--- /dev/null	2018-04-13 12:23:36.988791000 +0530
+++ new/test/jdk/javax/imageio/plugins/png/ReadPngGrayImageWithTRNSChunk.java	2018-04-13 12:29:30.519961000 +0530
@@ -0,0 +1,159 @@
+/*
+ * 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     6788458
+ * @summary Test verifies that PNGImageReader takes tRNS chunk values
+ *          into consideration while reading non-indexed Gray PNG images.
+ * @run     main ReadPngGrayImageWithTRNSChunk
+ */
+
+import java.awt.Graphics2D;
+import java.awt.image.BufferedImage;
+import java.awt.Color;
+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 ReadPngGrayImageWithTRNSChunk {
+
+    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 = 2;
+        int height = 1;
+        img = new BufferedImage(width, height, type);
+        Graphics2D g2D = img.createGraphics();
+
+        // transparent first pixel
+        g2D.setColor(new Color(255, 255, 255));
+        g2D.fillRect(0, 0, 1, 1);
+        // non-transparent second pixel
+        g2D.setColor(new Color(128, 128,128));
+        g2D.fillRect(1, 0, 1, 1);
+        g2D.dispose();
+
+        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 boolean verifyAlphaValue(BufferedImage img) {
+        Color firstPixel = new Color(img.getRGB(0, 0), true);
+        Color secondPixel = new Color(img.getRGB(1, 0), true);
+
+        return firstPixel.getAlpha() != 0 ||
+        secondPixel.getAlpha() != 255;
+    }
+
+    private static boolean read8BitGrayPNGWithTRNSChunk() throws IOException {
+        initialize(BufferedImage.TYPE_BYTE_GRAY);
+        // Create tRNS node and merge it with default metadata
+        createTRNSNode("255");
+
+        writeImage();
+
+        InputStream input= new ByteArrayInputStream(imageByteArray);
+        // Read 8 bit PNG Gray image with tRNS chunk
+        BufferedImage verify_img = ImageIO.read(input);
+        input.close();
+        // Verify alpha values present in first & second pixel
+        return verifyAlphaValue(verify_img);
+    }
+
+    private static boolean read16BitGrayPNGWithTRNSChunk() throws IOException {
+        initialize(BufferedImage.TYPE_USHORT_GRAY);
+        // Create tRNS node and merge it with default metadata
+        createTRNSNode("65535");
+
+        writeImage();
+
+        InputStream input= new ByteArrayInputStream(imageByteArray);
+        // Read 16 bit PNG Gray image with tRNS chunk
+        BufferedImage verify_img = ImageIO.read(input);
+        input.close();
+        // Verify alpha values present in first & second pixel
+        return verifyAlphaValue(verify_img);
+    }
+
+    public static void main(String[] args) throws IOException {
+        boolean read8BitFail, read16BitFail;
+        // read 8 bit PNG Gray image with tRNS chunk
+        read8BitFail = read8BitGrayPNGWithTRNSChunk();
+
+        // read 16 bit PNG Gray image with tRNS chunk
+        read16BitFail = read16BitGrayPNGWithTRNSChunk();
+
+        if (read8BitFail || read16BitFail) {
+            throw new RuntimeException("PNGImageReader is not using" +
+            " transparent pixel information from tRNS chunk properly");
+        }
+    }
+}
+