Transparet pixels are being pasted as black in PIL

Question

I paste an image with transparent pixels, but they are black in the final image

img = Image.new('RGBA', (100, 100), "white")

arbol16 = Image.open("arbol16.png")

img.paste(arbol16,( 0, 0, 16, 16))

img.show()

arbol16.png image file:

Answer 1

I think you're (understandably) being confused by what the img.show() is displaying — which I believe is wrong (and may in fact be a bug). On my Windows system a temporary .BMP image is displayed, and it looks like the transparent pixels are black.

However if you add a line like img.save('arbol16_mod.png') at the end and then view that image file by manually opening it in some image file viewing program, such as Paint, Windows Photo Viewer, or Photoshop, the result is correct.

Answer 2

The paste method does not take into account the alpha of the image it's pasting; you need to add a mask parameter to control that. If the image you're pasting is RGBA you can just pass it twice.

arbol16 = arbol16.convert("RGBA")
img.paste(arbol16, (0, 0, 16, 16), arbol16)