Subject: Re: [linux-audio-dev] ladspa xml gui
From: David Olofson (david_AT_gardena.net)
Date: Sun Dec 10 2000 - 02:15:40 EET
On Friday 08 December 2000 07:17, Paul Barton-Davis wrote:
> [ dithering 24bit pixmap images to <24 bits ]
>
> >Are you saying that there isn't support for dithering from 24 bit
> >when uploading pixmaps? (Even Windoze does that... Don't know
> > enough about X, GDK and GTK+ to tell exactly where it would be
> > done here.)
>
> oh, X can do it all right, but the result is generally crapola.
Worse than dithering should look? Lower depth modes do look worse
than 24 bit color modes, but 15/16 bit isn't that bad. 256 color
mode is terrible though, and requires some kind of manual processing
for most RGB format graphics. (That's why many desktop environments
and applications have 16 or 256 color and highcolor icon sets.)
> as
> far as i can tell, there's a fair amount of graphic design skill
> involved in designing visual elements with shading etc. that work
> well at different bit depths. whatever dithering techniques X
> provides by default will screw up naive attempts (such as my own
> knobs, etc) because the artist didn't pay any attention to the
> thought that they might lose every other or even 2 out of 3 bits
> when the image was rendered.
Basically, since there is no (sane) dithering algorithm that can
determine which colors are the most important, you have to create
special versions for 256 color and 16 color screens.
For 15+ bits, all you have to do is
1) avoid long scales between very similar colors - those will
usually result in clearly visible "steps" in 16 and 15 bit
modes. (Only 5 bits of resolution per channel...)
2) DON'T dither! If you dither to some higher bit depth, and
then try to dither down to a lower bit depth, you'll get
"interesting" interference patterns betweer the original
and new dither patterns.
//David
.- M A I A -------------------------------------------------.
| Multimedia Application Integration Architecture |
| A Free/Open Source Plugin API for Professional Multimedia |
`----------------------> http://www.linuxaudiodev.com/maia -'
.- David Olofson -------------------------------------------.
| Audio Hacker - Open Source Advocate - Singer - Songwriter |
`--------------------------------------> david_AT_linuxdj.com -'
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