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Error with findContours()

asked 2018-10-15 04:46:29 -0500

I'm getting the following error here:

error: (-215) scn == 3 || scn == 4 in function cv::cvtColor This is my code

def detectBoxes(img):
    image = np.asarray(img)
    gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
    gradient = cv2.Laplacian(gray, cv2.CV32F)
    kernel = np.ones((15,15),np.uint8)
    closing = cv2.morphologyEx(gradient, cv2.MORPH_CLOSE, kernel)
    closing = cv2.cvtColor(closing, cv2.COLOR_BGR2GRAY)
    im2, cnts, hier = cv2.findContours(closing, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_NONE)

I think it's because findContours needs another type of color conversion, but I'm unsure about which one. Any clues here? Thanks

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your image was either invalid (python noobs never seem to understand it), or already grayscale

berak gravatar imageberak ( 2018-10-15 05:02:35 -0500 )edit

I don't think that the image is invalid (I've done similar approaches with other functions in the same code and everything runs well) nor it's already grayscale (when I remove the second cvtColor, I've got another error: FindContours supports only CV_8UC1 images...)

norhther gravatar imagenorhther ( 2018-10-15 05:10:17 -0500 )edit

the lesson is: you have to check , not think.

berak gravatar imageberak ( 2018-10-15 05:10:59 -0500 )edit

image = np.asarray(img) <-- what is this for ? shouldn't it have a type, too ? what is the result type now ?

again, why ? opencv's images are all numpy arrays already.

berak gravatar imageberak ( 2018-10-15 05:14:16 -0500 )edit

You can just use opencv's image reading mechanism. It is already a numpy array. Try removing that line.

opencv-newb gravatar imageopencv-newb ( 2018-10-15 06:54:48 -0500 )edit

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answered 2018-11-19 19:06:36 -0500

supra56 gravatar image

This should work too. image = np.asarray(img).copy()

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Asked: 2018-10-15 04:46:29 -0500

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Last updated: Nov 19 '18