Non-rectangular raster clipping

From Fmepedia

FME 2008 could not clip rasters with non-rectangular clippers such as arbitrary polygons. FME 2009 includes non-rectangular clipping capabilities into the standard Clipper transformer.

The first version of the workspace was based on rasterizing of the clipping polygons and mosaicking, but after we added VectorOnRasterOverlayer transformer, achieving the same result became much easier. We simply can use the raster bounding box as an outer boundary of a donut, and the vector polygon - as an inner boundary. After that we overlay the donut over the raster. As simple as this - check the new workspace.

We decided to keep the old workspace because its technique definitely can be use for some other raster/vector manipulations.

Here is the the raster used as a source in the examples.

Note that the resulting image has the same pixel size as the original - only content of the raster is being clipped.

I must add that a question from our user group FME Talk (http://groups.google.com/group/fmetalk/browse_thread/thread/bc008f75aa239a9f) helped us to investigate once again the question of vector to raster overlay and find that we have this wonderful VectorOnRasterOverlayer. Here is another workspace showing how to overlay a vector polygon on the raster background. The only difference with the workspace above - it does not create the donut.

Check this example for other use of this transformer.

As an unexpected side effect was discovered when a wavelet compression format is used as destination (not used in the attached example) a new direction in FME Art Movement