--- old/src/java.desktop/share/classes/com/sun/imageio/plugins/png/PNGMetadata.java	2018-03-28 08:05:21.938925001 +0530
+++ new/src/java.desktop/share/classes/com/sun/imageio/plugins/png/PNGMetadata.java	2018-03-28 08:05:21.698925001 +0530
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 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
@@ -268,7 +268,7 @@
     // If external (non-PNG sourced) data has red = green = blue,
     // always store it as gray and promote when writing
     public boolean tRNS_present;
-    public int tRNS_colorType; // PNG_COLOR_GRAY, _RGB, or _PALETTE
+    public int tRNS_colorType = -1; // PNG_COLOR_GRAY, _RGB, or _PALETTE
     public byte[] tRNS_alpha; // May have fewer entries than PLTE_red, etc.
     public int tRNS_gray;
     public int tRNS_red;