|FROM ||Ruben Safir
|SUBJECT ||Subject: [Learn] Bit Depth
|From learn-bounces-at-nylxs.com Tue Dec 13 19:50:22 2016
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Date: Tue, 13 Dec 2016 19:50:18 -0500
From: Ruben Safir
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Subject: [Learn] Bit Depth
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I am completely confused and befuddled by the IHDR entry for bit depth.
I was considering that I would lay out the images memory and fill it
in with a number of threads. That required that I know the number of
bits per pixel. I see that there are methods to convert 2d image
information into 3d information using matrix math, but I'm not really
concerned about that.
I have an image which in the gimp and every other program I have
described the image as sRBG format with an alpha channel. Sample
precision can be defined as 1,2,4,8, or 16 Bit Depth (sample precision).
The rule is that for PNG the sample depth can be only 8 or 16 with an
alpah channel for RBG color.
Indeed, I have 8 bit precision and color type of 6, and I've confirmed
this visually with od.
How can that be? I don't even know what that prepresents. The image
has almost 29,000 unique colors. That is not 2^8.
I've research then for nearly 2 days and can't find an explanation for
this and how it implimented. And I'm very stuck. Does this mean the
color is 2^8 x 2^8 x 2^8? That would be the 24 bit color I've come to
know and love.
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