In whatsis wrote:
I’ve got a number of jpg’s like 300×400 dpi and would like to resize them to 800×600 viewing. Have any tips on preserving or restoring the quality?
Yep!
Step 1: Forget it.
Step 2: Understand that enlarging a pixel based image always loses quality. Always. No program, no technique, no algorithm is capable of enlarging a pixel image and creating detail that is not in the original.
Forget Hollywood, forget "Blade Runner," forget the breathless marketing hype of programs like Geniune Fractals. It can not be done; it is not even theoretically possible.
You’ll get results that suck a bit less if you use "stair interpolation"– sizing it up repeatedly in small increments–but you will never get results that look better than the original.