code: protected Double getBicubicInterpolationValue(Double[][] values,
  			CoverageDataSourcePixel sourcePixelX,
  			CoverageDataSourcePixel sourcePixelY) {
  		return getBicubicInterpolationValue(values, sourcePixelX.getOffset(),
  				sourcePixelY.getOffset());
  	}
docs: Get the bicubic interpolation coverage data value from the 4 x 4 coverage
  data values
  
  @param values
  coverage data values
  @param sourcePixelX
  source pixel x
  @param sourcePixelY
  source pixel y
  @return bicubic coverage data value