is it the same RGBA, though? (was Re: Graphic Images)

Subject: is it the same RGBA, though? (was Re: Graphic Images)
From: Paul Rohr (
Date: Fri Apr 20 2001 - 14:34:38 CDT

At 09:33 AM 4/20/01 +0200, Hubert Figuiere wrote:
>According to Dom Lachowicz <>:
>> In this case, everything could be done entirely XP. But now, we depend on
>> being able to basically extract RGB(A) buffers from images and paste them
>> onto drawables in *every* graphics impl, not just Unix. Until we go
>> XP here (which I doubt that we'll ever do), Graphics _must_ know about
>> Image's implementation, which is perfectly fine here because *Graphics'
>> is a creator/manager/renderer of a specific subclass of GR_Image.
>RGBA is not a problem at all for BeOS, for MacOS X, and for MacOS < X I
>think we will be able to deal with it if it is not supported (but I doubt
>it isn't).
>So receiving a raw pixmap in RGB(A) is really XP.

I'd like to drill down a bit on the "RGB(A) everywhere" hypothesis.

The last time I did any XP image-handling work was in the summer of 1995.
At that time, the platform-specific blitting APIs on Mac, Windows and X all
had subtle variations in the RGB buffer formats they expected. Stupid
stuff, like top-to-bottom vs. bottom-to-top, or changing the padding width
on each scanline.

Thus, at the time I could run the same XP decoder to emit individual pixels,
but I needed platform-specific routines to construct the necessary
uncompressed buffers to bit-blast to the screen. Running that kind of
process in reverse to get back to a PNG or JPEG sounds even more obnoxious.

Is this not a problem any more? It'd be wonderful to hear that things have
been standardized enough that you could hand the exact same uncompressed
RGB(A) buffer to drawing routines on most or all of our supported platforms.

I'm not holding my breath, though. ;-)


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