问题
I want to make an inverse filled rectangle in this picture.
The code I have:
import cv2
lena = cv2.imread('lena.png')
output = lena.copy()
cv2.rectangle(lena, (100, 100), (200, 200), (0, 0, 255), -1)
cv2.addWeighted(lena, 0.5, output, 1 - .5, 0, output)
cv2.imshow('', output)
What I want:
回答1:
Here's what I would do:
# initialize output
output = np.zeros_like(lena, dtype=np.uint8)
output[:,:,-1] = 255
# this is your box top_x
tx,ly,bx,ry = 100,100,200,200
# copy lena to output
output[tx:bx,ly:ry] = lena[tx:bx,ly:ry]
cv2.addWeighted(lena, 0.5, output, 1 - .5, 0, output);
OUtput:
回答2:
Here is another way to do it in Python/OpenCV. Though it is not as elegant as the solution from Quang Hoang.
- Read the input
- Create a red image of the same size
- Blend the red image with the input
- Create a white image with a black rectangle for the "hole"
- Combine the blended image and the original image using the mask
- Save the result
Input:
import cv2
import numpy as np
# read image
img = cv2.imread('lena.jpg')
# create red image
red = np.full_like(img,(0,0,255))
# add red to img and save as new image
blend = 0.5
img_red = cv2.addWeighted(img, blend, red, 1-blend, 0)
# create white image for mask base
mask = np.full_like(img, (1,1,1), dtype=np.float32)
# define rectangle for "hole" and draw as black filled on the white base mask
x1,y1,x2,y2 = 100,100,200,200
mask = cv2.rectangle(mask, (x1, y1), (x2, y2), (0, 0, 0), -1)
# combine img and img_red using mask
result = cv2.add(img*(1-mask),img_red*mask).astype(np.uint8)
cv2.imshow('img', img)
cv2.imshow('red', red)
cv2.imshow('img_red', img_red)
cv2.imshow('mask', mask)
cv2.imshow('result', result)
cv2.waitKey(0)
cv2.destroyAllWindows()
# save results
cv2.imwrite('lena_hole_mask.jpg', (255*mask).astype(np.uint8))
cv2.imwrite('lena_plus_red.jpg', result)
Mask:
Result:
来源：https://stackoverflow.com/questions/60456616/how-do-i-make-an-inverse-filled-transparent-rectangle-with-opencv