Convert White Pixels to Black in OpenCV python

Question

I am trying to convert the white background of the input image into black using python OpenCV.But all the white pixels are not completely getting converted to black. I have attached the input and output images.

Input Image :

Output Image:

I have used the following code for conversion:

img[np.where((img==[255,255,255]).all(axis=2))] = [0,0,0];

What should I do?

Answer 1

I know this has already been answered. I have a coded python solution for you.

Firstly I found this thread explaining how to remove white pixels.

The Result:

Another Test img:

Edit This is a way better and shorter method. I looked into it after @ZdaR commented on looping over an images matrix.

[Updated Code]

img = cv2.imread("Images/test.pnt")

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

ret, thresh = cv2.threshold(gray, 240, 255, cv2.THRESH_BINARY)

img[thresh == 255] = 0

kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (5, 5))
erosion = cv2.erode(img, kernel, iterations = 1)

cv2.namedWindow('image', cv2.WINDOW_NORMAL)
cv2.imshow("image", erosion)
cv2.waitKey(0)
cv2.destroyAllWindows()

Source

[Old Code]

img = cv2.imread("Images/test.png")

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

ret, thresh = cv2.threshold(gray, 240, 255, cv2.THRESH_BINARY)

white_px = np.asarray([255, 255, 255])
black_px = np.asarray([0, 0, 0])

(row, col) = thresh.shape
img_array = np.array(img)

for r in range(row):
    for c in range(col):
        px = thresh[r][c]
        if all(px == white_px):
            img_array[r][c] = black_px

kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (5, 5))
erosion = cv2.erode(img_array, kernel, iterations = 1)

cv2.namedWindow('image', cv2.WINDOW_NORMAL)
cv2.imshow("image", erosion)
cv2.waitKey(0)
cv2.destroyAllWindows()

Other Sources used: OpenCV Morphological Transformations