Java Advanced Imaging GradientMagnitudeDescriptor

I have been reading the API and documentation (http://java.sun.com/products/java-media/jai/forDevelopers/jai1_0_1guide-unc/Analysis.doc.html 9.5 Edge Detection) and have come across the GradientMagnitudeDescriptor class. Thing is, the create() Method of this class returns a static RenderedOp (whatever that is).

How do I deal with this static RenderedOp in terms of extracting coordinates?

Sorry if this is a stupid question, but I am completely new to image pro开发者_开发问答cessing and analysis.

Take a look at Listing 9-4 Example GradientMagnitude Operation and see if that helps any. You don't call the create method on the GradientMagnitudeDescriptor class, instead you call the JAI.create() method with the "GradientMagnitude" operation name. JAI.create() returns an instance of RenderedOp which can be cast to PlanarImage if you want.