How to create a watermark on an image using OpenCV Python?

To add a watermark to an image, we will use the cv2.addWeighted() function from OpenCV. You can use the following steps to create a watermark on an input image −

Import the required library. In all the following Python examples, the required Python library is OpenCV. Make sure you have already installed it.

import cv2

Read the input image on which we are going to apply the watermark and read the watermark image.

img = cv2.imread("panda.jpg")
wm = cv2.imread("watermark.jpg")

Access the height and width of the input image, and the height, width of the watermark image.

h_img, w_img = img.shape[:2]
h_wm, w_wm = wm.shape[:2]

Calculate the coordinates of the center of the image. We are going to place the watermark at the center.

center_x = int(w_img/2)
center_y = int(h_img/2)

Calculate roi from top, bottom, right and left.

top_y = center_y - int(h_wm/2)
left_x = center_x - int(w_wm/2)
bottom_y = top_y + h_wm
right_x = left_x + w_wm

Add the watermark to the input image.

roi = img[top_y:bottom_y, left_x:right_x]
result = cv2.addWeighted(roi, 1, wm, 0.3, 0)
img[top_y:bottom_y, left_x:right_x] = result

Display the watermarked image. To display the image, we use cv2.imshow() function.

cv2.imshow("Watermarked Image", img)
cv2.waitKey(0)
cv2.destroyAllWindows()

Let's have a look at the example below for a better understanding.

We will use the following images as the Input Files in this program −

Example

In this Python program, we added a watermark to the input image.

# import required libraries
import cv2

# Read the image on which we are going to apply watermark
img = cv2.imread("panda.jpg")

# Read the watermark image
wm = cv2.imread("watermark.jpg")

# height and width of the watermark image
h_wm, w_wm = wm.shape[:2]

# height and width of the image
h_img, w_img = img.shape[:2]

# calculate coordinates of center of image
center_x = int(w_img/2)
center_y = int(h_img/2)

# calculate rio from top, bottom, right and left
top_y = center_y - int(h_wm/2)
left_x = center_x - int(w_wm/2)
bottom_y = top_y + h_wm
right_x = left_x + w_wm

# add watermark to the image
roi = img[top_y:bottom_y, left_x:right_x]
result = cv2.addWeighted(roi, 1, wm, 0.3, 0)
img[top_y:bottom_y, left_x:right_x] = result

# display watermarked image
cv2.imshow("Watermarked Image", img)
cv2.waitKey(0)
cv2.destroyAllWindows()

Output

On the execution of the above code, it will produce the following output window.