How to resize an image to fit in the browser window?

Question

This seems trivial but after all the research and coding I can\'t get it to work. Conditions are:

1. The browser window size is unknown. So please don\'t propose

Answer 1

Building upon @Rohit's answer, this fixes issues flagged by Chrome, reliably resizes the images, and also works for multiple images that are vertically stacked, e.g.

There is probably a more elegant way of doing this.