let shape = null;
let centerX = (this.state.startX + this.state.endX) / 2;
let centerY = (this.state.startY + this.state.endY) / 2;
let width = Math.abs(this.state.endX - this.state.startX);
let height = Math.abs(this.state.endY - this.state.startY);
shape =<Paper.Rectangle center={[centerX, centerY]} size={[width, height]} strokeWidth={4} strokeColor={'#ff0000'} />

return (
<div>
	<Paper.View ref={(view) => { this.view = view; }} {...viewProps}>
		{shape}
	</Paper.View>
</div>
);