Hi Luigi,
you can use the "ZonalStats" operation. It is an OperationJAI subclass
which uses the JaiTools ZonalStatistics operation.
With this class you can calculate the Minimum and Maximum of the image and
setting the right nodata value.
This class is located in the GeoTools module "gt-coverage" together with
other operations (see the link:
https://github.com/geotools/geotools/tree/master/modules/library/coverage/src/main/java/org/geotools/coverage/processing/operation).
The JaiTools ZonalStats documentation can be found here:
http://jaitools.org/docs/jaitools/stable/apidocs/
Hope this will help.
Cheers,
Nicola
2014-02-07 Daniele Romagnoli <[email protected]>:
> Hi Luigi,
> yesterday I was writing you this reply but there was a blackout in the
> whole building so... I have seen other guys already suggested something.
> Sending anyway my email for further info, just in case....
>
> ---------------------------------------------------------------------------------
> The GT Extrema operation is based on JAI Extrema op which doesn't support
> NoData so it doesn't know that -9999 is a noData and therefore it returns
> that value as the minimum.
> A workaround you may try is providing a ROI (Region Of Interest) based on
> a threshold value to exclude some regions of the input image from the
> computations.
>
> http://download.java.net/media/jai/javadoc/1.1.3/jai-apidocs/javax/media/jai/operator/ExtremaDescriptor.html
>
> You can create a ROI on top of the input RenderedImage using a threshold
> value. Only pixels inside the ROI will be taken into account by statistics.
>
> http://docs.oracle.com/cd/E17802_01/products/products/java-media/jai/forDevelopers/jai-apidocs/javax/media/jai/ROI.html#ROI%28java.awt.image.RenderedImage,%20int%29
>
> As an instance, if -9999 is the minimum "bad" value and you know that all
> your values are >= A (Where A > -9999), you can do
>
> ROI roi = new ROI(inputRenderedImage, A);
> OperationJAI op=new OperationJAI("Extrema");
> ParameterValueGroup params = op.getParameters();
> params.parameter("roi").setValue(roi);
> ....
>
> I know, that isn't the optimal solution (especially for the ROI
> computation) but it may help.
> Cheers,
> Daniele
>
>
>
> ==
> Our support, Your Success! Visit http://opensdi.geo-solutions.it for more
> information.
> ==
> Ing. Daniele Romagnoli
> Senior Software Engineer
>
>
> GeoSolutions S.A.S.
> Via Poggio alle Viti 1187
> 55054 Massarosa (LU)
> Italy
> phone: +39 0584 962313
> fax: +39 0584 1660272
>
> http://www.geo-solutions.it
> http://twitter.com/geosolutions_it
>
> -------------------------------------------------------
>
>
> On Thu, Feb 6, 2014 at 4:29 PM, Luigi Marotta <[email protected]>
> wrote:
> >
> > Hi list,
> > I'm trying to built a WPS to evaluate the basic statistic
> information of coverage data usign
> org.geotools.coverage.processing.OperationJAI.Extrema but minimum value is
> coincident with noData value (i.e. -9999, correctly reported as nodata by
> gdalinfo). Is there some method, in this class, to obtain the right
> minimum and maximum?
> > Thx
> >
> >
> >
> > Luigi Marotta
> > IT Specialist - Ariespace s.r.l - Spin off Company
> > Università degli Studi di Napoli "Federico II"
> > Centro Direzionale IS. A3
> > 80143 - Napoli - Italy
> > tel.: (+39) 08119564282
> > fax: (+39) 08119564223
> > mob.: (+39) 3478836273
> > skypecontact: live:luigi.marotta
> >
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> >
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--
==
Our support, Your Success! Visit http://opensdi.geo-solutions.it for more
information.
==
Ing. Nicola Lagormarsini
Junior Software Engineer
GeoSolutions S.A.S.
Via Poggio alle Viti 1187
55054 Massarosa (LU)
Italy
phone: +39 0584 962313
fax: +39 0584 1660272
http://www.geo-solutions.it
http://twitter.com/geosolutions_it
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