Merge pull request #429 from ikhaldeev/fix-extra-samples-alpha

Fix getAlphaRaster for ExtraSamplesColorModel (TIFFImageReader)

imageio/imageio-tiff/src/main/java/com/twelvemonkeys/imageio/plugins/tiff/ExtraSamplesColorModel.java

@@ -7,6 +7,7 @@ import java.awt.color.ColorSpace;
 import java.awt.image.ComponentColorModel;
 import java.awt.image.ComponentSampleModel;
 import java.awt.image.SampleModel;
+import java.awt.image.WritableRaster;
 
 /**
  * ExtraSamplesColorModel.
@@ -41,4 +42,19 @@ final class ExtraSamplesColorModel extends ComponentColorModel {
         // Must have the same number of components
         return numComponents == sm.getNumBands() && transferType == sm.getTransferType();
     }
+
+    @Override
+    public WritableRaster getAlphaRaster(WritableRaster raster) {
+        if (hasAlpha() == false) {
+            return null;
+        }
+
+        int x = raster.getMinX();
+        int y = raster.getMinY();
+        int[] band = new int[1];
+        band[0] = super.getNumComponents() - 1;
+        return raster.createWritableChild(x, y, raster.getWidth(),
+                raster.getHeight(), x, y,
+                band);
+    }
 }

imageio/imageio-tiff/src/test/java/com/twelvemonkeys/imageio/plugins/tiff/TIFFImageReaderTest.java

@@ -40,6 +40,7 @@ import javax.imageio.stream.ImageInputStream;
 import java.awt.*;
 import java.awt.image.BufferedImage;
 import java.awt.image.Raster;
+import java.awt.image.WritableRaster;
 import java.io.IOException;
 import java.nio.ByteOrder;
 import java.util.Arrays;
@@ -586,6 +587,25 @@ public class TIFFImageReaderTest extends ImageReaderAbstractTest<TIFFImageReader
         }
     }
 
+    @Test
+    public void testAlphaRasterForMultipleExtraSamples() throws IOException {
+        ImageReader reader = createReader();
+        try (ImageInputStream stream = ImageIO.createImageInputStream(getClassLoaderResource("/tiff/extra-channels.tif"))) {
+            reader.setInput(stream);
+
+            BufferedImage image = reader.read(0);
+            assertNotNull(image);
+
+            assertEquals(0x00, image.getRGB(0, 0));
+            assertEquals(0xf5, (image.getRGB(50, 50) & 0xff000000) >>> 24);
+
+            int[] alpha = new int[1];
+            WritableRaster alphaRaster = image.getAlphaRaster();
+            assertEquals(0x00, alphaRaster.getPixel(0, 0, alpha)[0]);
+            assertEquals(0xf5,  alphaRaster.getPixel(50, 50, alpha)[0]);
+        }
+    }
+
     @Test
     public void testReadWithSubsampleParamPixelsJPEG() throws IOException {
         // Tiled "new style" JPEG