Another application of the problem explained in the article “Discovering a small image inside a large image using Python and OpenCV” is that you can use this code to find a special sign in a ID card Scan and make certain changes based on that.

For example, here we have given the program a type of sample certificate that has been scanned in reverse, and after finding the sign in the upper right corner of the card, we rotate it as many times as necessary to show the certificate image in the right direction.

Sample code:

import cv2

def find_image_in_larger_image(small_image, large_image):

# Read images

# Check if images are loaded successfully

if small_image is None or large_image is None:

print(“Error: Unable to load images.”)

return None

# Get dimensions of both images

small_height, small_width = small_image.shape

large_height, large_width = large_image.shape

# Find the template (small image) within the larger image

result = cv2.matchTemplate(large_image, small_image, cv2.TM_CCOEFF_NORMED)

# Define a threshold to consider a match

threshold = 0.6

# Find locations where the correlation coefficient is greater than the threshold

locations = cv2.findNonZero((result >= threshold).astype(int))

# If no match is found

if locations is None:

return None

# Determine the position of the matched areas

matched_positions = []

for loc in locations:

x, y = loc[0]

if x < large_width / 2:

position_x = “left”

otherwise:

position_x = “right”

if y < large_height / 2:

position_y = “top”

otherwise:

position_y = “bottom”

matched_positions.append((position_x, position_y))

return matched_positions

# Example usage

small_image_path = “mark.jpg”

large_image_path = “card.jpg”

small_image = cv2.imread(small_image_path, cv2.IMREAD_GRAYSCALE)

large_image = cv2.imread(large_image_path, cv2.IMREAD_GRAYSCALE)

rotated_large_image=large_image

positions = find_image_in_larger_image(small_image, large_image)

max_rotation = 10 # Set the maximum rotation limit

if positions:

position_x, position_y = positions[0]

print(“Position: {}, {}”.format(position_x, position_y))

while max_rotation>0:

max_rotation-=1

rotated_large_image = cv2.rotate(rotated_large_image, cv2.ROTATE_90_CLOCKWISE)

positions = find_image_in_larger_image(small_image, rotated_large_image)

if positions:

position_x, position_y = positions[0]

print(“Position: {}, {}”.format(position_x, position_y))

if(position_x==’right’ and position_y==’top’):

cv2.imshow(“Mark”, small_image)

cv2.imshow(“Original”, large_image)

cv2.imshow(“Result”, rotated_large_image)

cv2.waitKey(0)

cv2.destroyAllWindows()

max_rotation=0

otherwise:

print(“No match found after {} rotations.”.format(10-max_rotation))

otherwise:

print(“No match found after {} rotations.”.format(10-max_rotation))

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