--- 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]];
                             }
                         }