message: inverted source fix
diff: @@ -104,7 +104,7 @@ abstract class LuminanceSource {
  * @return a wrapper of this {@code LuminanceSource} which inverts the luminances it returns -- black becomes
  * white and vice versa, and each value becomes (255-value).
  */
  - public abstract invert(): LuminanceSource;
  + public abstract invert(): InvertedLuminanceSource;
  /**
  * Returns a new object with rotated image data by 90 degrees counterclockwise.
  