>Stop dreaming about color selection on the WWW.
>Netscape doesn't neccessarily use a "standard 256-colour palette".
>E.g. my Netscape uses a 2-colour palette. Others use a max. of 64 or
>227 colours.
For the purposes of this message, let us refer to the standard palette
in Paint Shop Pro, the evenly distributed 6x6x6 color palette, or the
"browser-safe" palette as the BSP.
I'm not sure where you get 64 and 227, but it is true that Netscape
does not always use the same palette. I think we can discount your
2-colour palette. No amount of selecting any significant number of
colors is going to make a colourful image appear any better in your
situation. Everyone else fits in one of the following categories, from
the information I have been able to glean:
Windows 16 color -- does not use the BSP but does not dither colors
either, so this situation need not be considered for dithering.
Windows 256 color (8 bit) -- this is the platform the BSP is most
useful for.
Mac 8 bit -- Netscape uses the BSP supplemented with additional
colors.
X-Windows -- Usually uses a 125 color 5x5x5 color palette, dithering
images saved with the BSP pretty badly. Sometimes a different palette
is used with the same results.
Windows 15 or 16 bit -- colors are not dithered.
Mac 15 or 16 bit -- I haver received one report of images saved with
the BSP dithering. I believe this is not the most common situation,
however, or I probably would have heard of other reports of the same
problem.
All systems at True Color -- There is no dithering.
These are the setups I am familiar with. Any others are rarefied
enough not to matter significantly.
Of all these scenarios, only X Windows at 8 bit and Macs at 15 or 16
bit show dithering of images saved with the BSP. All the rest show
images that display either as well or better than the unadjusted
image. If you don't specifically apply the 5x5x5 color cube to the
image, X Windows will probably dither equally poorly before and after
applying the BSP, so we can discount it as well. A similar argument
can be made for Macs at 15 or 16 bit.
OK. That takes care of Netscape. What about the other browsers? Well,
Internet Explorer uses the BSP at 8 bit. So do many other browsers.
Those that do not tend to allocate colors as they are encountered. If
the BSP is used, all images will appear clearly.
The bottom line is that applying the BSP vastly improves the display
for Windows and Macs at 8 bit without adversely affecting the display
on other platforms. Therefore, using the BSP has tremendous use.
All that being said, it is not appropriate for use with photographic
images and other images containing continuous gradations of color.
These are better represented in the JPEG format.
For further information on this subject with example images, go to
http://the-light.com/netcol.html
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Victor Engel Vector Angle
http://the-light.com http://www.onr.com/user/lights