Three state vs background image

Signwriter doesn't use background image in a three state setting.

The problem is in the signwriter_create_image() function, it should collect and merge all three background images in the for(), instead it looks for a $image->bgimage[$idx] before the for() where $idx is not defined yet.

Besides, the image ends up being transparent, when transparent is actually turned off. X offset doesn't happen either.

Thanks