[mapserver-users] ECW Image Quality
steve.lime at dnr.state.mn.us
Tue Jan 22 09:16:18 EST 2002
Yup, MapServer does have an 8-bit output limitation. This is a function
of limitations within GD. A new version of GD has be available for
almost a year but is still in beta. I want to wait for the new GD API
and code to stabilize before heading into that mess. Hopefully soon.
Data & Applications Manager
500 Lafayette Road
St. Paul, MN 55155
>>> "brad" <brad at mapsolutions.com.au> 01/22/02 00:18 AM >>>
I noticed this as well. The reason for the poor quality is that GDAL
only return an 8 bit image for ECW. I get this from the following
"The current implementation reads any number of bands but returns only
eight bit image data" at the following URL.
Does MapServer itself have a limit to 8 bits for images other than ECW.
have only tried ECW as this is the image format most commonly used by
I also experienced the black image as I was zooming in close to the
I can't explain that, anyone else getting this ? I am also getting an
The specified CGI application misbehaved by not returning a complete set
HTTP headers. The headers it did return are:
abnormal program termination
when I try using an ECW image that is large (671 MB). It only happens
sometimes and if I look at the memory consumption on my machine it only
seems to happen when it gets to ~35MB usage for the mapserv.exe process.
the memory consumed is less than this approximate value then there is
problem displaying the image (albeit in 8 bit).
Hope this helps some.
GIS Application Specialist
Digital Mapping Solutions
Level 2, 2 Hardy Street
South Perth 6151
Ph: 08 9474 6311 Fax: 08 9474 6411
email: brad at mapsolutions.com.au
From: owner-mapserver-users at lists.gis.umn.edu
[mailto:owner-mapserver-users at lists.gis.umn.edu]On Behalf Of Richard
Sent: Tuesday, 22 January 2002 11:24 AM
To: mapserver-users at lists.gis.umn.edu
Subject: [mapserver-users] ECW Image Quality
I am displaying ecw color images in mapserver, but the color quality is
very poor. It looks like a palette
problem. The images look great in mapserver when displayed as a tiff,
the ecw images look great in the ecw viewer, but the ecw image displayed
via GDAL & mapserver look like paint-by-numbers.
Also, when I zoom in below I screen pixel == 1 image pixel, the ecw
goes to black.
Does anybody have any ideas?
Richard W. Greenwood, PLS
Greenwood Mapping, Inc.
Rich at GreenwoodMap.com
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