OpenCV求两个矩形是否相交,以及他们的重叠度

在图像处理中经常会遇到判断两个矩形是否相交，以及相交的比例的情况，下面是来自TLD算法中源码的求法：

float bbOverlap(const BoundingBox& box1,const BoundingBox& box2)
{
  if (box1.x > box2.x+box2.width) { return 0.0; }
  if (box1.y > box2.y+box2.height) { return 0.0; }
  if (box1.x+box1.width < box2.x) { return 0.0; }
  if (box1.y+box1.height < box2.y) { return 0.0; }
  float colInt =  min(box1.x+box1.width,box2.x+box2.width) - max(box1.x, box2.x);
  float rowInt =  min(box1.y+box1.height,box2.y+box2.height) - max(box1.y,box2.y);
  float intersection = colInt * rowInt;
  float area1 = box1.width*box1.height;
  float area2 = box2.width*box2.height;
  return intersection / (area1 + area2 - intersection);
}