[Mapserver-users] tiffs and 256 colors

[Ed McNierney]

Dylan -

Are you using transparency to blend the two images?  I assume so, otherwise you wouldn't need to display them both at once.

If you have a 64-color grayscale layer and want to display a 12-color image blended with it, the resulting image will require 64 * 12 = 768 colors, not counting duplicates.

However, it can be done....

http://test.topozone.com/map.asp?z=10&n=5189336&e=594639&s=200&size=m&layer=DRGSR

	- Ed

Ed McNierney
President and Chief Mapmaker
TopoZone.com / Maps a la carte, Inc.
73 Princeton Street, Suite 305
North Chelmsford, MA  01863
ed@topozone.com
(978) 251-4242 

-----Original Message-----
From: Dylan Keon [mailto:keon@nacse.org]
Sent: Wednesday, March 05, 2003 5:38 PM
To: mapserver-users
Subject: [Mapserver-users] tiffs and 256 colors


I'm trying to display a colored tiff (single DRG 1:24K quad) on top of a 
grayscale shaded relief tiff.  When using 8-bit PNG output, the DRG 
appears as grayscale if both layers are displayed at the same time.  If 
I turn off the shaded relief layer, the DRG is colored correctly.

I've reduced the color depth of the grayscale shaded relief image to 64 
colors using Imagemagick, but still have the same problem.  Shouldn't 
that make enough colors available between the shaded relief (64 colors) 
and the DRG (12 colors)?

I've experimented with both 3.6.4 and today's 3.7 CVS version.  I'm 
doing this through a PHP MapScript application, but I get the same 
result with each version's shp2img.  It does work ok if I use 24-bit 
output in 3.7, but I'd like to stick with 8-bit if I can.

Thanks for any tips.

--Dylan

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