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Kenil Vasani
Kenil Vasani

Kenil Vasani

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Asked: 2020-12-14T21:05:34+00:00 In:

OpenCV error – cv2.cvtcolor

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I am a newbie to openCV and I am stuck at this error with no resolution. I am trying to convert an image from BGR to grayscale format using this code-

img = cv2.imread('path//to//image//file')
gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)

This seems to be working fine. I checked the data type of the img variable which turns out to be numpy ndarray and shape to be (100,80,3). However if I give an an image already present in code of numpy ndarray data type and of same dimensions as input to the cvtColor function, it gives me the following error-

Error: Assertion failed (depth == 0 || depth == 2 || depth == 5) in cv::cvtColor, file D:\Build\OpenCV\opencv-3.4.1\modules\imgproc\src\color.cpp, line 11109
cv2.error: OpenCV(3.4.1) D:\Build\OpenCV\opencv-3.4.1\modules\imgproc\src\color.cpp:11109: error: (-215) depth == 0 || depth == 2 || depth == 5 in function cv::cvtColor

The code for the second case is (making a custom np.ndarray over here)-

img = np.full((100,80,3), 12)
gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)

Can anyone clarify what is the reason for this error and how to rectify it?

image-processingopencvpython
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    1. Kenil Vasani

      Kenil Vasani

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      This is because your numpy array is not made up of the right data type. By default makes an array of type np.int64 (64 bit), however, cv2.cvtColor() requires 8 bit (np.uint8) or 16 bit (np.uint16). To correct this change your np.full() function to include the data type:

      img = np.full((100,80,3), 12, np.uint8)

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