How can I retain background after dilating text in image

Question

import cv2
import numpy as np

# Load image, grayscale, Gaussian blur, Otsu's threshold
image = cv2.imread('1.png')
gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
blur = cv2.GaussianBlur(gray, (7,7), 0)
thresh = cv2.threshold(blur, 0, 255, cv2.THRESH_BINARY_INV + cv2.THRESH_OTSU)[1]

# Create rectangular structuring element and dilate
kernel = cv2.getStructuringElement(cv2.MORPH_RECT, (5,5))
dilate = cv2.dilate(thresh, kernel, iterations=4)


cv2.imshow('dilate', dilate)

cv2.waitKey()

I am trying to mask the text elements in an image and return an image with just the remaining portions. I have applied thresholding and dilating, but how can I retain the background.

Image after thresholding and dilating

Original image:

Answer 1

Here is a simple approach:

Using the inverted dilated image cv2.bitwise_not(dilate), create a mask over the original image.

res = cv2.bitwise_and(image, image, mask=cv2.bitwise_not(dilate))

In the above image you have all text regions and its boundaries masked out.

Now replace those masked out regions with the background of your original image. To do that, first I noted down the coordinates where of the text regoins in mask_ind. Then replaced the pixel values in those regions with the background of the original image image[0,0]

mask_ind = (dilate == 255)
res[mask_ind] = image[0,0]
cv2.imshow(res)