Raster Support

[Frank Warmerdam]

Denis Lalonde wrote:
> Now Questions:
> 
> 1 - Displayed with the above outputformat, the resulting image quality 
> is poor. I’m not sure what the correct terminology is, but it doesn’t 
> seem like it is using all the colors it should. If I change my Output 
> format to Jpeg, the resulting image appears great...although performance 
> seems affected. All other output formats result in "poor" image quality 
> too. What am I missing?

Denis,

The default color compression method for RGB raster rendering to 256
color output is simple "nearest" color selection in a fixed color cube.
You can turn on dithering to improve results.  Some discussion of
this can be found in the Raster Data Access HOWTO at:

http://mapserver.gis.umn.edu/docs/howto/raster_data/#bit-rgb-rendering


> 2 - While "panning" around my map, if I get to the "edge" of one of the 
> tiles displayed in the map, I get the following PHP error:"Warning: 
> [MapServer Error]: IReadBlock failed at X offset 9, Y offset 39: 
> GDALRasterIO() failed: drawGDAL()"

Is this with the MrSID file or the TIFF file?  This indicates a bug in
GDAL by the looks of it.  Or possibly a corrupt file.

> 3 - I've searched, but didn't find anything regarding MrSid in 
> PHPMapScript. It's not supported correct?

MrSID is supported if you are using a version of GDAL built with MrSID
support enabled.  It requires extra external libraries and is not enabled
by default.  If you are using prepackaged binaries it is likely not
available.

Newish MS4W's do include mrsid I think.

Best regards,

-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo, http://osgeo.org