Note: it's best if you choose an even number divisible by three)
How does this program work?
It's based on using a square part of an image, and appending rotated versions successively to construct finer and finer approximations to the Golden rectangle.
If you save the sample image above to your local machine, browse to it to load it, and use 610 as the width, with Rotate original image by 270, then you'll recreate the sample image (the hard way!). Then you can compare and contrast the results using different angles, the special effects, etc.