Extract NDVI value from raster

You have to be more specific. What type of feature do you need to extract.

One way would be to use two RasterCellValueReplacers one for values <-1 and one for values >1 and replace them by some value that you set as NoData via RasterBandNodataSetter. -32768 is one of the commonly used values as it is the lowest 16bit signed integer.

You can then use RasterExtentsCoercer to get Data Extents in a polygon or just style the raster accordingly in your software of choice.

Or use RasterStatisticsCalculator to extract some other data that you might need.

Please specify your desired end result.