--- a/src/java.desktop/share/classes/com/sun/imageio/plugins/png/PNGImageReader.java	Thu Nov 15 14:14:31 2018 -0800
+++ b/src/java.desktop/share/classes/com/sun/imageio/plugins/png/PNGImageReader.java	Tue Nov 20 14:37:24 2018 +0530
@@ -1163,8 +1163,7 @@
         // same bit depth as the source data
         boolean adjustBitDepths = false;
         int[] outputSampleSize = imRas.getSampleModel().getSampleSize();
-        int numBands = outputSampleSize.length;
-        for (int b = 0; b < numBands; b++) {
+        for (int b = 0; b < inputBands; b++) {
             if (outputSampleSize[b] != bitDepth) {
                 adjustBitDepths = true;
                 break;
@@ -1177,8 +1176,8 @@
         if (adjustBitDepths) {
             int maxInSample = (1 << bitDepth) - 1;
             int halfMaxInSample = maxInSample/2;
-            scale = new int[numBands][];
-            for (int b = 0; b < numBands; b++) {
+            scale = new int[inputBands][];
+            for (int b = 0; b < inputBands; b++) {
                 int maxOutSample = (1 << outputSampleSize[b]) - 1;
                 scale[b] = new int[maxInSample + 1];
                 for (int s = 0; s <= maxInSample; s++) {
@@ -1304,7 +1303,7 @@
 
                         passRow.getPixel(newSrcX, 0, ps);
                         if (adjustBitDepths) {
-                            for (int b = 0; b < numBands; b++) {
+                            for (int b = 0; b < inputBands; b++) {
                                 ps[b] = scale[b][ps[b]];
                             }
                         }

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/jdk/javax/imageio/plugins/png/VerifyBitDepthScalingWithTRNSChunk.java	Tue Nov 20 14:37:24 2018 +0530
@@ -0,0 +1,137 @@
+/*
+ * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug     8211795
+ * @summary Test verifies that PNGImageReader maintains proper
+ *          number of bands for scale array when PNG image
+ *          has tRNS chunk.
+ * @run     main VerifyBitDepthScalingWithTRNSChunk
+ */
+
+import java.awt.Graphics2D;
+import java.awt.image.BufferedImage;
+import java.awt.Color;
+import java.awt.image.IndexColorModel;
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Iterator;
+import javax.imageio.ImageTypeSpecifier;
+import javax.imageio.ImageWriter;
+import javax.imageio.ImageIO;
+import javax.imageio.ImageWriteParam;
+import javax.imageio.metadata.IIOInvalidTreeException;
+import javax.imageio.metadata.IIOMetadata;
+import javax.imageio.metadata.IIOMetadataNode;
+import javax.imageio.stream.ImageOutputStream;
+import javax.imageio.IIOImage;
+
+public class VerifyBitDepthScalingWithTRNSChunk {
+
+    private static BufferedImage img;
+    private static ImageWriter writer;
+    private static ImageWriteParam param;
+    private static IIOMetadata metadata;
+    private static byte[] imageByteArray;
+
+    private static void initialize(int type) {
+        int width = 1;
+        int height = 1;
+        // create Palette & IndexColorModel for bitdepth 1
+        int size = 2;
+        int bitDepth = 1;
+        byte[] r = new byte[size];
+        byte[] g = new byte[size];
+        byte[] b = new byte[size];
+
+        r[0] = g[0] = b[0] = 0;
+        r[1] = g[1] = b[1] = (byte)255;
+
+        IndexColorModel cm = new IndexColorModel(bitDepth, size, r, g, b);
+        img = new BufferedImage(width, height, type, cm);
+        Graphics2D g2D = img.createGraphics();
+        g2D.setColor(new Color(255, 255, 255));
+        g2D.fillRect(0, 0, width, height);
+
+        Iterator<ImageWriter> iterWriter =
+                ImageIO.getImageWritersBySuffix("png");
+        writer = iterWriter.next();
+
+        param = writer.getDefaultWriteParam();
+        ImageTypeSpecifier specifier =
+                ImageTypeSpecifier.
+                        createFromBufferedImageType(type);
+        metadata = writer.getDefaultImageMetadata(specifier, param);
+    }
+
+    private static void createTRNSNode(String tRNS_value)
+            throws IIOInvalidTreeException {
+        IIOMetadataNode tRNS_gray = new IIOMetadataNode("tRNS_Grayscale");
+        tRNS_gray.setAttribute("gray", tRNS_value);
+
+        IIOMetadataNode tRNS = new IIOMetadataNode("tRNS");
+        tRNS.appendChild(tRNS_gray);
+        IIOMetadataNode root = new IIOMetadataNode("javax_imageio_png_1.0");
+        root.appendChild(tRNS);
+        metadata.mergeTree("javax_imageio_png_1.0", root);
+    }
+
+    private static void writeImage() throws IOException {
+        ByteArrayOutputStream baos = new ByteArrayOutputStream();
+        ImageOutputStream ios = ImageIO.createImageOutputStream(baos);
+        writer.setOutput(ios);
+        writer.write(metadata, new IIOImage(img, null, metadata), param);
+        writer.dispose();
+
+        baos.flush();
+        imageByteArray = baos.toByteArray();
+        baos.close();
+    }
+
+    private static void verifyBitDepthScalingWithTRNSChunk()
+        throws IOException {
+        initialize(BufferedImage.TYPE_BYTE_BINARY);
+        // Create tRNS node with some value and merge it with default metadata
+        createTRNSNode("255");
+
+        writeImage();
+
+        InputStream input= new ByteArrayInputStream(imageByteArray);
+        /*
+         * Read 1 bit PNG Gray image with tRNS chunk.
+         * Since bitDepth is 1 there will be scaling of each channel,
+         * and it has tRNS chunk for which we will add extra alpha channel.
+         * This will result in creation of scale array in PNGImageReader.
+         */
+        ImageIO.read(input);
+        input.close();
+    }
+
+    public static void main(String[] args) throws IOException {
+        verifyBitDepthScalingWithTRNSChunk();
+    }
+}
+