From: Matt Gruenke (mgruenke_at_[hidden])
Date: 2006-11-02 01:28:59
Fernando Cacciola wrote:
>Now, off the pixel/color topic.
>rom the Quicktime format disccusion: is it possible to supersample (rather
>than subsample) an image? That is, to take two or more consequtive pixels in
>a row and pretend is just one pixel?
>
You're talking about a subsampling (or decimating) iterator, instead of
an interpolating iterator? I believe the code structures necessary for
both of these tasks are largely identical - once you've worked out how
to do one, the other should be quite straight forward.
However, for most purposes where this is desirable, it is probably more
efficient to write a routine that resamples entire rows and columns at a
time. On the other hand, if you care more about conserving memory than
performance, interpolating iterators may be a good solution for image
scaling/zooming, and are not limited to images with non-uniform sample
structures.
> I ask because the lack of uniformity in
>even/odd pixels in the v210 format could be elegantly solved this way (that
>is if IIUC the problem).
>
>
You'd be discarding information, though. The reason chroma has half the
sampling frequency, in this case, is because it has been band-limited to
half the bandwidth of luma (a perceptual optimization). If you decimate
luma, you're going to loose information (given no assumptions about the
input data). So, it's fails as a simplification, because it's not
equivalent.
Matt