How to align a list of 2D images?

I have a series of 2D, grayscale images of different sizes (they are extracted silhouettes of the same person). I would like to be able to align them all, so that all images are the same size.

The transformations I would like to use are only: scaling, and translation. I'm trying to use OpenCV with cv2.estimateRigidTransform, but it also introduces rotations.

Two sample images are the following: enter image description here enter image description here

How many English words
do you know?
Test your English vocabulary size, and measure
how many words do you know
Online Test
Powered by Examplum