RE: [GM-core] PixelPacket formats

> Are there any strong reasons to continue to support the ARGB layout?

I am not sure, but the strong argument for support a particular arrangement
for me was whether the native graphic card arrangement matched. The idea was
that there would some big advantages if the pixels you have inside the core
could map exactly to those of your graphic card hardware. You can them
actually use graphic card memory as part of a GM pixel buffer if you need
to. On the PC, I used this years ago to do some really cool SDL integration
were you could "watch" an image processing algorithm operation in real time.
I don't know if anyone is counting on this for the case you describe on the
Mac. I must assume that ARGB is the "native" pixel format in memory for Mac
graphics cards, but this could have changed or maybe was never correct.

Also - the idea is that even if you need to do quick double buffered memory
copies between a GM buffer of pixels and a graphics card buffer, you will be
able to get substantially better performance if the two formats are
identical. I don't think that this was every really verified by experiment.

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Bob
Friesenhahn
Sent: Sunday, September 26, 2004 10:03 AM
To: GraphicsMagick APIs; GraphicsMagick Core
Subject: [GM-core] PixelPacket formats

PixelPacket is the structure for storing TrueColor pixels and color 
palette entries in GraphicsMagick.  Currently there are three 
structure layouts supported:

Big endian processors:		RGBA
Macintosh (macintosh defined):	ARGB
Otherwise (mostly x86):		BGRA

I would like to eliminate support for the ARGB pixel layout 
(apparently used by MacOS) since it is not well supported by OpenGL 
and LCMS.  It is useful to be able to provide pixels in the native 
format to third-party software in order to avoid extra memory 
allocations and data copying.

Are there any strong reasons to continue to support the ARGB layout?

Bob
======================================
Bob Friesenhahn
[email protected]
http://www.simplesystems.org/users/bfriesen


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