public int getBitShift() {
            if (!bitShiftSet) {
                throw new IllegalStateException(PropertyUtil.getString("PNGEncodeParam8"));
            }
            return bitShift;
        }
Returns the desired bit shift for a grayscale image.

<p> If the bit shift has not previously been set, or has been
unset, an <code>IllegalStateException</code> will be thrown.

@throws IllegalStateException if the bit shift is not set.
plugins/svg-plugin/batik-codec-fix/src/main/java/org/apache/batik/ext/awt/image/codec/png/PNGEncodeParam.java