import numpy as np
import cv2
import matplotlib.pyplot as plt
 
path = 'frame_00003_rgb.png'
img = cv2.imread(path)
img1 = np.zeros([480, 640, 5])
img1[:, :, 0:3] = np.array(img)
 
cv2.imshow('test1', np.array(img)[:,:,2])
cv2.imshow('test2', img1[:, :, 0])
cv2.waitKey(10000)

import numpy as np
import cv2
import matplotlib.pyplot as plt
 
path = 'frame_00003_rgb.png'
img = cv2.imread(path)
img1 = np.zeros([480, 640, 5], dtype=np.uint8)
img1[:, :, 0:3] = np.array(img)
 
cv2.imshow('test1', np.array(img)[:,:,2])
cv2.imshow('test2', img1[:, :, 0])
cv2.waitKey(10000)

# pip install Pillow
import PIL.Image as Image
# 以第一个像素为准，相同色改为透明
def transparent_back(img):
  img = img.convert('RGBA')
  L, H = img.size
  color_0 = (255,255,255,255)#要替换的颜色
  for h in range(H):
    for l in range(L):
      dot = (l,h)
      color_1 = img.getpixel(dot)
      if color_1 == color_0:
        color_1 = color_1[:-1] + (0,)
        img.putpixel(dot,color_1)
  return img
if __name__ == '__main__':
  img=Image.open('img.png')
  img=transparent_back(img)
  img.save('img2.png')