Adaptive Threshold error: (-215:Assertion failed) src.type() == CV_8UC1 in function ‘adaptiveThreshold’

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We Are Going To Discuss About Adaptive Threshold error: (-215:Assertion failed) src.type() == CV_8UC1 in function ‘adaptiveThreshold’. So lets Start this Python Article.

Contents
  1. Adaptive Threshold error: (-215:Assertion failed) src.type() == CV_8UC1 in function 'adaptiveThreshold'
  2. Solution 1
  3. Solution 2
  4. Solution 3
  5. Conclusion

Adaptive Threshold error: (-215:Assertion failed) src.type() == CV_8UC1 in function ‘adaptiveThreshold’

  1. How to solve Adaptive Threshold error: (-215:Assertion failed) src.type() == CV_8UC1 in function 'adaptiveThreshold'

    The error says the solution: src.type() == CV_8UC1 meaning you need to set your image type to the uint8 source
    So if you redefine your img variable:
    img = image.img_to_array(img, dtype='uint8')
    Problem will be solved but I have a question.
    Why do you define the below statement?
    img_grey = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
    How do you know load_img loads the image in BGR fashion?
    We know opencv loads the image cv2.imread in BGR fashion.
    The statement is wrong, since load_img loads the image in RGB format source
    Therefore the correct statement will be:
    img_grey = cv2.cvtColor(img, cv2.COLOR_RGB2GRAY)
    or you can do:
    img = image.load_img('15f8U.png', grayscale=True, target_size=(224, 224))
    Correct Code:
    from keras.preprocessing import image import cv2 import matplotlib.pyplot as plt img = image.load_img('15f8U.png', grayscale=True, target_size=(224, 224)) img = image.img_to_array(img, dtype='uint8') print(img.shape) ## output : (224,224,3) #plt.imshow(img_grey) th3 = cv2.adaptiveThreshold(img,255,cv2.ADAPTIVE_THRESH_GAUSSIAN_C,cv2.THRESH_BINARY,11,2) plt.figure(figsize=(20,10)) plt.imshow(th3, cmap="gray") plt.show()

  2. Adaptive Threshold error: (-215:Assertion failed) src.type() == CV_8UC1 in function 'adaptiveThreshold'

    The error says the solution: src.type() == CV_8UC1 meaning you need to set your image type to the uint8 source
    So if you redefine your img variable:
    img = image.img_to_array(img, dtype='uint8')
    Problem will be solved but I have a question.
    Why do you define the below statement?
    img_grey = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
    How do you know load_img loads the image in BGR fashion?
    We know opencv loads the image cv2.imread in BGR fashion.
    The statement is wrong, since load_img loads the image in RGB format source
    Therefore the correct statement will be:
    img_grey = cv2.cvtColor(img, cv2.COLOR_RGB2GRAY)
    or you can do:
    img = image.load_img('15f8U.png', grayscale=True, target_size=(224, 224))
    Correct Code:
    from keras.preprocessing import image import cv2 import matplotlib.pyplot as plt img = image.load_img('15f8U.png', grayscale=True, target_size=(224, 224)) img = image.img_to_array(img, dtype='uint8') print(img.shape) ## output : (224,224,3) #plt.imshow(img_grey) th3 = cv2.adaptiveThreshold(img,255,cv2.ADAPTIVE_THRESH_GAUSSIAN_C,cv2.THRESH_BINARY,11,2) plt.figure(figsize=(20,10)) plt.imshow(th3, cmap="gray") plt.show()

Solution 1

The error says the solution: src.type() == CV_8UC1 meaning you need to set your image type to the uint8 source

So if you redefine your img variable:

img = image.img_to_array(img, dtype='uint8')

Problem will be solved but I have a question.

Why do you define the below statement?

img_grey = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

How do you know load_img loads the image in BGR fashion?

We know opencv loads the image cv2.imread in BGR fashion.

The statement is wrong, since load_img loads the image in RGB format source

Therefore the correct statement will be:

img_grey = cv2.cvtColor(img, cv2.COLOR_RGB2GRAY)

or you can do:

img = image.load_img('15f8U.png', grayscale=True, target_size=(224, 224))

Correct Code:

from keras.preprocessing import image
import cv2
import matplotlib.pyplot as plt

img = image.load_img('15f8U.png', grayscale=True, target_size=(224, 224))
img = image.img_to_array(img, dtype='uint8')

print(img.shape)
## output : (224,224,3)
#plt.imshow(img_grey)

th3 = cv2.adaptiveThreshold(img,255,cv2.ADAPTIVE_THRESH_GAUSSIAN_C,cv2.THRESH_BINARY,11,2)
plt.figure(figsize=(20,10))
plt.imshow(th3, cmap="gray")
plt.show()

Original Author Ahx Of This Content

Solution 2

cv2.adaptive_threshold needs an input array of dtype uint8:

img_grey = img_grey.astype(np.uint8)

th3 = cv2.adaptiveThreshold(img_grey...

Original Author Nicolas Gervais Of This Content

Solution 3

@bakuriu thresholding works on grayscaled images only, you need to convert the image to grayscale first and the the adaptiveThreshold



img = image.img_to_array(img2, dtype='uint8')
img_grey = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
th3 = cv2.adaptiveThreshold(img_grey,255,cv2.ADAPTIVE_THRESH_GAUSSIAN_C,cv2.THRESH_BINARY,11,2)

Original Author Swati Pandey Of This Content

Conclusion

So This is all About This Tutorial. Hope This Tutorial Helped You. Thank You.

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I am an Information Technology Engineer. I have Completed my MCA And I have 4 Year Plus Experience, I am a web developer with knowledge of multiple back-end platforms Like PHP, Node.js, Python and frontend JavaScript frameworks Like Angular, React, and Vue.

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