Afternoon Simone / Michael:
Time for me to ask a question on the user list ... I was looking to produce a
black and white image to feed into the raster to vector process. And it was not
as easy as I remember.
I did find a few interesting parts to the puzzle:
- The JAI Operation binarize seems to do the trick
- OperationJAI can wrap up a JAI OperationDescriptor in geotools clothing so it
can be applied to grid coverages ... but got stuck as Binarize operation does
not seem to run around as an instance you can pass in to JAIOperation; and it
is not captured as a subclass either
Moving on there is a utility class:
- Operations - looks very useful but could not sort out how to get it to
threshold my raster
Finally I found:
- ImageWorker a very easy class for working on images directly ...
- ... but then you need to go through the steps to wrap the result back up in a
coverage using a CoverageFactoryFinder etc...
So the question is? Did I miss something - why was this one so hard :-)
For reference here is the sample code I ended up with:
GridCoverage2D gradient = (GridCoverage2D)
Operations.DEFAULT.gradientMagnitude( dem );
RenderedImage rawImage = gradient.getRenderedImage();
ImageWorker worker = new ImageWorker( rawImage );
worker.binarize(maxSlope);
RenderedImage processed = worker.getRenderedImage();
GridCoverageFactory fac = CoverageFactoryFinder.getGridCoverageFactory(null);
GridCoverage2D slope = fac.create( "slope", processed, dem.getEnvelope() );
Notes:
- I think last time I went straight to JAI operations and used the threshold
operation
- I noticed ImageWorker had a AreaOfInterest construct that could be turned
into a Java shape? Could we use that for a super fast raster to vector
calculation? or is it likely to be just as processor intensive as our own?
Jody
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