Re: [boost] GIL Review

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