State of the art in upsizing algorithms?

Started Jun 9, 2014 | Discussions thread
hjulenissen Senior Member • Posts: 2,269
Re: State of the art in upsizing algorithms ?

Nicolas Robidoux wrote:

Note that the "original" kitchen test image used for the above examples was sharpened. Enlarging sharpened images brings up issues that are not otherwise present.

Is "sharpened" (in this context) similar to "aliased" or "non-Nyquist"? Screen shots of text may be high contrast and various degrees of aliasing (see image linked below)

http://www.joelonsoftware.com/items/2007/06/12.html

It seems that font designers/text renderers have different philosohpy when it comes to trading position, weight, contrast etc in downsampling a high-resolution vectoried prototype to a low-resolution pixelized output. One might say that they use different filtering strategies (often hand-tuning one a letter-by-letter basis).

If sharpening was a simple high-pass filter with no clipping, then it would be an invertible function, and image scaling ought to tolerate it, right? But sharpening is common signal-dependent, and high-contrast edges will often be clipped into aliasing.

For something like a "vector-like" mosaic, it would seem like the original scene lends itself to non-linear edge-tracking algorithms, where "smooth & sharp" edges are more important than low-level textures?

-h

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