How to merge a transparent png image with another image using PIL

Question

I have a transparent png image "foo.png" and I've opened another image with

im = Image.open("foo2.png"); 

now what i need is to merge foo.png with foo2.png.

( foo.png contains some text and I want to print that text on foo2.png )

Answer 1

from PIL import Image  background = Image.open("test1.png") foreground = Image.open("test2.png")  background.paste(foreground, (0, 0), foreground) background.show() 

First parameter to .paste() is the image to paste. Second are coordinates, and the secret sauce is the third parameter. It indicates a mask that will be used to paste the image. If you pass a image with transparency, then the alpha channel is used as mask.

Check the docs.

Answer 2

Image.paste does not work as expected when the background image also contains transparency. You need to use real Alpha Compositing.

Pillow 2.0 contains an alpha_composite function that does this.

background = Image.open("test1.png") foreground = Image.open("test2.png")  Image.alpha_composite(background, foreground).save("test3.png") 

EDIT: Both images need to be of the type RGBA. So you need to call convert('RGBA') if they are paletted, etc.. If the background does not have an alpha channel, then you can use the regular paste method (which should be faster).