Util: add method to convert images of RealType to double[]

Author: maarzt

src/main/java/net/imglib2/util/Util.java

@@ -45,18 +45,21 @@
 import net.imglib2.RealLocalizable;
 import net.imglib2.RealRandomAccess;
 import net.imglib2.RealRandomAccessible;
+import net.imglib2.img.Img;
 import net.imglib2.img.ImgFactory;
 import net.imglib2.img.array.ArrayImg;
 import net.imglib2.img.array.ArrayImgFactory;
 import net.imglib2.img.cell.CellImgFactory;
 import net.imglib2.img.list.ListImgFactory;
 import net.imglib2.type.NativeType;
 import net.imglib2.type.Type;
+import net.imglib2.type.numeric.RealType;
 import net.imglib2.type.operators.ValueEquals;
 import net.imglib2.view.Views;
 
 import java.util.List;
 import java.util.function.BiPredicate;
+import java.util.stream.StreamSupport;
 
 /**
  * A collection of general-purpose utility methods for working with ImgLib2 data
@@ -1003,4 +1006,30 @@ final static public void max( final double[] a, final double[] b )
 			if ( b[ i ] > a[ i ] )
 				a[ i ] = b[ i ];
 	}
+
+	/**
+	 * Returns the content of {@code Iterable<RealType>} as array of doubles.
+	 */
+	public static double[] asDoubleArray( Iterable< ? extends RealType< ? > > iterable )
+	{
+		return StreamSupport.stream( iterable.spliterator(), false ).mapToDouble( RealType::getRealDouble ).toArray();
+	}
+
+	/**
+	 * Returns the pixels of an RandomAccessibleInterval of RealType as array of doubles.
+	 * The pixels are sorted in flat iteration order.
+	 */
+	public static double[] asDoubleArray( RandomAccessibleInterval< ? extends RealType< ? > > rai )
+	{
+		return asDoubleArray( Views.flatIterable( rai ) );
+	}
+
+	/**
+	 * Returns the pixels of an image of RealType as array of doubles.
+	 * The pixels are sorted in flat iteration order.
+	 */
+	public static double[] asDoubleArray( Img< ? extends RealType< ? > > image )
+	{
+		return asDoubleArray( ( RandomAccessibleInterval< ? extends RealType< ? > > ) image );
+	}
 }

src/test/java/net/imglib2/util/UtilTest.java

@@ -34,10 +34,6 @@
 
 package net.imglib2.util;
 
-import static junit.framework.TestCase.assertFalse;
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertTrue;
-
 import net.imglib2.FinalInterval;
 import net.imglib2.RealLocalizable;
 import net.imglib2.RealPoint;
@@ -49,14 +45,18 @@
 import net.imglib2.img.list.ListImgFactory;
 import net.imglib2.type.logic.BitType;
 import net.imglib2.type.logic.BoolType;
-
 import net.imglib2.type.numeric.RealType;
 import net.imglib2.type.numeric.integer.IntType;
 import net.imglib2.type.numeric.real.DoubleType;
 import org.junit.Test;
 
 import java.util.function.BiPredicate;
 
+import static junit.framework.TestCase.assertFalse;
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
 public class UtilTest
 {
 
@@ -178,4 +178,13 @@ private Img<DoubleType > doublesImage( double... pixels )
 	{
 		return ArrayImgs.doubles( pixels, pixels.length );
 	}
+
+	@Test
+	public void testAsDoubleArray()
+	{
+		double[] expected = { 1, 2, 3, 4 };
+		Img< DoubleType > img = ArrayImgs.doubles( expected, 2, 2 );
+		double[] result = Util.asDoubleArray( img );
+		assertArrayEquals( expected, result, 0.0 );
+	}
 }