Path: utzoo!attcan!uunet!wuarchive!mit-eddie!uw-beaver!cornell!johnhlee
From: johnhlee@bass.cs.cornell.edu (John H. Lee)
Newsgroups: comp.sys.amiga
Subject: Re: 24/32 Bit Color
Message-ID: <47264@cornell.UUCP>
Date: 18 Oct 90 16:41:53 GMT
References: <3568@mindlink.UUCP>
Sender: nobody@cornell.UUCP
Reply-To: johnhlee@cs.cornell.edu (John H. Lee)
Organization: Cornell Univ. CS Dept, Ithaca NY
Lines: 31
Summary:
Followup-To:

In article <3568@mindlink.UUCP> a45@mindlink.UUCP (Ken Cooper) writes:
>A "24 bit" adapter allocates 8 bits per color (256 levels) for a total possible
>number of colors of 16,777,216. A "32 bit" adapter allocates the same number of
>levels per color, but adds an extra 8 bits (256 levels) of ALPHA CHANNEL. Alpha
>channel can be thought of as storage for a soft-edged MASK, which can be used
>to define what part of the image is or is not background. By allocating 256
>levels for the mask or alpha channel, the mask can have 256 levels of
>transparency. This is important when attempting to smoothly compose images and
>for creating high quality effects.

Okay people, time for a little review.  Yes, I meant it when I said that
32 bits are allocated for 32 bits of COLOR information, 11 bits for green,
11 bits for red, and 10 bits for blue (the human eye is less sensitive for
blue, so blue usually gets the short end of the byte.)

Alpha channels, depth, etc. do require additional bits, but they are not
counted when counting Bits for Color.  They are modifiers that affect how
the pixels are displayed in the final result and pixel priority, etc.,
but not the actual pixel color stored in a frame buffer.

If you want to include these extra modifiers, then I believe several IRIS
models have 48+ bits per pixel, but only 24 bits of color.

Of course, manufacturers may say 32 bits per pixel but have only 24 bits of
RGB.  They mean 32 bits of Pixel Information.  Not the same, but then these
are marketing specs, no?

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The DiskDoctor threatens the crew!  Next time on AmigaDos: The Next Generation.
	John Lee		Internet: johnhlee@cs.cornell.edu
The above opinions of those of the user, and not of this machine.