Whoops. Adding missing reset method.

imageio/imageio-core/src/main/java/com/twelvemonkeys/imageio/ImageWriterBase.java

@@ -77,6 +77,7 @@ public abstract class ImageWriterBase extends ImageWriter {
 
     @Override
     public void setOutput(final Object output) {
+        resetMembers();
         super.setOutput(output);
 
         if (output instanceof ImageOutputStream) {
@@ -95,6 +96,15 @@ public abstract class ImageWriterBase extends ImageWriter {
         }
     }
 
+    @Override
+    public void reset() {
+        super.reset();
+        resetMembers();
+    }
+
+    protected void resetMembers() {
+    }
+
     /**
      * Returns {@code null}
      *