1-bit tiff rendering

[Ed McNierney]

Pierre -

MapServer optimizes for fast image rendering, which means quick
subsampling of pixels from an image.  This is a very fast way to produce
the output map, but does not produce the best image.  Using gdaladdo or
a similar mechanism to create different source resolutions is a very
good idea, because it gives you the ability to produce higher-quality
intermediate resolutions.  They will still be subsampled if necessary,
but they will be closer to the "original" and look better.  In some
cases you can control the rendering scales so the only output
resolutions permitted are those that are identical to ones you have
overviews for.

        - Ed

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

-----Original Message-----
From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On
Behalf Of GIRAUD Pierre
Sent: Tuesday, September 14, 2004 11:56 AM
To: MAPSERVER-USERS at LISTS.UMN.EDU
Subject: [UMN_MAPSERVER-USERS] 1-bit tiff rendering

  Hi list,

I do have B&W tif's (1-bit coded), and when I want to get those rendered
by mapserver, I obtain bad restitution within some zoomscales. The map
image is also B&W. I would prefer it to be in greyscale.
Can I easily do this with mapserver.

To have this working, I transformed my tiff manually with photoshop to
have an 8-bit greyscale image. Can I do this easily with the libtiff
tools ?
And then I applied gdaladdo to get overviews. This last operation seems
to be necessary to have a good rendering.

Did some of you have similar problems and got it work ?

Pierre GIRAUD