WIP: Add converters for all common image types

[CTR: There is one failing test... due to how SingleInputPreprocessors
work. They eagerly try to convert. Now that this commit adds so many
converters, we get a situation where e.g. the ActiveDatasetPreprocessor
takes precedence over the ActiveImageDisplayPreprocessor when filling
single ImageDisplay parameters, which is obviously bad... blargh.]

This work is a major step toward resolving imagej/imagej-legacy#229,
but does not quite do the entire job, since ij.ImagePlus is another
image type on that list, which is not available from imagej-common.
But we can add converters to imagej-legacy for ImagePlus to+from all
other image types, and then we'll have everything covered.

See also imagej/imagej-ops#54.

src/main/java/net/imagej/DefaultDatasetService.java

@@ -44,7 +44,6 @@
 import net.imglib2.converter.Converters;
 import net.imglib2.img.Img;
 import net.imglib2.img.ImgFactory;
-import net.imglib2.img.ImgView;
 import net.imglib2.img.cell.CellImgFactory;
 import net.imglib2.img.planar.PlanarImgFactory;
 import net.imglib2.type.NativeType;
@@ -62,7 +61,6 @@
 import net.imglib2.type.numeric.integer.UnsignedShortType;
 import net.imglib2.type.numeric.real.DoubleType;
 import net.imglib2.type.numeric.real.FloatType;
-import net.imglib2.util.Util;
 
 import net.imglib2.view.Views;
 import org.scijava.log.LogService;
@@ -228,7 +226,7 @@ private Dataset createARGBType(ImgPlus<ARGBType> imgPlus) {
 	public <T extends Type<T>> Dataset create(
 			final RandomAccessibleInterval<T> rai)
 	{
-		return create(wrapToImgPlus(rai));
+		return create(ImgPlus.wrap(rai));
 	}
 
 	private ImgPlus< UnsignedByteType > argbToMultiChannel(
@@ -239,7 +237,7 @@ private ImgPlus< UnsignedByteType > argbToMultiChannel(
 				.argbChannel(rai, 1);
 		RandomAccessibleInterval<UnsignedByteType> green = Converters.argbChannel(rai, 2);
 		RandomAccessibleInterval<UnsignedByteType> blue = Converters.argbChannel(rai, 3);
-		Img<UnsignedByteType> channels = wrapToImg(Views.stack(red, green, blue));
+		Img<UnsignedByteType> channels = ImgPlus.wrapToImg(Views.stack(red, green, blue));
 		int n = imgPlus.numDimensions();
 		CalibratedAxis[] axes = new CalibratedAxis[n + 1];
 		for (int d = 0; d < n; d++) axes[d] = imgPlus.axis(d);
@@ -346,25 +344,4 @@ private void invalidParams(final int bitsPerPixel, final boolean signed,
 		throw new IllegalArgumentException("Invalid parameters: bitsPerPixel=" +
 			bitsPerPixel + ", signed=" + signed + ", floating=" + floating);
 	}
-
-	private <T extends Type<T>> ImgPlus<T> wrapToImgPlus(
-		final RandomAccessibleInterval<T> rai)
-	{
-		if (rai instanceof ImgPlus) return (ImgPlus<T>) rai;
-		return new ImgPlus<>(wrapToImg(rai));
-	}
-
-	private <T extends Type<T>> Img<T> wrapToImg(
-		final RandomAccessibleInterval<T> rai)
-	{
-		if (rai instanceof Img) return (Img<T>) rai;
-		return ImgView.wrap(rai, imgFactory(rai));
-	}
-
-	private <T> ImgFactory<T> imgFactory(
-		final RandomAccessibleInterval<T> rai)
-	{
-		final T type = Util.getTypeFromInterval(rai);
-		return Util.getSuitableImgFactory(rai, type);
-	}
 }

src/main/java/net/imagej/ImgPlus.java

@@ -45,12 +45,16 @@
 import net.imglib2.Interval;
 import net.imglib2.Positionable;
 import net.imglib2.RandomAccess;
+import net.imglib2.RandomAccessibleInterval;
 import net.imglib2.RealPositionable;
 import net.imglib2.display.ColorTable;
 import net.imglib2.img.Img;
 import net.imglib2.img.ImgFactory;
+import net.imglib2.img.ImgView;
 import net.imglib2.img.WrappedImg;
 import net.imglib2.img.array.ArrayImg;
+import net.imglib2.type.Type;
+import net.imglib2.util.Util;
 
 /**
  * A simple container for storing an {@link Img} together with its metadata.
@@ -68,6 +72,33 @@ public class ImgPlus<T> extends AbstractCalibratedRealInterval<CalibratedAxis>
 	implements Img<T>, WrappedImg<T>, ImgPlusMetadata
 {
 
+	/** Wraps a {@link RandomAccessibleInterval} into an {@link ImgPlus}. */
+	public static <T extends Type<T>> ImgPlus<T> wrap(
+		final RandomAccessibleInterval<T> rai)
+	{
+		if (rai instanceof ImgPlus) return (ImgPlus<T>) rai;
+		return new ImgPlus<>(wrapToImg(rai));
+	}
+
+	/** Wraps a {@link RandomAccessibleInterval} into an {@link Img}. */
+	public static <T extends Type<T>> Img<T> wrapToImg(
+		final RandomAccessibleInterval<T> rai)
+	{
+		if (rai instanceof Img) return (Img<T>) rai;
+		return ImgView.wrap(rai, imgFactory(rai));
+	}
+
+	/**
+	 * Gets an {@link ImgFactory} suitable for creating {@link Img}s of the given
+	 * {@link RandomAccessibleInterval}'s container, type, and dimensions.
+	 */
+	public static <T> ImgFactory<T> imgFactory(
+		final RandomAccessibleInterval<T> rai)
+	{
+		final T type = Util.getTypeFromInterval(rai);
+		return Util.getSuitableImgFactory(rai, type);
+	}
+
 	private final Img<T> img;
 
 	private String name;