how to cut picture with circle mask that has alpha color?

Question

i have a problem where i need to go from this input:

First Input src1 = input2.png :

applying this src2 = input2.png as a mask:

to get this output:

I have tried to, but i didnt know how specifiy that the outer color is alpha color (completely transparent) i either endup with black or white.

src1 = cv2imread('input1.png')
src2 = cv2.imread('input2.png')

both same size

print(src2.dtype)
# uint8

dst = cv2.bitwise_and(src1, src2)

cv2.imwrite('res.jpg', dst)

please post the code you tried, to have something to work on — Alberto Sinigaglia, Mar 23 '22 at 22:44
@AlbertoSinigaglia this is the tutorial i followed https://note.nkmk.me/en/python-opencv-numpy-alpha-blend-mask/ — Oussama, Mar 23 '22 at 22:46
Please, post the code on the question, not a link to a page that one day might be taken down — Alberto Sinigaglia, Mar 23 '22 at 22:48
except from this, looks like that this https://stackoverflow.com/questions/61516526/how-to-use-opencv-to-crop-circular-image is what you are looking for — Alberto Sinigaglia, Mar 23 '22 at 22:48
@AlbertoSinigaglia yes i saw that question days ago but outer space of the circle is not alpha color. — Oussama, Mar 23 '22 at 22:53
Does this answer your question? [Using openCV to overlay transparent image onto another image](https://stackoverflow.com/questions/40895785/using-opencv-to-overlay-transparent-image-onto-another-image) — Christoph Rackwitz, Mar 24 '22 at 12:07
@ChristophRackwitz srry bro i missed this comment but it doesnt answer the question fmw42 posted the right answer. — Oussama, Mar 24 '22 at 13:56

score 3 · Accepted Answer · answered Mar 24 '22 at 01:06

Here is one way to do that in Python/OpenCV.

Just read the second image unchanged. Then copy the alpha channel from the second to the first image.

Image 1:

Image 2:

import cv2
import numpy as np

# read images
img1 = cv2.imread('picture1.png')
img2 = cv2.imread('picture2.png', cv2.IMREAD_UNCHANGED)

# copy alpha from second image to first image
result = img1.copy()
result = cv2.cvtColor(result, cv2.COLOR_BGR2BGRA)
result[:,:,3] = img2[:,:,3]

# save results
cv2.imwrite('picture1_circled.png', result)

Result:

how to cut picture with circle mask that has alpha color?

both same size

1 Answers1