Using batch convert/automatic crop with transparent backgrounds

[mikecode]

I have a bunch of 400x400 images that I potentially need to crop, if they have extra white space. `RPGCharacter-12.png` is an example of a file that should be cropped. `PixelGrad-01.png` should not be cropped as there is no transparent space around it. I'm unsure of the best way to proceed. When I choose the Automatic Crop action, I can use either the pixel color from one corner or a specified color. The result files attached are from the first option. The RPG character (and most others) came out perfect! The unintended consequence with the gradient file is that it removes the top ~50 pixels. It seems like specifying a "color" would be better but there doesn't seem to be a way to choose "transparent" here. Any advice?

I'm using XnViewMP Mac OSX Version 0.97.1

Thanks!

[xnview]

you can choose black as color