Hello Mickael
Michael Owonibi a écrit :
> I am wondering how do I derive/define a gridcoverage2d from an array of
> image cell values, arranged in a way such as this –{ pixel 1 band1,
> pixel 1 band 2, pixel 1 band 3 …..pixel 1 band m, pixel 2 band 1, pixel
> 2 band 2, pixel 2 band 3 …pixel 2 band m …….pixel n band m} (...snip...)
GridCoverage2D are wrappers around RenderedImage, adding metadata like bounding
box, etc. So the question is how to create a RenderedImage for data arranged in
the way you describe. So the first steps described below is about creating a
J2SE image from your data. Only the last steps are GeoTools-specific.
---- BEGIN STANDARD JAVA API -----------------------------------------------
1) Create a DataBuffer wrapping your data. Note that you don't need
to copy your data; they will be directly wrapped. You will need to
select one of the DataBuffer subclass matching your data type, for
example DataBufferFloat if they are float values.
http://java.sun.com/javase/6/docs/api/java/awt/image/DataBuffer.html
2) Create a SampleModel that describe the way your data are arranged.
In the above case, its look like that the following subclass would
fit:
http://java.sun.com/javase/6/docs/api/java/awt/image/PixelInterleavedSampleModel.html
3) Create a WritableRaster with the above SampleModel and DataBuffer
(no subclass to look at in this case):
http://java.sun.com/javase/6/docs/api/java/awt/image/WritableRaster.html
You could stop at this point since (if my memory serve me right) there is a
GridCoverageFactory method which accept directly a Raster. However if you want
more control it may be worth to continue.
Note: the following step could also be skipped if you create a JAI image (which
accepts null ColorModel), but for now I'm assuming you will create a J2SE image,
which require non-null ColorModel.
4) Create a ColorSpace which describe how you want to translate the values
to colors. Note that this is not styling; we are just defining the initial
representation of your data. Note that if you have 1, 3 or 4 bands, one of
the pre-defined ColorSpace could fit. But I assume that you have an
arbitrary number of bands in which case you may need to define your own
ColorSpace:
http://java.sun.com/javase/6/docs/api/java/awt/color/ColorSpace.html
5) Define a ColorModel compatible with the SampleModel you defined at step 2.
Its look like that ComponentColorModel would fit. It requires a ColorSpace,
which is why I wrote this step 4 just before.
http://java.sun.com/javase/6/docs/api/java/awt/image/ComponentColorModel.html
6) Create a BufferedImage, giving to the constructor the ColorModel and the
WritableRaster you created in the above steps.
http://java.sun.com/javase/6/docs/api/java/awt/image/BufferedImage.html
You can display you BufferedImage using a Swing widget for example in order to
test it.
---- END OF STANDARD JAVA API -----------------------------------------------
Once you have your BufferedImage defined at step 6 or you raster defined at step
3, you have to:
a) Create a SampleDimension for each band. Note that SampleDimensions just
describes the band (they are metadata) - they do not contain the data;
the later are stored in the DataBuffer you created at step 1 and can
have whatever layout you managed to describe through a SampleModel.
b) Use one of the GridCoverageFactory method for creating a GridCoverage2D
using the RenderedImage or Raster, together with you bounding box, CRS
and the array of SampleDimensions.
Martin
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