Add Gauss3 1D kernel helper methods

Author: tpietzsch

src/main/java/net/imglib2/algorithm/gauss3/Gauss3.java

@@ -248,23 +248,28 @@ public static < S extends NumericType< S >, T extends NumericType< T > > void ga
 
 	public static double[][] halfkernels( final double[] sigma )
 	{
-		final int n = sigma.length;
-		final double[][] halfkernels = new double[ n ][];
-		final int[] size = halfkernelsizes( sigma );
-		for ( int i = 0; i < n; ++i )
-			halfkernels[ i ] = halfkernel( sigma[ i ], size[ i ], true );
+		final double[][] halfkernels = new double[ sigma.length ][];
+		Arrays.setAll( halfkernels, i -> halfkernel( sigma[ i ] ) );
 		return halfkernels;
 	}
 
 	public static int[] halfkernelsizes( final double[] sigma )
 	{
-		final int n = sigma.length;
-		final int[] size = new int[ n ];
-		for ( int i = 0; i < n; ++i )
-			size[ i ] = Math.max( 2, ( int ) ( 3 * sigma[ i ] + 0.5 ) + 1 );
+		final int[] size = new int[ sigma.length ];
+		Arrays.setAll( size, i -> halfkernelsize( sigma[ i ] ) );
 		return size;
 	}
 
+	public static int halfkernelsize( final double sigma )
+	{
+		return Math.max( 2, ( int ) ( 3 * sigma + 0.5 ) + 1 );
+	}
+
+	public static double[] halfkernel( final double sigma )
+	{
+		return halfkernel( sigma, halfkernelsize( sigma ), true );
+	}
+
 	/**
 	 * Returns a gaussian half kernel with the given sigma and size.
 	 * <p>