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diff --git a/montage_images.py b/montage_images.py
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+#!/usr/bin/env python3
+#
+# Aaron LI
+# Created: 2016-05-08
+# Updated: 2016-05-08
+#
+
+"""
+Make a montage of the input 4 images by utilizing the `montage`
+tool from `ImageMagick`.
+
+Montage:
++----------+----------+
+|          |          |
+|  image1  |  image2  |
+|          |          |
++----------+----------+
+|          |          |
+|  image3  |  image4  |
+|          |          |
++----------+----------+
+
+Note:
+The resolution/dimension of the `image1` is taken as the reference, and
+the other 3 images are re-sized to match it in order to make an compact
+and grid-aligned montage.
+
+
+Credits:
+[1] ImageMagick v6 Examples -- Montage, Arrays of Images
+    https://www.imagemagick.org/Usage/montage/
+[2] ImageMagick montage: Resizing only one input image
+    https://stackoverflow.com/a/26273173/4856091
+"""
+
+
+import subprocess
+import argparse
+
+
+def get_image_size(image):
+    """
+    Get the size (dimension) of the image by utilizing `identify`.
+    """
+    results = subprocess.run(["identify", "-ping", "-format", "%w %h", image],
+                             check=True, stdout=subprocess.PIPE)
+    width, height = map(int, results.stdout.decode("utf-8").split())
+    return (width, height)
+
+
+def montage_images(infiles, outfile):
+    """
+    Combine the 4 input images to make a montage by utilizing `montage`.
+    """
+    img1, img2, img3, img4 = infiles
+    # `img1` is taken as the reference image (top-left)
+    w_ref, h_ref = get_image_size(img1)
+    w_img2, h_img2 = get_image_size(img2)
+    w_img3, h_img3 = get_image_size(img3)
+    # `img2` is re-sized to have the same height as `img1` (top-right)
+    ratio_img2 = h_ref / h_img2
+    W_img2, H_img2 = int(w_img2*ratio_img2), int(h_img2*ratio_img2)
+    # `img3` is re-sized to match the width of `img1` (bottom-left)
+    ratio_img3 = w_ref / w_img3
+    W_img3, H_img3 = int(w_img3*ratio_img3), int(h_img3*ratio_img3)
+    # `img4` is simply re-sized to fill the bottom-right area
+    W_img4, H_img4 = W_img2, H_img3
+    subprocess.run(args=[
+        "montage", img1,
+        "(", img2, "-resize", "%dx%d" % (W_img2, H_img2), ")",
+        "(", img3, "-resize", "%dx%d" % (W_img3, H_img3), ")",
+        "(", img4, "-resize", "%dx%d" % (W_img4, H_img4), ")",
+        "-geometry", "+1+1", "-tile", "2x2", outfile,
+    ])
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        description="Make a montage of the input 4 images")
+    parser.add_argument("-o", "--outfile", dest="outfile", required=True,
+                        help="output filename of the montage image")
+    parser.add_argument("images", nargs=4,
+                        help="filenames of 4 input images")
+    args = parser.parse_args()
+
+    montage_images(infiles=args.images, outfile=args.outfile)
+
+
+if __name__ == "__main__":
+    main()