Calculate the minimal bounding box of a series of images.

find_bounding_box.py

#!/usr/bin/env python
"""Calculate the minimal bounding box of a series of images.

Example usage::

    $ find_bounding_box.py *.jpg
    836x680+64+0
    $ mogrify -crop 836x680+64+0 *.jpg
    
Requires the `identify` command which is part of ImageMagick.
"""
from __future__ import print_function

import re
import subprocess
import sys

_bbox_match = re.compile(r'^(\d+)x(\d+)\+(\d+)\+(\d+)$').match

def bounding_box(fname):
    """Calculate the bounding box of a file."""
    box = subprocess.check_output(['identify', '-format', '%@', fname])
    w, h, x, y = map(int, _bbox_match(box).groups())
    return w, h, x, y

def minimal_bounding_box(fnames):
    """Calculate the minimal bounding box of a sequence of files."""
    x0 = []
    y0 = []
    x1 = []
    y1 = []

    for fname in fnames:
        w, h, x, y = bounding_box(fname)

        x0.append(x)
        y0.append(y)
        x1.append(w+x)
        y1.append(h+y)

    x0 = min(x0)
    x1 = max(x1)
    y0 = min(y0)
    y1 = max(y1)

    x = x0
    w = x1-x0
    y = y0
    h = y1-y0

    return w, h, x, y

if __name__ == "__main__":

    if len(sys.argv) == 1:
        print("Usage: %s <FILE...>" % sys.argv[0], file=sys.stderr)
        sys.exit(1)
    w, h, x, y = minimal_bounding_box(sys.argv[1:])

    print('%dx%d+%d+%d' % (w, h, x, y))