: Sorry, but what you ask there is impossible unless you can come up with a new image algorithm, as there is NO algorithm that can do that cleanly for every resolution out there. Blur is created any time you have to resize an image to a bigger image, as all algorithms guess at what the missing pixels are, and the guesses can be wrong. So unless someone creates a better math algorithm that is not possible.
For other engines, they are probably doing something else but the laws of image resizing say that is not possible. No algorithm does exist that can take a native 640 x 480 game and make it fit all resolutions out there, period.
What most AAA games do is they make the items individually for each and every resolution. You can do that too, make a version for each resolution out there, but even then they will miss a resolution here and there no matter what you do.