Remove noise from threshold TEXT images in opencv

Question

I have these images:

I want to remove the noise from the background(i.e make the background white in 1st and 3rd and black in 2nd) in all these images, I tried this method: Remove noise from threshold image opencv python but it didn't work, how can I do it?

P.S This is the original image that I am trying to enhance.

You can try cleaning it up using erosion and dilation if you haven't done that yet — M Z, Aug 03 '20 at 14:36
Your question is not very clear. You show noisy images, but then you show your original image, which is already clean. Which images do you want to process - the 3 noisy ones or the 1 good one? — fmw42, Aug 03 '20 at 18:34
@fmw42 Actually I want to enhance the original image... i.e the handwriting should become dark(er) and the background pure white... I am doing this to train my ML model — WinterSoldier, Aug 03 '20 at 18:43

score 5 · Accepted Answer · edited Aug 04 '20 at 07:45

You can use adaptive threshold on your original image in Python/OpenCV

Input:

import cv2
import numpy as np

# read image
img = cv2.imread("writing.jpg")

# convert img to grayscale
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

# do adaptive threshold on gray image
thresh = cv2.adaptiveThreshold(gray, 255, cv2.ADAPTIVE_THRESH_MEAN_C, cv2.THRESH_BINARY, 21, 10)

# write results to disk
cv2.imwrite("writing_thresh.jpg", thresh)

# display it
cv2.imshow("thresh", thresh)
cv2.waitKey(0)
cv2.destroyAllWindows()

Result:

Remove noise from threshold TEXT images in opencv

1 Answers1