Strategy for resizing images stepwise for best quality

[mosbth]

Resize the image in small steps, instead of one step. Smaller steps will, most likely, result in a better end result. If an image is 1600px wide and target is 100px, then start by resizing to 400px and then to 100px. 4px to 1px steps.

Make this strategy default behaviour, with an option to make only one resize.