You could also go with this:

public void doSomething(int input)
{
   while(TransformInSomeWay(input), !ProcessingComplete(input))
   {
      DoSomethingElseTo(input);
   }
}

Or less confusingly:

bool TransformAndCheckCompletion(int &input)
{
   TransformInSomeWay(input);
   return ProcessingComplete(input))
}

public void doSomething(int input)
{
   while(TransformAndCheckCompletion(input))
   {
      DoSomethingElseTo(input);
   }
}

You could also go with this:

public void doSomething(int input)
{
   while(TransformInSomeWay(input), !ProcessingComplete(input))
   {
      DoSomethingElseTo(input);
   }
}

Or less confusingly:

bool TransformAndCheckCompletion(int &input)
{
   TransformInSomeWay(input);
   return ProcessingComplete(input))
}

public void doSomething(int input)
{
   while(TransformAndCheckCompletion(input))
   {
      DoSomethingElseTo(input);
   }
}