Hugin's align_image_stack
tool seems to be highly recommended for photos. It may well work in such cases where you have EXIF data, the images are all the same resolution and taken from roughly the same position.
However, what if I just have 2D transformations I'd like to align. No fancy "field of view", 3D position optimizations that expect the images to be of a 3D scene. Lets say I just have two images with identical content. The only difference is one has a margin or the other is cropped a little. Maybe one is a different resolution. At the extreme end, colours may have been changed slightly or there's a watermark/text in the way.
For example...
Is there a simple command line tool I can use to align these two images?
I'm using linux, but something cross platform would be great.
> align_image_stack -a out_ a.png b.png
Unable to read EXIF data from opened file:a.png
Unable to read EXIF data from opened file:b.png
Segmentation fault (core dumped)