Get Bounding Layer for Rotated Layer

getBoundingLayerForRotatedLayer.coffee

getBoundingLayerForRotatedLayer = (layer) ->
	tr = "topRight"; bl = "bottomLeft"; tl = "topLeft"; br = "bottomRight";
	center   = x: layer.midX,  y: layer.midY
	size     = w: layer.width, h: layer.height
	rotation = layer.rotation
	corners  = 
		"#{tr}": x:  (size.w/2), y:  (size.h/2)
		"#{bl}": x: -(size.w/2), y: -(size.h/2)
	
	getRotatedPoint = (p) ->
		return {
			x: center.x + (p.x  * Math.cos rotation) - (p.y * Math.sin rotation)
			y: center.y + (p.x  * Math.sin rotation) - (p.y * Math.cos rotation)
		}
	
	calculateFrameFromOppositePoints = (op) ->
		cornerPoints = "#{tl}": null, "#{bl}": null, "#{tr}": null, "#{br}": null
		# Update with opposite points
		cornerPoints[label] = point for label, point of op
		# Fill in Missing Points
		for label, point of cornerPoints when not point?
			cornerPoints[label] = 
				x: cornerPoints[(if label is tl then bl else tr)].x
				y: cornerPoints[(if label is br then bl else tr)].y
		# Return Frame calculated from all points
		return {
			x:      cornerPoints[tl].x,
			y:      cornerPoints[tl].y,
			width:  cornerPoints[tr].x - cornerPoints[tl].x,
			height: cornerPoints[bl].y - cornerPoints[tl].y
		}

	# Get Rotated Point for Two corners
	corners[corner] = getRotatedPoint point for corner, point of corners
	# Return layer with frame applied
	return new Layer parent: layer.parent, visible: false, frame: calculateFrameFromOppositePoints corners

Give it a rotated layer and get a layer back that is a bounding Box for the original layer.