Java Doc for OperationJAI.java in  » GIS » GeoTools-2.4.1 » org » geotools » coverage » processing » Java Source Code / Java DocumentationJava Source Code and Java Documentation

The entry point for applying an operation is the usual OperationJAI.doOperation doOperation method. The default implementation forward the call to other methods for different bits of tasks, resulting in the following chain of calls:

OperationJAI.doOperation doOperation :	the entry point.
OperationJAI.resampleToCommonGeometry resampleToCommonGeometry :	reprojects all sources to the same coordinate reference system.
OperationJAI.deriveGridCoverage deriveGridCoverage :	gets the destination properties.
OperationJAI.deriveSampleDimension deriveSampleDimension :	gets the destination sample dimensions.
OperationJAI.deriveCategory deriveCategory :	gets the destination categories.
OperationJAI.deriveRange deriveRange :	gets the expected range of values.
OperationJAI.deriveUnit deriveUnit :	gets the destination units.
OperationJAI.createRenderedImage createRenderedImage :	the actual call to JAI.createNS JAI.createNS .

1. Converts source grid coverages to their geophysics view using (true). This allow to performs all computation on geophysics values instead of encoded samples.

Note: it would be possible to use ImagingParameters.parameters directly in some occasions.

 (hints).
 (
 .getName(), parameters, hints)
 

• Gets the for the target images by invoking the OperationJAI.deriveSampleDimension deriveSampleDimension(...) method.
• Applied the JAI operation using OperationJAI.createRenderedImage .
• Wraps the result in a GridCoverage2D object.

 double min = ranges[0].getMinimum() + ranges[1].getMinimum();
 double max = ranges[0}.getMaximum() + ranges[1}.getMaximum();
 return new NumberRange(min, max);
 

• The bandLists array length is equals to the number of source coverages.
• The bandLists[i] array length is equals to the number of sample dimensions in the source coverage i.
• The sample dimension for a band at index band in the source at index source is bandLists[source][band] .

This method shall returns an array with a length equals to the number of bands in the target image. If the sample dimensions can't be determined, then this method is allowed to returns null .

The default implementation iterates among all bands and invokes the OperationJAI.deriveCategoryderiveCategory and OperationJAI.deriveUnit deriveUnit methods for each of them. Subclasses should override this method if they know a more accurate algorithm for determining sample dimensions.
Parameters:
  bandLists - The set of sample dimensions for each source GridCoverage2Ds.
Parameters:
  parameters - Parameters, rendering hints and coordinate reference system to use. The sample dimensions for each band in the destination image, or null if unknow.
See Also:   OperationJAI.deriveCategory
See Also:   OperationJAI.deriveUnit

 if (units[0]!=null && units[1]!=null) {
 return units[0].
Unit.multiply(Unit) multiply (units[1]);
 } else {
 return super.deriveUnit(units, cs, parameters);
 }
 

1. Converts source grid coverages to their geophysics view using (true). This allow to performs all computation on geophysics values instead of encoded samples. Note: this step is disabled if OperationJAI.computeOnGeophysicsValues computeOnGeophysicsValues returns false .
2. Ensures that every sources GridCoverage2D s use the same coordinate reference system (at least for the two-dimensional part) with the same GridGeometry2D.getGridToCRS2D gridToCRS relationship.
3. Invokes OperationJAI.deriveGridCoverage . The sources in the ParameterBlock are RenderedImage objects obtained from GridCoverage2D.getRenderedImage .
4. If a changes from non-geophysics to geophysics view were performed at step 1, converts the result back to the original view using (false).

Note: it would be possible to use ImagingParameters.parameters directly in some occasions. However, we peform an unconditional copy instead because some operations (e.g. "GradientMagnitude") may change the values.
Parameters:
  parameters - The ParameterValueGroup to be copied. A copy of the provided ParameterValueGroup as a JAI block.
since:
   2.4

Subclasses should override this method if they want to specify target and different than the default ones. For example if a subclass wants to force all images to be referenced in a CRS, then it may overrides this method as below:

 protected void resampleToCommonGeometry(...) {
 crs2D = DefaultGeographicCRS.WGS84;
 super.resampleToCommonGeometry(sources, crs2D, gridToCrs2D, hints);
 }