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Re: Image rescaling

From: David Kastrup
Subject: Re: Image rescaling
Date: Mon, 15 Sep 2014 17:13:53 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/24.4.50 (gnu/linux)

Stefan Monnier <address@hidden> writes:

>> Rescaling is apparently a pretty tricky thing that is mostly implemented
>> wrong:
>> http://www.4p8.com/eric.brasseur/gamma.html
> Rescaling an image is exactly the same problem as resampling an audio
> file (e.g. to play it at 48KHz instead of the 44.1KHz used on the CD
> from which it came).
> Doing it naively works, but in some cases gives very poor
> results, indeed.

Nice meditation but not related to the referenced article.  The article
is concerned about non-linear quantization.  That's "exactly the same
problem" as using a good 48kHz to 44.1kHz resampling algorithm on
uLaw-quantized audio data rather than linearly-quantized data.

Entirely different problem to mess up on.

David Kastrup

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