[mapserver-users] Rasters

[Brent Fraser]

Frank,

   Does MapServer now use GDAL by default to read tiffs (instead of its 
own tiff handling), or do you need to specify a CONNECTIONTYPE?  Or 
perhaps create a VRT file referencing the tiff to force the use of GDAL 
to read the tiff?

Best Regards,
Brent Fraser


On 6/16/2011 8:12 AM, Frank Warmerdam wrote:
> On 11-06-16 06:37 AM, afarrell wrote:
>> Hi,
>>
>> I've converted some 8 bit rasters to GeoTIFF format and spherical 
>> mercator
>> projection using FME.
>> I'm getting large blue edges where the tiles meet:
>>
>> http://dl.dropbox.com/u/23077047/Misc1use/rasters.jpg
>> http://dl.dropbox.com/u/23077047/Misc1use/rasters.jpg
>>
>> In ArcGIS the tiles appear seamless.
>>
>> Is this because MapServer do not support the nodata tiff tag, as it 
>> is not
>> officially part of the geotiff standard
>> (http://www.awaresystems.be/imaging/tiff/tifftags/gdal_nodata.html). I
>> do not believe there is a problem with the files we are writing, as 
>> other
>> applications (e.g. ArcCatalog) pick up on the nodata value just fine.
>
> Annette,
>
> I would be interested in seeing a gdalinfo report on one of the
> GeoTIFF files produced with FME.  The problem isn't that the
> tag is non-standard (after all it is a GDAL produced tag and
> MapServer uses GDAL as does FME and ArcGIS).  The problem is
> just in the MapServer raster layer implementation and whether it
> honours the metadata.
>
> An immediate work around is to figure out what that blue pixel
> value is and set the OFFSITE keyword in your raster layer to
> match it.
>
> For instance if the blue were red=0, green=149, blue=189 you
> would add the following in the LAYER:
>
>   OFFSITE 0 149 189
>
> Ideally though, MapServer would pick it up automatically.
>
>> Another potential solution is to add an alpha band to the raster 
>> instead of
>> a nodata value. Do you think MapServer will support this?
>
> yes
>
>> Would using ecw images resolve the issue?
>
> no, and it is often very difficult to keep track of nodata
> areas in lossily compressed formats like ecw, mrsid, jpeg2000
> and jpeg.
>
>
>