add Math.round() to Pixel.correctLevel()

The old versions of setRed/Green/Blue cast doubles to ints whenever
necessary. I thought the new versions would, but they actually didn't
because they passed the values through Pixel.correctLevel(int). I
assumed Jython would downcast the doubles to ints, but that was wrong.

So, I added a Pixel.correctLevel(double) that rounds the value passed
in before passing it to Pixel.correctLevel(int).

jes/java/Pixel.java

@@ -42,6 +42,17 @@ public static void setWrapLevels (boolean wrap) {
         wrapLevels = wrap;
     }
 
+    /**
+     * Round and correct a color level to be within 0 and 255,
+     * according to the current wrapLevels setting.
+     *
+     * @param level The user-provided level.
+     * @return A value within 0 and 255.
+     */
+    public static int correctLevel (double level) {
+        return correctLevel((int) Math.round(level));
+    }
+
     /**
      * Correct a color level to be within 0 and 255,
      * according to the current wrapLevels setting.