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Failure to use adaptiveThreshold: CV_8UC1 in function adaptiveThreshold

Tags:

python

opencv

I have used openCV python and encountered an error.

img_blur = cv2.medianBlur(self.cropped_img,5)
img_thresh_Gaussian = cv2.adaptiveThreshold(img_blur, 255, cv2.ADAPTIVE_THRESH_GAUSSIAN_C, cv2.THRESH_BINARY, 11, 2)

plt.subplot(1,1,1),plt.imshow(img_thresh_Gaussian, cmap = 'gray')
plt.title("Image"), plt.xticks([]), plt.yticks([])
plt.show()

but I received:

cv2.error: /home/phuong/opencv_src/opencv/modules/imgproc/src/thresh.cpp:1280: error: (-215) src.type() == CV_8UC1 in function adaptiveThreshold

Do I have to install something else?

like image 852
PhuongHoang Avatar asked Nov 19 '14 10:11

PhuongHoang


4 Answers

The problem is that you are trying to use adaptive thresholding to an image that is not in greyscale. And the function only works with a greyscale images.

So you have to convert your image to a greyscale format as it is described in documentation.

They read the image in a greyscale format with: img = cv2.imread('dave.jpg',0). You can also convert it to greyscale with: img_grey = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

like image 124
Salvador Dali Avatar answered Nov 04 '22 03:11

Salvador Dali


you should load your file like this

src.create(rows, cols, CV_8UC1);
src = imread(your-file, CV_8UC1);

and after that

adaptiveThreshold(src, dst, 255, ADAPTIVE_THRESH_GAUSSIAN_C, THRESH_BINARY, 75, 10);
like image 29
sam Avatar answered Nov 04 '22 03:11

sam


you can change the code to slightly like this :

img_blur = cv2.medianBlur(self.cropped_img,5).astype('uint8')
img_thresh_Gaussian = cv2.adaptiveThreshold(img_blur, 255, cv2.ADAPTIVE_THRESH_GAUSSIAN_C, cv2.THRESH_BINARY, 11, 2)

just by adding ('uint8') while blurring has resolved my issue.

like image 13
Vaibhav K Avatar answered Nov 04 '22 03:11

Vaibhav K


you have to imread your image in grayscale, so use the code below:

image = imread('address', 0)

0 exchange the channel of image to grayscale

like image 6
Aram.rt Avatar answered Nov 04 '22 04:11

Aram.rt