Bunch of little fixes this morning!

1. The guideline calculations for translating across lines was fixed. It was off if the scale was changed.
2. Transparent pixels were coming in black. Fixed that in the Image Grids. Now only color blocks will be clickable. I should make it possible to make inverse patterns.
That would be an interesting feature. Not sure how many people would use it.
3. The bounding box for masked items brought back from the canvas was not showing position correctly. That was fixed.