[PD] [pix_data] - convert rgb values to pd canvas format

[William Huston]

Well if there are 4x 8 bit values (RGB+alpha) =32 bits trying to be
encoded/decoded into a single precision float, there will be loss of
fidelity.

It amazes me that it works for encoding 24 bit values (I tested it for RGB
only and can send a demo patch, or check the one Katja posted here:
http://lists.puredata.info/pipermail/pd-list/2015-12/112694.html )

Check out Katja's page and video about "Pd Double" for the best explanation
of this problem.

I personally wish there was a 32 bit integer data type in Pd for counters
and binary registers and such, which I know will never get converted into
floats, and risk strange rounding errors or noise in the Least Significant
Bits.


On Thursday, December 31, 2015, João Pais <jmmmpais at gmail.com> wrote:
> Ok. Do you know what should be done to convert to Pd's rgb format?
>
>> I'm pretty sure the 4th value is alpha
>>
>> Sent from my iPhone
>>
>>> On Dec 31, 2015, at 7:53 AM, João Pais <jmmmpais at gmail.com> wrote:
>>>
>>> Hello list,
>>>
>>> I'm trying to use [pix_data] to get the RGB values from an image, and
color a canvas using them. But the results come out a bit weird, as not all
colors match.
>>>
>>> I can try to some a more detailed patch in a couple of days, but wanted
to ask first the there is any example of how to use the values coming out
of [pix_data]:
>>> - should the gray value be used?
>>> - the middle outlet should send a list of RGB values, but I noticed
that instead a list of 4 values comes out. This isn't documented, what is
the 4th value?
>>>
>>> Attached are 2 pictures that should exemplifiy the issue:
>>> - rgb.tif - a rgb palette
>>> - rgb-conv.tif - the result after my interpretation of the data
>>>
>>> Best,
>>>
>>> Joao
>>> <rgb.tif>
>>> <rgb-conv.tif>
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