Crop to content; i.e., ImageMagick -trim +repage

[StainlessStlRat]

I'm trying to remove the empty space around some of my PNG data (think a square inside of a rectangle shaped PNG, the sides could be trimmed off).

In GIMP you can do this with "Crop to content" and with ImageMagick you can use -trim +repage to achieve this.

Is there a way to do this with bimg I'm missing? I tried Trim() but no affect