[PD] [pix_data] - convert rgb values to pd canvas format
Olivier Baudu
01ivier at labomedia.net
Mon Jan 11 22:54:53 CET 2016
Hi...
I've red this thread too late, sorry...
I've done the same thing a while ago and I've lost a of of time to
convert RGB output from [pix_data] for them to work with canevas...
For the archive, I join my solution...
But, it works with pd-extended, not vanilla+GEM only...
Here is the original post :
http://lists.puredata.info/pipermail/pd-list/2013-06/103145.html
Sorry "to arrive after the battle"...
°1ivier
Le 08/01/2016 22:58, João Pais a écrit :
> Thanks for your help. Here is the resulting patch, pix2canvas. Sooner or
> later it will join the other abstractions in the jmmmp library.
>
> Best,
>
> Joao
>
> 2016-01-01 13:10 GMT+01:00 Roman Haefeli <reduzent at gmail.com
> <mailto:reduzent at gmail.com>>:
>
>
> On Thu, 2015-12-31 at 18:01 +0100, João Pais wrote:
> > If understandable, I send this patch so that it's possible to see what
> > I'm doing.
> >
> >
> > The idea is actually to convert a pix into a bunch of canvases, pixel
> > per pixel - so that a "picture" can be shown on vanilla. Follow the
> > instructions in the patch, and everything should be clear.
> > The conversion is done in [pd RGB]. There are 2 versions, but they
> > have the same output.
>
> There are quite a few different color encodings around in Pd world. For
> the iemguis, there is a difference in encoding between sending a 'color'
> message and defining a color as creation argument. What you've done
> works well for sending 'color' messages to canvas, but not as a creation
> argument. If you want to define a color as creation argument, you have
> to encode it differently, namely as 6bit-per-channel value. So, instead
> of multiplying by 255 and powers of 256, you need to multiply by 63 and
> powers of 64. See attached patch.
>
> I guess the reason is a limitation in how Pd displays (and saves)
> numbers. Although 32-bit float numbers can fully represent 24bit integer
> numbers, numbers are saved with less precision in pd files (and text
> files), since they are truncated to 6 digits. This limitation is
> worked-around by reducing the resolution to 6 bits per channel. The
> highest number (the one representing white) is -262144. It does not
> exceed 6 digits and can be stored at full precision.
>
> Roman
>
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