Fix min/max String Exception bug

src/main/java/net/imagej/ops/image/ascii/DefaultASCII.java

@@ -36,6 +36,7 @@
 import net.imglib2.Cursor;
 import net.imglib2.IterableInterval;
 import net.imglib2.type.numeric.RealType;
+import net.imglib2.type.numeric.real.DoubleType;
 import net.imglib2.util.Pair;
 
 import org.scijava.plugin.Parameter;
@@ -46,7 +47,7 @@
  * <p>
  * Only the first two dimensions of the image are considered.
  * </p>
- * 
+ *
  * @author Curtis Rueden
  */
 @Plugin(type = Ops.Image.ASCII.class)
@@ -79,47 +80,50 @@ public String calculate(final IterableInterval<T> input) {
 			if (min == null) min = minMax.getA();
 			if (max == null) max = minMax.getB();
 		}
-		return ascii(input, min, max);
+
+		DoubleType minSource = new DoubleType(min.getRealDouble());
+		DoubleType maxSource = new DoubleType(max.getRealDouble());
+		DoubleType minTarget = new DoubleType(0);
+		DoubleType maxTarget = new DoubleType(CHARS.length());
+
+		IterableInterval<DoubleType> converted = ops().convert().float64(input);
+		IterableInterval<DoubleType> normalized = ops().image().normalize(converted,
+			minSource, maxSource, minTarget, maxTarget);
+
+		return ascii(normalized);
 	}
 
 	// -- Utility methods --
 
-	public static <T extends RealType<T>> String ascii(
-		final IterableInterval<T> image, final T min, final T max)
-	{
+	public static String ascii(final IterableInterval<DoubleType> image) {
 		final long dim0 = image.dimension(0);
 		final long dim1 = image.dimension(1);
-		// TODO: Check bounds.
+
 		final int w = (int) (dim0 + 1);
 		final int h = (int) dim1;
 
-		// span = max - min
-		final T span = max.copy();
-		span.sub(min);
-
 		// allocate ASCII character array
 		final char[] c = new char[w * h];
 		for (int y = 1; y <= h; y++) {
 			c[w * y - 1] = '\n'; // end of row
 		}
 
 		// loop over all available positions
-		final Cursor<T> cursor = image.localizingCursor();
+		final Cursor<DoubleType> cursor = image.localizingCursor();
 		final int[] pos = new int[image.numDimensions()];
-		final T tmp = image.firstElement().copy();
 		while (cursor.hasNext()) {
 			cursor.fwd();
 			cursor.localize(pos);
 			final int index = w * pos[1] + pos[0];
 
-			// normalized = (value - min) / (max - min)
-			tmp.set(cursor.get());
-			tmp.sub(min);
-			final double normalized = tmp.getRealDouble() / span.getRealDouble();
-
-			final int charLen = CHARS.length();
-			final int charIndex = (int) (charLen * normalized);
-			c[index] = CHARS.charAt(charIndex < charLen ? charIndex : charLen - 1);
+			// grab the value from the normalized image, convert it to an ASCII char.
+			// N.B. if the original value was at the max for the type range it will be
+			// equal to the length of the char array after normalization. Thus to
+			// prevent an exception when converting to ASCII we subtract one when the
+			// normalized image value is equal to the length.
+			int val = (int) cursor.get().getRealDouble();
+			if (val == CHARS.length()) val--;
+			c[index] = CHARS.charAt(val);
 		}
 
 		return new String(c);

src/test/java/net/imagej/ops/image/ascii/ASCIITest.java

@@ -29,7 +29,7 @@
 
 package net.imagej.ops.image.ascii;
 
-import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertEquals;
 
 import net.imagej.ops.AbstractOpTest;
 import net.imglib2.img.Img;
@@ -40,8 +40,9 @@
 
 /**
  * Tests {@link net.imagej.ops.Ops.Image.ASCII}.
- * 
+ *
  * @author Leon Yang
+ * @author Gabe Selzer
  */
 public class ASCIITest extends AbstractOpTest {
 
@@ -63,9 +64,41 @@ public void testDefaultASCII() {
 		final String ascii = (String) ops.run(DefaultASCII.class, img);
 		for (int i = 0; i < len; i++) {
 			for (int j = 0; j < width; j++) {
-				assertTrue(ascii.charAt(i * (width + 1) + j) == CHARS.charAt(i));
+				assertEquals(ascii.charAt(i * (width + 1) + j), CHARS.charAt(i));
 			}
-			assertTrue(ascii.charAt(i * (width + 1) + width) == '\n');
+			assertEquals(ascii.charAt(i * (width + 1) + width), '\n');
 		}
 	}
+
+	@Test
+	public void testASCIIMinMax() {
+		// character set used in DefaultASCII, could be updated if necessary
+		final String CHARS = "#O*o+-,. ";
+		final int len = CHARS.length();
+		final int width = 10;
+		final byte[] array = new byte[width * len];
+		for (int i = 0; i < len; i++) {
+			for (int j = 0; j < width; j++) {
+				array[i * width + j] = (byte) (i * width + j);
+			}
+		}
+		final UnsignedByteType min = new UnsignedByteType(0);
+		final UnsignedByteType max = new UnsignedByteType(90);
+		final Img<UnsignedByteType> img = ArrayImgs.unsignedBytes(array, width,
+			len);
+		final String ascii = (String) ops.run(DefaultASCII.class, img, min, max);
+		for (int i = 0; i < len; i++) {
+			for (int j = 0; j < width; j++) {
+				assertEquals(ascii.charAt(i * (width + 1) + j), CHARS.charAt(i));
+			}
+			assertEquals(ascii.charAt(i * (width + 1) + width), '\n');
+		}
+
+		// make sure that the values of the min/max ascii are the same as the
+		// unclamped version (which will set the minimum and maximum to those of the
+		// data, which are the same as the ones that we set).
+		final String asciiUnclamped = (String) ops.run(DefaultASCII.class, img);
+		assertEquals(asciiUnclamped, ascii);
+
+	}
 }