Start Javadoc to note exception behavior.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/imaging/trunk@1535239 13f79535-47bb-0310-9956-ffa450edef68
Inline unused lvar.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/imaging/trunk@1535240 13f79535-47bb-0310-9956-ffa450edef68