MESSAGE
DATE | 2016-12-13 |
FROM | Ruben Safir
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SUBJECT | Subject: [Learn] Bit Depth
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From learn-bounces-at-nylxs.com Tue Dec 13 19:50:22 2016 Return-Path: X-Original-To: archive-at-mrbrklyn.com Delivered-To: archive-at-mrbrklyn.com Received: from www.mrbrklyn.com (www.mrbrklyn.com [96.57.23.82]) by mrbrklyn.com (Postfix) with ESMTP id CD885161313; Tue, 13 Dec 2016 19:50:21 -0500 (EST) X-Original-To: learn-at-nylxs.com Delivered-To: learn-at-nylxs.com Received: by mrbrklyn.com (Postfix, from userid 1000) id A2D25161311; Tue, 13 Dec 2016 19:50:18 -0500 (EST) Date: Tue, 13 Dec 2016 19:50:18 -0500 From: Ruben Safir To: png-mng-implement-at-lists.sourceforge.net Message-ID: <20161214005018.GA10351-at-www.mrbrklyn.com> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) Cc: learn-at-nylxs.com Subject: [Learn] Bit Depth X-BeenThere: learn-at-nylxs.com X-Mailman-Version: 2.1.17 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: learn-bounces-at-nylxs.com Sender: "Learn"
Hello
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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