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

[Andrea Peri]

Hi Jukka, I could open a feature request for this, but before I need
to understand if the results with this strategy are affordable for us.

Infact I do some test with a domain min/max lesser than 2x and it
results unaccepatable for our users. The raster are too poor
contrasted as reported me from our users.
So I'm not sure that an AUTO with a STD stretch and a multiplicator 2x
could be instead an acceptable solution.

I should do more tests...

Thx.



2015-08-04 20:29 GMT+02:00 Rahkonen Jukka (MML)
<jukka.rahkonen at maanmittauslaitos.fi>:
> Hi Andrea,
>
> For viewing purposes it is rather common to do LUT stretch by standard deviation which is not so sensible as min-max stretch. Consider making a feature request for a new enhanced PROCESSING AUTO directive which would do the STD stretch, possibly with an optional multiplication. 2 x STD might be a good default value.
>
> -Jukka Rahkonen-
>
> Andrea Peri wrote:
>
>> HI Jukka,
>> unfortunatelly, I cannot use the LUT because the raster I use is update weekly and every week it could change the min/max values for every bands (it has 11 bands).
>
>> Hovewer if it work using the min/max from get map , probably it could be ok form me.
>> The question s that even when the getmap request the entire bbox the image reported seem to be empty without no error log.
>
>
>
> 2015-08-04 19:50 GMT+02:00 Rahkonen Jukka (MML)
> <jukka.rahkonen at maanmittauslaitos.fi>:
>> 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
>>
>>
>>
>> --
>> -----------------
>> Andrea Peri
>> . . . . . . . . .
>> qwerty àèìòù
>> -----------------
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>
>
>
> --
> -----------------
> Andrea Peri
> . . . . . . . . .
> qwerty àèìòù
> -----------------



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