18. ImageFilter RankFilter

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

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18.1. RankFilter

Use the Image.filter(ImageFilter.RankFilter(size, rank)) method to use the chosen rank of pixel values in a pixel area given by the size.

The rank filter sorts all pixels in a window of the given size, and returns the rank’th value.

size - The kernel size, in pixels.

rank - What pixel value to pick. Use 0 for a min filter, size * size / 2 for a median filter, size * size - 1 for a max filter, etc.

from PIL import Image, ImageFilter


with Image.open("test_images/river_valley.jpg") as im:
    new_im = im.filter(ImageFilter.RankFilter(size=3, rank=1))
    new_im.save("filters/RankFilter1.png")
    new_im = im.filter(ImageFilter.RankFilter(size=3, rank=2))
    new_im.save("filters/RankFilter2.png")