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scaling algorithms for simple multiples--question?

267 Views 1 Reply 2 Participants Last post by lwang, Nov 21, 2002

rlsmith

Discussion Starter · Nov 20, 2002

I have a question for those who know about scaling algorithms.

Occasionally (but not often) a scaling situation calls for simple multiples. An example is the new Sanyo Z1 projector, which has height and width specs that are each exactly 1/2 of 1080X1920. This means that each pixel of the display will associate with a 4-pixel box of the source data.

The question is: is the best algorithm in such a case just to average together the four pixels, or is there a better algorithm?

Analogously, when upscaling by simple multiples, do you just make (say) 4 copies of a source pixel, or is there a better algorithm? [One example would be upscaling an SVGA source into a UXGA display, which is exactly twice as big in each dimension.]

Thanks.

Bob

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lwang

· #2 · Nov 21, 2002

Real cheap scalers does a pixel copy horizontally and vertically.

X

XXXXXX

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becomes

X

X

XXXXXX

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Nex step would do a linear interpolation between the pixels. Something like (when only doing vertical scaling):

X

XXXXXX

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becomes

X

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XXXXXXX

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More advanced algorithm does various higher order interpolation (cubic, bi-cubic, etc) and creates a less staggered image:

X

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becomes

X

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XXXXXXX

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This results in a closer approximation to a curve.

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