Digital BW, The Print

> From: Jeff Medkeff
>
> Stair interpolation refers to iteratively computing a spline over and
> over again, usually in fixed proportions, until you get the output size
> you want. For example, if you used bicubic interpolation and increased
> the file size by 10% each time, until you got where you wanted to be,
> that would be stair interpolation. If you used S spline the same way,
> that would also be stair interpolation.
>
> Several web sites report that FM SI Pro is bicubic stair interpolation
> at 12% per iteration, and several note that the results with "bicubic
> smoother" in CS2 is just as good. This sort of exchange is typical:

It seems to me that any linear filter applied multiple times is just another
different linear filter, and can be precomputed as such in advance, and
applied in the same amount of time it takes to do any other single filter.
Doing it iteratively seems like the dumb way to do it (if you're writing the
software, that is), and might also build up noise due to accumulated
roundoff errors, especially if computation is done in 8-bit mode.

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Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@...