Add utilities for converting Color Tables to LUTs

Author: gselzer

src/main/java/net/imglib2/imagej/ColorTableToLUT.java

@@ -0,0 +1,30 @@
+package net.imglib2.imagej;
+
+import ij.process.LUT;
+import net.imglib2.display.ColorTable;
+import net.imglib2.util.Binning;
+
+/**
+ * Provides convenience functions to convert ImgLib2 {@link ColorTable}s into
+ * ImageJ {@link LUT} objects.
+ *
+ *
+ * @author Gabriel Selzer
+ */
+public class ColorTableToLUT {
+
+    /**
+     * Copies the data from {@code table} into a new {@link LUT}
+     * @param table the {@link ColorTable} to convert
+     * @return a {@link LUT} containing the same color mapping as {@code table}
+     */
+    public static LUT convert(final ColorTable table) {
+        byte[][] data = new byte[3][256];
+        for (int bin = 0; bin < 256; bin++) {
+            data[ColorTable.RED][bin] = (byte) table.get(ColorTable.RED, bin);
+            data[ColorTable.GREEN][bin] = (byte) table.get(ColorTable.GREEN, bin);
+            data[ColorTable.BLUE][bin] = (byte) table.get(ColorTable.BLUE, bin);
+        }
+        return new LUT(data[ColorTable.RED], data[ColorTable.GREEN], data[ColorTable.BLUE]);
+    }
+}

src/main/java/net/imglib2/imagej/LUTToColorTable.java

@@ -11,13 +11,15 @@
  * {@link net.imglib2.display.ColorTable}s.
  *
  *
- * @author Stephan Preibisch
- * @author Stephan Saalfeld
- * @author Matthias Arzt
  * @author Gabriel Selzer
  */
 public class LUTToColorTable {
 
+    /**
+     * Wraps (i.e. copyless) {@code lut} into a {@link ColorTable}.
+     * @param lut the {@link LUT} to convert
+     * @return a {@link ColorTable} enclosing {@code lut}
+     */
     public static ColorTable wrap(final LUT lut) {
         return new ColorTable() {
             @Override

src/test/java/net/imglib2/imagej/ColorTableToLUTTest.java

@@ -0,0 +1,33 @@
+package net.imglib2.imagej;
+
+import ij.process.LUT;
+import net.imglib2.display.ColorTable;
+import net.imglib2.display.ColorTable8;
+import org.junit.Test;
+
+import java.util.Random;
+
+import static org.junit.Assert.assertEquals;
+
+public class ColorTableToLUTTest {
+
+    @Test
+    public void testConvertColorTable() {
+        Random r = new Random(0xdeadbeefL);
+        byte[] reds = new byte[256];
+        r.nextBytes(reds);
+        byte[] greens = new byte[256];
+        r.nextBytes(greens);
+        byte[] blues = new byte[256];
+        r.nextBytes(blues);
+        ColorTable table = new ColorTable8(reds, greens, blues);
+        LUT actual = ColorTableToLUT.convert(table);
+        for(int i = 0; i < 256; i++) {
+            // Note ColorTable.get unsigned bytes as ints
+            assertEquals(reds[i], (byte) actual.getRed(i));
+            assertEquals(greens[i], (byte) actual.getGreen(i));
+            assertEquals(blues[i], (byte) actual.getBlue(i));
+            assertEquals((byte) 255, (byte) actual.getAlpha(i));
+        }
+    }
+}

src/test/java/net/imglib2/imagej/LUTToColorTableTest.java

@@ -20,10 +20,10 @@ public void testWrapLUT() {
         Random r = new Random(0xdeadbeefL);
         byte[] reds = new byte[256];
         r.nextBytes(reds);
-        byte[] blues = new byte[256];
-        r.nextBytes(blues);
         byte[] greens = new byte[256];
         r.nextBytes(greens);
+        byte[] blues = new byte[256];
+        r.nextBytes(blues);
         LUT lut = new LUT(reds, greens, blues);
         ColorTable actual = LUTToColorTable.wrap(lut);
         assertEquals(256, actual.getLength());