Why this is deliberately not AI
AI upscalers do produce impressive-looking results, and it is worth being clear about how: the model invents plausible detail that was never in your photograph. Textures, pores, letterforms — synthesised to look right, with no obligation to be right.
For decorative images that trade is often fine. For anything that carries information it is quietly dangerous: models have redrawn digits on number plates, reshaped faces in group photos and sharpened text into words that were never written. The output looks more trustworthy while being less true.
Lanczos resampling makes the opposite trade. Every new pixel is a weighted average of real neighbouring pixels — mathematically faithful, deterministic, identical on every run. The enlargement is honest about what the original contained, which is the property a document, product photo or evidence shot actually needs.
What enlargement can and cannot recover
Upscaling adds pixels, not information. Detail the camera captured spreads cleanly across the larger canvas; detail it never captured does not appear. A sharp 1000-pixel photo becomes a clean 4000-pixel print file — a blurred one becomes a bigger blur.
The sharpening pass matters more than it sounds. Pure interpolation is soft, because averaging is a smoothing operation; the calibrated unsharp step restores edge contrast the resampling spread out, which is recovering real structure, not inventing it.
Expect excellent results on logos, screenshots, documents and reasonably sharp photos, and honest mediocrity on images that were already soft or heavily compressed. The tool will not pretend otherwise, because the alternative is a fabricated picture.
Practical sizes for printing in India
Print needs around 150 to 300 pixels per inch. A passport-size print wants roughly 600×750 pixels, an A4 poster around 1750×2480 at the low end — so a 900-pixel web image needs 2× for A4 and a phone photo usually needs nothing at all.
For flex banners and hoardings the rules relax: viewing distance drops the requirement to 30–75 pixels per inch, so a 4× upscale of a decent photo covers a surprising amount of banner. Ask the printer for their target and arithmetic does the rest.
There is a ceiling: output beyond about 24 million pixels exceeds what browser canvases handle reliably, and the tool says so rather than crashing mid-way. For an image that large, 2× now and 2× again after a check is the workable route.