Changing "canvas size", or Letterboxing

I have about 1100 thumbnail type images that are all 160px wide but of varying heights. I need to make all of them exactly 160w x 110h, retaining the aspect ratio of the original. Essentially what I need to do is make the "canvas" 160x110, and fit the original in that canvas.

The function I'm imagining is as such: If the original is taller than 110p, it shortens the image to 110h, preserving the aspect ratio, and padded both sides with white bars to fill out the blank width. If the original was shorter than 110h, white bars were put above and below the original to fill in that extra height, like letterboxing.

We accomplished this with a script to very good effect, except the shrunken images were of poor, grainy GIF-like quality compared to those I batch with Picture Resizer (which always look great).

Is there a way I can get this same effect with PhotoResize? Or perhaps someone knows of another script that uses PhotoResize's reduction algorithms?

Thanks!
Packy