Python PIL: Blend transparent image onto another

Question

I need to blend an image over another image using Pythons PIL Library.

As you can see in the image below, my two source images are A and B. When I do:

imageA.paste(imageB, (0, 0), imageB)

I get C as a result, but the part at the top of the gray background is now transparent. Image D is what I get when I put B over A in Photoshop and is what I need to achieve with PIL.

What am I doing wrong? How can I compose B over A in PIL to get D instead of C?

Example Image

what happens with: `imageA.paste(imageB, (0, 0), mask=imageB)` — RickyA, Jul 03 '14 at 09:15
@RickyA That should be exactly the same: the third argument to `paste` *is* the mask. Try using `imageA` as the mask instead: `imageA.paste(imageB, (0, 0), imageA)` — Germano, Jul 03 '14 at 09:30
@Germano: That doesn't work either, image B has a drop shadow that would be cut off if I do that. — Daniela, Jul 03 '14 at 10:46
Don't use PIL, use Pillow. See http://stackoverflow.com/a/15919897/5987 — Mark Ransom, Jul 03 '14 at 14:48
I can't reproduce this problem. When I run `imageA.paste(imageB, (0, 0), imageB)` on some test png files it produces something similar to D. Could you post your source images (A & B) along with your full code? — Peter Gibson, Oct 14 '14 at 06:09
What modes are the source and mask in ? Try to have them in RGBA mode for blending. — , Nov 19 '14 at 09:58
Possible duplicate of http://stackoverflow.com/questions/5324647/how-to-merge-a-transparent-png-image-with-another-image-using-pil — Charles Merriam, Aug 24 '15 at 01:28

score 3 · Answer 1 · answered Dec 17 '15 at 01:24

3

use RGBA for transparency mask

imageA.paste(imageB, (0, 0), imageB.convert('RGBA'))

answered Dec 17 '15 at 01:24

autopython

41
4

Thank you! This is the best solution! The third parameter is a transparency map, but instead of creating it manually you just created it with PIL. This should be the accepted answer. – gempir Aug 03 '20 at 10:00

score 1 · Answer 2 · edited May 23 '17 at 10:32

I can't comment for now (rep constraint).

But I think what you really need, according to your need, is to do this instead:

imageB.paste(imageA, (0, 0), imageA)

Basically, that is, make B the background image to get the desired results, because that's what I see in D.

EDIT: Looking around more, I found this: https://stackoverflow.com/a/15919897/4029893

I think you should definitely use the alpha_composite method, since paste doesn't work as expected for background images with transparency.

Python PIL: Blend transparent image onto another

2 Answers2