azavea/geotrellis — pull request #274 by joshmarcus (2012-12-17 15:21:14+00:00)
Title: Add analysis area support to focal operations

This pull request modifies the focal operation framework to support an optional analysis area. A focal operation with an analysis area only operates on the specifies analysis area, which is a region within the input raster, but can access the cells outside of the analysis area for calculating the value for each cell.

This is critical for data parallelization of focal operations -- as each processor needs to act on a specific area but have access to external data -- but is implemented in this way so as to minimally impact the focal operation framework.

Individual operations *could* be given an optional analysis area argument, but they have not been updated to include them. If an analysis area is not specified, the analysis area is the full extent of the input raster. An operation with an analysis area can be produced with the "analysisAreaOp" method.