Revise, clean up, add javadoc.

* BdvN5Format doesn't have to extend N5Properties.
  Added DefaultN5Properties instead.

* 5D container slicing happens by overriding the (now exposed)
  N5ImageLoader.prepareCachedImage(...) method.

* N5ImageLoader.prefetch() must be called by the client if desired.
  This will open a N5Reader if necessary, so can happen independent of
  N5ImageLoader.open().

src/main/java/bdv/export/n5/WriteSequenceToN5.java

@@ -59,9 +59,7 @@
 import bdv.export.ProgressWriterNull;
 import bdv.export.SubTaskProgressWriter;
 import bdv.img.cache.SimpleCacheArrayLoader;
-import bdv.img.n5.BdvN5Format;
 import bdv.img.n5.N5ImageLoader;
-import bdv.img.n5.N5Properties;
 import mpicbg.spim.data.generic.sequence.AbstractSequenceDescription;
 import mpicbg.spim.data.generic.sequence.BasicImgLoader;
 import mpicbg.spim.data.generic.sequence.BasicSetupImgLoader;
@@ -276,7 +274,6 @@ static class N5DatasetIO< T extends RealType< T > & NativeType< T > > implements
 		private final int timepointId;
 		private final DataType dataType;
 		private final T type;
-		private final N5Properties n5Properties = new BdvN5Format();
 
 		public N5DatasetIO( final N5Writer n5, final Compression compression, final int setupId, final int timepointId, final T type )
 		{
@@ -338,7 +335,7 @@ public RandomAccessibleInterval< T > getImage( final int level ) throws IOExcept
 			final long[] dimensions = attributes.getDimensions();
 			final int[] cellDimensions = attributes.getBlockSize();
 			final CellGrid grid = new CellGrid( dimensions, cellDimensions );
-			final SimpleCacheArrayLoader< ? > cacheArrayLoader = N5ImageLoader.createCacheArrayLoader( n5Properties, n5, pathName );
+			final SimpleCacheArrayLoader< ? > cacheArrayLoader = N5ImageLoader.createCacheArrayLoader( n5, pathName );
 			return new ReadOnlyCachedCellImgFactory().createWithCacheLoader(
 					dimensions, type,
 					key -> {

src/main/java/bdv/img/n5/BdvN5Format.java

@@ -28,68 +28,11 @@
  */
 package bdv.img.n5;
 
-import org.janelia.saalfeldlab.n5.DataType;
-import org.janelia.saalfeldlab.n5.DatasetAttributes;
-import org.janelia.saalfeldlab.n5.N5Reader;
-
-import bdv.img.cache.VolatileCachedCellImg;
-import net.imglib2.RandomAccessibleInterval;
-import net.imglib2.type.NativeType;
-
-public class BdvN5Format implements N5Properties
+public class BdvN5Format
 {
 	public static final String DOWNSAMPLING_FACTORS_KEY = "downsamplingFactors";
 	public static final String DATA_TYPE_KEY = "dataType";
 
-	@Override
-	public String getPath( final int setupId )
-	{
-		return getPathName( setupId );
-	}
-
-	@Override
-	public String getPath( final int setupId, final int timepointId)
-	{
-		return getPathName( setupId, timepointId );
-	}
-
-	@Override
-	public String getPath( final int setupId, final int timepointId, final int level)
-	{
-		return getPathName( setupId, timepointId, level );
-	}
-
-	@Override
-	public DataType getDataType( final N5Reader n5, final int setupId )
-	{
-		// optionally cached as defined by N5ImageLoader.preFetchDatasetAttributes
-		return n5.getAttribute( getPath( setupId ), DATA_TYPE_KEY, DataType.class );
-	}
-
-	@Override
-	public double[][] getMipmapResolutions( final N5Reader n5, final int setupId )
-	{
-		// optionally cached as defined by N5ImageLoader.preFetchDatasetAttributes
-		return n5.getAttribute( getPath( setupId ), DOWNSAMPLING_FACTORS_KEY, double[][].class );
-	}
-
-	@Override
-	public DatasetAttributes getDatasetAttributes( final N5Reader n5, final String pathName )
-	{
-		// optionally cached as defined by N5ImageLoader.preFetchDatasetAttributes
-		return n5.getDatasetAttributes( pathName );
-	}
-
-	@Override
-	public <T extends NativeType<T>> RandomAccessibleInterval<T> extractImg(
-			final VolatileCachedCellImg<T, ?> img,
-			final int setupId,
-			final int timepointId)
-	{
-		return img;
-	}
-
-	// left the old code for compatibility 
 	public static String getPathName( final int setupId )
 	{
 		return String.format( "setup%d", setupId );

src/main/java/bdv/img/n5/DefaultN5Properties.java

@@ -0,0 +1,62 @@
+/*-
+ * #%L
+ * BigDataViewer core classes with minimal dependencies.
+ * %%
+ * Copyright (C) 2012 - 2024 BigDataViewer developers.
+ * %%
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ * #L%
+ */
+package bdv.img.n5;
+
+import org.janelia.saalfeldlab.n5.DataType;
+import org.janelia.saalfeldlab.n5.N5Reader;
+
+public class DefaultN5Properties implements N5Properties
+{
+	@Override
+	public String getDatasetPath( final int setupId, final int timepointId, final int level )
+	{
+		return BdvN5Format.getPathName( setupId, timepointId, level );
+	}
+
+	@Override
+	public DataType getDataType( final N5Reader n5, final int setupId )
+	{
+		final String path = BdvN5Format.getPathName( setupId );
+		return n5.getAttribute( path, BdvN5Format.DATA_TYPE_KEY, DataType.class );
+	}
+
+	@Override
+	public double[][] getMipmapResolutions( final N5Reader n5, final int setupId )
+	{
+		final String path = BdvN5Format.getPathName( setupId );
+		return n5.getAttribute( path, BdvN5Format.DOWNSAMPLING_FACTORS_KEY, double[][].class );
+	}
+
+	@Override
+	public long[] getDimensions( final N5Reader n5, final int setupId, final int timepointId, final int level  )
+	{
+		final String path = getDatasetPath( setupId, timepointId, level );
+		return n5.getDatasetAttributes( path ).getDimensions();
+	}
+}