Converting Image from RGBA to RGB reveals padding, how to crop that?

I'm trying to convert an image from RGBA to RGB. But the conversion to RGB is adding padding to the image. How can I convert without the padding? Or how can I remove it?

    img = Image.open('path.png')
    img.save("img.png")
    
    rgb_im = img.convert('RGB')
    rgb_im.save("rgb_im.png")

Thank you. Images below, before and after conversion:

enter image description here

enter image description here

1 answer

  • answered 2022-05-04 11:41 David

    If you open your first image, you'll see that the canvas is larger than the visible image, as you have a transparent frame represented by pixels having rgba=(255,255,255,0). When you remove the alpha channel by converting RGBA to RGB, that transparency disappear, as only rgba=(255,255,255) remains, which turns out to be the white you see in the second image.

    So you want to make something similar to what's suggested here

    from PIL import Image, ImageChops
    
    def trim_and_convert(im):
        bg = Image.new(im.mode, im.size, (255,255,255,0))
        diff = ImageChops.difference(im, bg)
        diff = ImageChops.add(diff, diff, 2.0, -100)
        bbox = diff.getbbox()
        if bbox:
            return im.crop(bbox).convert('RGB')
    
    im = Image.open("path.png")
    
    rgb_im = trim_and_convert(im)
    rgb_im.save("rgb_im.png")
    

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