Python错误集锦：OpenCV calcHist()计算直方图时提示 opencv-4.5.3\modules\imgproc\src\histogram.cpp:160: error: (-215:Assertion failed) j < nimages in function 'cv::histPrepareImages'

原文链接：http://www.juzicode.com/python-error-opencv-j-nimages-in-function-cv-histprepareimages

错误提示：

calcHist()计算直方图时提示 opencv-4.5.3\modules\imgproc\src\histogram.cpp:160: error: (-215:Assertion failed) j < nimages in function ‘cv::histPrepareImages’

#VX公众号: 桔子code / juzicode.com
import matplotlib.pyplot as plt
import numpy as np
import cv2  
print('cv2.__version__:',cv2.__version__)

img_src = cv2.imread('lena.jpg') 
histSize = 256
histRange = (0, histSize)  
b_hist = cv2.calcHist([img_src], [3], None, [histSize], histRange,accumulate=True)  
plt.title('b hist')
plt.plot(b_hist) 
plt.show() 

==========运行结果：
cv2.__version__: 4.5.3
---------------------------------------------------------------------------
error                                     Traceback (most recent call last)
<ipython-input-11-15f23d74ec76> in <module>
      8 histSize = 256
      9 histRange = (0, histSize)
---> 10 b_hist = cv2.calcHist([img_src], [3], None, [histSize], histRange,accumulate=True)
     11 plt.title('b hist')
     12 plt.plot(b_hist)

error: OpenCV(4.5.3) E:\juzicode\opencv-4.5.3\modules\imgproc\src\histogram.cpp:160: error: (-215:Assertion failed) j < nimages in function 'cv::histPrepareImages'

错误原因：

1、calcHist()第2个入参channels对应的[3]指定的通道号3对于输入的图像img_src来说不存在，img_src通过默认方式读入时通道号编号从0-2，需要修改为对应的通道号。

解决方法：

1、修改calcHist()第2个入参channels参数为0,1或2：

#VX公众号: 桔子code / juzicode.com
import matplotlib.pyplot as plt
import numpy as np
import cv2  
print('cv2.__version__:',cv2.__version__)

img_src = cv2.imread('lena.jpg') 
histSize = 256
histRange = (0, histSize)  
b_hist = cv2.calcHist([img_src], [2], None, [histSize], histRange,accumulate=True)  
plt.title('b hist')
plt.plot(b_hist) 
plt.show() 

扩展内容：

1. OpenCV-Python教程

---

如果本文还没有完全解决你的疑惑，你也可以在微信公众号“桔子code”后台给我留言，欢迎一起探讨交流。