt.imshow(cimg,cmap = 'gray')
plt.show()

但是，我不知道如何裁剪这个圆圈（虹膜定位）。我一直在关注这个代码参考Cropping circle from the image using OpenCV python。这是我下面的裁剪图像代码：

from matplotlib import pyplot as plt
import numpy as np
import cv2

gambar1 =cv2.imread('tes2.jpg') 
gambar = cv2.imread('tes2.jpg',0)
cimg = cv2.cvtColor(gambar,cv2.COLOR_BGR2GRAY)
ret, thresh = cv2.threshold(cimg, 50, 255, cv2.THRESH_BINARY)

# Create mask
height,width = gambar.shape
mask = np.zeros((height,width), np.uint8)

canny = cv2.Canny(thresh,100,200)


gray = cv2.cvtColor(gambar,cv2.COLOR_GRAY2BGR)

circles = cv2.HoughCircles(canny,cv2.HOUGH_GRADIENT,1,10000,
                    param1=50,param2=30,minRadius=0,maxRadius=0)


for i in circles[0,:]:
    cv2.circle(mask,(i[0],i[1]),i[2],(255,255,255),thickness=-1)

masked_data = cv2.bitwise_and(gambar1, gambar1, mask=mask)

# Apply Threshold
_,thresh = cv2.threshold(mask,1,255,cv2.THRESH_BINARY)

# Find Contour
contours = cv2.findContours(thresh,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_SIMPLE)
x,y,w,h = cv2.boundingRect(contours[0])

# Crop masked_data
crop = masked_data[y:y+h,x:x+w]

plt.imshow(gambar1,cmap = 'gray')
plt.imshow(crop, cmap='gray')
plt.show()

但是，当我尝试使用上面的参考代码时，会出现如下错误：

File "C:/Users/zurri/spyder/masktes.py", line 14, in <module>
cimg = cv2.cvtColor(gambar,cv2.COLOR_BGR2GRAY)
error: OpenCV(4.2.0) c:\projects\opencv-python\opencv\modules\imgproc\src\color.simd_helpers.hpp:92: error: (-2:Unspecified error) in function '__cdecl cv::impl::`anonymous-namespace'::CvtHelper<struct cv::impl::`anonymous namespace'::Set<3,4,-1>,struct cv::impl::A0xe227985e::Set<1,-1,-1>,struct cv::impl::A0xe227985e::Set<0,2,5>,2>::CvtHelper(const class cv::_InputArray &,const class cv::_OutputArray &,int)'
Invalid number of channels in input image:
     'VScn::contains(scn)'
 where
     'scn' is 1

谁能帮我解决这个问题？我只是想用openCV python裁剪这个圆圈（虹膜定位），谢谢

Answer 1

解释

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findContours方法使用Suzuki算法从给定的二值图像中检索轮廓。轮廓对于形状分析、对象检测和识别很有用。

该findContour方法返回两个变量：contours和hierarchy。在您所做的原始代码contours = cv2.findContour(...)中，您结合了contours和hierarchy变量。因此你有一个错误。我们根本不需要hieararchy变量，因此我们放置了_. 于是错误就解决了。

解决方案

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用以下内容替换该findContours行：

contours, _ = cv2.findContours(thresh,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_SIMPLE)

结果：