autocrop

#!/usr/bin/env python3
import argparse
from PIL import Image, ImageColor

helpmsg = "Automatically crop border from image"
parser = argparse.ArgumentParser(description=helpmsg)
parser.add_argument('--color', '-c', type=ImageColor.getrgb,
        default=[255]*3, help="color to remove around subject")
parser.add_argument('--verbose', '-v', action='store_true')
parser.add_argument('filename', nargs='+', help="Images to crop")

args = parser.parse_args()

import numpy as np
import os

color3 = np.array(args.color, dtype=np.uint8)
for filename in args.filename:
    im = Image.open(filename)
    im = im.convert(mode='RGB')
    pixels = np.asarray(im)

    imshape = pixels.shape[:2]

    subject = (pixels != color3).all(axis=-1)

    left = subject.any(axis=0).argmax()
    up = subject.any(axis=1).argmax()

    subject = np.flip(subject) # flips all axes

    right = imshape[1] - subject.any(axis=0).argmax()
    down = imshape[0] - subject.any(axis=1).argmax()

    if args.verbose:
        print(f'upper left corner: {left}, {up}')
        print(f'lower right corner: {right}, {down}')
        print(f'image dims (HxW): {down-up} x {right-left}')

    pixels = pixels[up:down,left:right,:]
    im = Image.fromarray(pixels, mode="RGB")
    basename = os.path.splitext(filename)[0]
    outname = basename + '_cropped.png'
    im.save(outname)