I wanted to overlay one image over another dynamic开发者_JAVA百科ally using a Python library, and was wondering which one would be easy to use.

Thanks for your help!

If you want to overlay two images, simply use the OpenCV libraries.

[Sample]

import cv2
import numpy as np

def overlay(image1, image2, x, y):
    image1_gray = cv2.cvtColor(image1, cv2.COLOR_BGR2GRAY)
    _, contours, _ = cv2.findContours(image1_gray, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)
    image1_mask = np.zeros_like(image1)
    cv2.drawContours(image1_mask, contours, -1, (255,255,255), -1)
    idx = np.where(image1_mask == 255)
    image2[y+idx[0], x+idx[1], idx[2]] = image1[idx[0], idx[1], idx[2]]
    return image2

if __name__ == '__main__':
    grass_img = cv2.imread('grassland.jpg')
    horse_img = cv2.imread('horse.png')
    overlayed = overlay(horse_img, grass_img, 300, 300)
    cv2.imwrite('overlayed.png', overlayed)

The result image was resized to reduce its volume, but in the above code, the resize code was omitted.

Result:

Update!

Here is the code using image's alpha value, and the output is better than before.

The idea is from overlay a smaller image on a larger image python OpenCv

def better_overlay(image1, image2, x, y):
    image1_alpha = image1[:, :, 3] / 255.0
    height, width = image1.shape[0], image1.shape[1]
    for c in range(3):
        image2[y:y+height, x:x+width, c] = image1_alpha * image1[:, :, c] + (1.0 - image1_alpha)* image2[y:y+height, x:x+width, c]
    return image2

Result:

Usually PIL(Python Imaging Library) is for image processing stuff.