How to crop from one image and paste into another with PIL?

A PIL crop box is defined as a 4-tuple of pixel coordinates: (left, upper, right, lower).

To fix your code to get a 30x30 crop:

box = (70, 70, 100, 100)

Broken down into components:

x, y, w, h = (70, 70, 30, 30)
box = (x, y, x + w, y + h)

For future visitors: this error may also come up if the box argument to paste contains floats instead of ints.