Transparent overlays with Python OpenCV
In this article, we are going to see how to Transparent overlays with Python OpenCV.
For this program to work, first we’ll need two inputs: Background Image, Overlay Image. We’ll then create a NumPy array with the same dimension as the background image, with all values as 0. Then we’ll create a mask using this array and the overlay.
Now the main part of our program the overlay will be done by using the cv2.addWeighted() method.
cv2.addWeighted() :This method basically calculates the average weighted sum of the two input arrays to return an output array.
Image can be downloaded from here: Beginnerlogo, Background
Below is the Implementation:
Python3
import cv2import numpy as np# Loading our images# Background/Input imagebackground = cv2.imread('Assets/img1.jpg') # Overlay imageoverlay_image = cv2.imread('Assets/overlay3.png') # Resize the overlay image to match the bg image dimensionsoverlay_image = cv2.resize(overlay_image, (1000, 1000))h, w = overlay_image.shape[:2]# Create a new np arrayshapes = np.zeros_like(background, np.uint8)# Put the overlay at the bottom-right cornershapes[background.shape[0]-h:, background.shape[1]-w:] = overlay_image# Change this into bool to use it as maskmask = shapes.astype(bool)# We'll create a loop to change the alpha# value i.e transparency of the overlayfor alpha in np.arange(0, 1.1, 0.1)[::-1]: # Create a copy of the image to work with bg_img = background.copy() # Create the overlay bg_img[mask] = cv2.addWeighted(bg_img, 1 - alpha, shapes, alpha, 0)[mask] # print the alpha value on the image cv2.putText(bg_img, f'Alpha: {round(alpha,1)}', (50, 200), cv2.FONT_HERSHEY_PLAIN, 8, (200, 200, 200), 7) # resize the image before displaying bg_img = cv2.resize(bg_img, (630, 630)) cv2.imshow('Final Overlay', bg_img) cv2.waitKey(0) |
Output: