Converting grayscale png with transparency using PIL

Question

PIL corrupt png images with transparency if i make them grayscale. Why?

Here's my code:

input = Image.open('input.png')
output = ImageOps.grayscale(input)
output.save('output.png', **input.info)

Input

Output

is there a way to fix that?

Answer 1

You can use convert method with luminance trick:

Image.open('input.png').convert('LA').save('output.png')