Image Upscaler

What upscaling can and cannot recover

This is worth being clear about first. An image only contains the detail it was saved with, and no tool invents information that was never captured. What upscaling does is enlarge the image while filling the new pixels intelligently, so edges stay smooth instead of turning into visible squares. A slightly small photo becomes usable at a larger size. A tiny, heavily compressed thumbnail will come out bigger and still soft, because there was nothing there to work with.

Why simple enlarging looks so bad

When you stretch an image without any processing, each original pixel becomes a block of identical pixels. That is why a scaled up photo looks like a mosaic. Smooth scaling instead calculates each new pixel from the ones around it, so gradients and edges continue naturally rather than stepping. The result is not sharper than the original, but it looks far more natural at the larger size.

Getting the most out of it

• Start from the largest original you have, not a copy already resized down.
• Prefer a PNG source over a JPG, since JPG has already discarded detail.
• 2x is reliable on most images. 4x works best on subjects with soft edges rather than fine text.
• For printing, enlarge less than you think you need and check at full size before committing.