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
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-------------------------------------------------------
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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