annatation format标注格式

[xiyufeng2]

the annotation[x,y,w,h,0]，how to define the w and h? Is theta the angle between the edge and the positive direction of X axis？which edge？
如何定义W和H？theta表示与x轴的锐角，变化范围为[-90,0),这里是x轴正方向吗？感谢