Hi Filipe,
so your data is byte at the end.
note that when applying MEAN (+/-)n* STDDEV you should not exceed the input
range (0, 255 on bytes).
You can try using n=1 or just set 0 instead of negative value.
In reference to the histogram percentile computations, you may need to do
some math or compute them with QGIS.
You may want to look at this piece of code to better understand how
percentiles can be computed.
https://github.com/qgis/QGIS/blob/master/src/core/raster/qgsrasterinterface.cpp#L533-L560
Long story short, you have to run gdalinfo -hist and take note of number of
buckets as well as "from" and "to" range.
Then start summing bucket count until you get the desired percentage (as an
instance you will get a 2% once the cumulative sum is 2% with respect to
the total number of pixels composing your image, usually Width*Height).
The number of bucket used to reach the 2% allows you to compute the related
MIN value. (something like: "from" + numBuckets * (range/totalNumBuckets)).
The same for the 98% to compute the MAX.
You may want to check some histogram and percentiles topic around on
internet to better understand this concepts.
Hope this helps.
Cheers,
Daniele
On Tue, Aug 1, 2017 at 5:14 PM, Filipe <[email protected]> wrote:
> Hello
> Thank you for your reply.
>
> I did what you sugested, and we're getting somewhere!
>
>
> using the formulas you sugested:
>
> <RasterSymbolizer>
> <ChannelSelection>
> <RedChannel>
> <SourceChannelName>1</SourceChannelName>
> <ContrastEnhancement>
> <Normalize>
> <VendorOption
> name="algorithm">StretchToMinimumMaximum</VendorOption>
> <VendorOption name="minValue">-55.2689</VendorOption>
> <VendorOption name="maxValue">214.7722</VendorOption>
> </Normalize>
> </ContrastEnhancement>
> </RedChannel>
> <GreenChannel>
> <SourceChannelName>2</SourceChannelName>
> <ContrastEnhancement>
> <Normalize>
> <VendorOption
> name="algorithm">StretchToMinimumMaximum</VendorOption>
> <VendorOption name="minValue">-41.9121</VendorOption>
> <VendorOption name="maxValue">163.9293</VendorOption>
> </Normalize>
> </ContrastEnhancement>
> </GreenChannel>
> <BlueChannel>
> <SourceChannelName>3</SourceChannelName>
> <ContrastEnhancement>
> <Normalize>
> <VendorOption
> name="algorithm">StretchToMinimumMaximum</VendorOption>
> <VendorOption name="minValue">-22.1867</VendorOption>
> <VendorOption name="maxValue">77.2479</VendorOption>
> </Normalize>
> </ContrastEnhancement>
> </BlueChannel>
> </ChannelSelection>
> </RasterSymbolizer>
>
> my raster info is
>
> C:\DATA\raster>gdalinfo myRaster.tif
> Driver: GTiff/GeoTIFF
> Files: myRaster.tif
> myRaster.tif.ovr
> myRaster.tif.aux.xml
> Size is 23861, 16880
> Coordinate System is:
> PROJCS["WGS 84 / UTM zone 29N",
> GEOGCS["WGS 84",
> DATUM["WGS_1984",
> SPHEROID["WGS 84",6378137,298.257223563,
> AUTHORITY["EPSG","7030"]],
> AUTHORITY["EPSG","6326"]],
> PRIMEM["Greenwich",0,
> AUTHORITY["EPSG","8901"]],
> UNIT["degree",0.0174532925199433,
> AUTHORITY["EPSG","9122"]],
> AUTHORITY["EPSG","4326"]],
> PROJECTION["Transverse_Mercator"],
> PARAMETER["latitude_of_origin",0],
> PARAMETER["central_meridian",-9],
> PARAMETER["scale_factor",0.9996],
> PARAMETER["false_easting",500000],
> PARAMETER["false_northing",0],
> UNIT["metre",1,
> AUTHORITY["EPSG","9001"]],
> AXIS["Easting",EAST],
> AXIS["Northing",NORTH],
> AUTHORITY["EPSG","32629"]]
> Origin = (625033.424520000000484,4248219.836620000191033)
> Pixel Size = (0.103860000000000,-0.103860000000000)
> Metadata:
> AREA_OR_POINT=Area
> TIFFTAG_SOFTWARE=pix4dmapper
> Image Structure Metadata:
> COMPRESSION=LZW
> INTERLEAVE=PIXEL
> Corner Coordinates:
> Upper Left ( 625033.425, 4248219.837) ( 7d34' 7.07"W, 38d22'24.38"N)
> Lower Left ( 625033.425, 4246466.680) ( 7d34' 8.19"W, 38d21'27.52"N)
> Upper Right ( 627511.628, 4248219.837) ( 7d32'24.97"W, 38d22'23.12"N)
> Lower Right ( 627511.628, 4246466.680) ( 7d32'26.11"W, 38d21'26.26"N)
> Center ( 626272.526, 4247343.258) ( 7d33'16.59"W, 38d21'55.32"N)
> Band 1 Block=23861x1 Type=Byte, ColorInterp=Red
> Min=0.000 Max=255.000
> Minimum=0.000, Maximum=255.000, Mean=79.752, StdDev=67.510
> NoData Value=-10000
> Overviews: 11931x8440, 5966x4220, 2983x2110, 1492x1055, 746x528, 373x264,
> 187x132
> Metadata:
>
> STATISTICS_COVARIANCES=4557.639431244172,3461.157875865516,1616.247181916951,8018.146929498016
> STATISTICS_MAXIMUM=255
> STATISTICS_MEAN=79.751677803277
> STATISTICS_MINIMUM=0
> STATISTICS_SKIPFACTORX=1
> STATISTICS_SKIPFACTORY=1
> STATISTICS_STDDEV=67.510291214959
> Band 2 Block=23861x1 Type=Byte, ColorInterp=Green
> Min=0.000 Max=255.000
> Minimum=0.000, Maximum=255.000, Mean=61.009, StdDev=51.460
> NoData Value=-10000
> Overviews: 11931x8440, 5966x4220, 2983x2110, 1492x1055, 746x528, 373x264,
> 187x132
> Metadata:
>
> STATISTICS_COVARIANCES=3461.157875865516,2648.170496677781,1243.180669732085,6133.734519685802
> STATISTICS_MAXIMUM=255
> STATISTICS_MEAN=61.008562632494
> STATISTICS_MINIMUM=0
> STATISTICS_SKIPFACTORX=1
> STATISTICS_SKIPFACTORY=1
> STATISTICS_STDDEV=51.460377929799
> Band 3 Block=23861x1 Type=Byte, ColorInterp=Blue
> Min=0.000 Max=226.000
> Minimum=0.000, Maximum=226.000, Mean=27.531, StdDev=24.859
> NoData Value=-10000
> Overviews: 11931x8440, 5966x4220, 2983x2110, 1492x1055, 746x528, 373x264,
> 187x132
> Metadata:
>
> STATISTICS_COVARIANCES=1616.247181916951,1243.180669732085,617.954007884253,2767.896495658875
> STATISTICS_MAXIMUM=226
> STATISTICS_MEAN=27.530599208965
> STATISTICS_MINIMUM=0
> STATISTICS_SKIPFACTORX=1
> STATISTICS_SKIPFACTORY=1
> STATISTICS_STDDEV=24.858680734992
> Band 4 Block=23861x1 Type=Byte, ColorInterp=Alpha
> Min=0.000 Max=255.000
> Minimum=0.000, Maximum=255.000, Mean=154.461, StdDev=124.617
> NoData Value=-10000
> Overviews: 11931x8440, 5966x4220, 2983x2110, 1492x1055, 746x528, 373x264,
> 187x132
> Metadata:
>
> STATISTICS_COVARIANCES=8018.146929498016,6133.734519685802,2767.896495658875,15529.34978118977
> STATISTICS_MAXIMUM=255
> STATISTICS_MEAN=154.46108783722
> STATISTICS_MINIMUM=0
> STATISTICS_SKIPFACTORX=1
> STATISTICS_SKIPFACTORY=1
> STATISTICS_STDDEV=124.61681179195
>
> Now what can i do to come closer to the original one? (to get that
> "blueish" on the water)
> You mentioned "computing percentiles based on histograms". how can i do
> that?
> Regards
> ------------------------------
> View this message in context: Re: Raster Normalize
> <http://osgeo-org.1560.x6.nabble.com/Raster-Normalize-tp5330021p5330071.html>
>
> Sent from the GeoServer - User mailing list archive
> <http://osgeo-org.1560.x6.nabble.com/GeoServer-User-f3786390.html> at
> Nabble.com.
>
> ------------------------------------------------------------
> ------------------
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> Please make sure you read the following two resources before posting to
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--
Regards,
Daniele Romagnoli
==
GeoServer Professional Services from the experts! Visit http://goo.gl/it488V
for more information.
==
Ing. Daniele Romagnoli
Senior Software Engineer
GeoSolutions S.A.S.
Via di Montramito 3/A
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Italy
phone: +39 0584 962313
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