[FIXED] Remove stamp from bill python

Issue

Any ideas on how to remove the stamp from this bill prior to OCR processing?

Solution

Here is one way to do that in Python/OpenCV.

• Read input
• Threshold on yellow
• Dilate to fill out rectangle
• Get largest contour
• Draw a white filled contour on the input image
• Save the results

Input:

import cv2
import numpy as np

# read image
img = cv2.imread('form_with_label.jpg')

# threshold on yellow
lower=(0,200,200)
upper=(100,255,255)
thresh = cv2.inRange(img, lower, upper)

# apply dilate morphology
kernel = np.ones((9,9), np.uint8)
mask = cv2.morphologyEx(thresh, cv2.MORPH_DILATE, kernel)

# get largest contour
contours = cv2.findContours(mask, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
contours = contours[0] if len(contours) == 2 else contours[1]
big_contour = max(contours, key=cv2.contourArea)
x,y,w,h = cv2.boundingRect(big_contour)

# draw filled white contour on input 
result = img.copy()
cv2.drawContours(result,[big_contour],0,(255,255,255),-1)

# save cropped image
cv2.imwrite('form_with_label_thresh.png',thresh)
cv2.imwrite('form_with_label_mask.png',mask)
cv2.imwrite('form_with_label_removed.png',result)

# show the images
cv2.imshow("THRESH", thresh)
cv2.imshow("MASK", mask)
cv2.imshow("RESULT", result)
cv2.waitKey(0)
cv2.destroyAllWindows()

Thresholded Image:

Morphology Dilated Image:

Result:

Answered By - fmw42