[mapserver-users] processing scale=auto with float multibands rasters

Tue Aug 4 10:50:18 PDT 2015

Hi,

I suppose that Even means that with AUTO setting Mapserver is analyzing the min/max pixel values from inside the BBOX of each GetMap and then scales pixel values to 0-256 for the output.  One totally black or white pixel within the BBOX can make the result from 64bit source very bad.

I would try to use LUT instead of SCALE http://www.mapserver.org/input/raster.html#special-processing-directives.

-Jukka Rahkonen-

-----Alkuperäinen viesti-----l
Lähettäjä: mapserver-users-bounces at lists.osgeo.org [mailto:mapserver-users-bounces at lists.osgeo.org] Puolesta Andrea Peri
Lähetetty: 4. elokuuta 2015 20:07
Vastaanottaja: Even Rouault
Kopio: mapserver-users at lists.osgeo.org
Aihe: Re: [mapserver-users] processing scale=auto with float multibands rasters

Hi Even,

thx for response.

Please can you help me to better understand the question ?

My raster is effectively a 18000 x 24000 px image with tiles.

it have a tile size of 1024 x 1024 produced from gdalwarp:

gdalwarp -s_srs EPSG:32632 -t_srs EPSG:32632 -overwrite --config GDAL_CACHEMAX 1000 -wm 1000 -co TILED=YES -co COMPRESS=NONE -co
BLOCKXSIZE=1024 -co BLOCKYSIZE=1024 -co BIGTIFF=YES -co SPARSE_OK=TRUE .......

and also have overviews from

gdaladdo --config GDAL_CACHEMAX 1500 -ro -r average ..... 2 4 8 16 32
64 128 256 512 1024

If I understand correctly your info.
The mapserver could search the min/max using only the first tile ?

This mean that it more probably found always only 0 values or near 0 values beacuse these could be the values in the first tile.

And so it return a white image because the min/max is always min=0/
max=0 (or something quite like this)
I understand correct ?

thx,

A.

2015-08-04 16:01 GMT+02:00 Even Rouault <even.rouault at spatialys.com>:
> On Monday 03 August 2015 11:02:43 Andrea Peri wrote:
>> Hi,
>> I have a geotiff multibands with float64 values to serve with a wms 
>> mapserver service.
>>
>> With this kind of rasters,
>> is affordable the directive
>>
>>     PROCESSING "BANDS=4,3,2"
>>     PROCESSING "SCALE=AUTO"
>>
>> (the 4,3,2 are the red,green,blue channels)
>>
>> Infact it seem do nothing.
>>
>> Instead all work well if I set:
>>
>>     PROCESSING "BANDS=4,3,2"
>>     PROCESSING "SCALE_1=0.01,0.2"
>>     PROCESSING "SCALE_2=0.01,0.2"
>>     PROCESSING "SCALE_3=0.01,0.2"
>>
>> where ii use the min=0.01 and max=0.2 But I like to have the exact 
>> values of min/max for every raster.
>
> Andrea,
>
> SCALE=AUTO should work but looking at the actual implementation I can 
> see it computes the min/max on the pixel values intersecting the 
> requested area, and not on the whole raster as I'd have expected. So 
> in a tiling context, it will likely not produce the expected result.
>
> Even
>
> --
> Spatialys - Geospatial professional services http://www.spatialys.com

--
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Andrea Peri
. . . . . . . . .
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