12. ImageFilter Find Edges

See: https://pillow.readthedocs.io/en/stable/reference/ImageFilter.html#filters

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12.1. Find Edges

Use the Image.filter(ImageFilter.FIND_EDGES) method to find the edges of parts of the image.

Best results require an image in RGB mode rather than RGBA.

from PIL import Image, ImageFilter

with Image.open("test_images/alph_blocks.png") as im:
    im_rgb = im.convert(mode='RGB')
    new_im = im_rgb.filter(ImageFilter.FIND_EDGES)
    new_im.save("filters/find_edges.png")