;Check if two bounding boxes intersect
;  input
;    bbox1 - 4 element array of ints, [left, bottom, right, top] describing a bbox
;    bbox2 - 4 element array of ints, describing the other bbox
;  return
;    1 if bboxes intersect, 0 otherwise
;
;  Translated from c code here
;bool Intersect(RECT* r3, const RECT * r1, const RECT * r2) {
;    bool fIntersect =  ( r2->left right
;                                && r2->right > r1->left
;                                && r2->top bottom
;                                && r2->bottom > r1->top
;                                ); 
;
;    if(fIntersect) {
;        SetRect(r3,
;                     max(r1->left, r2->left),
;                     max(r1->top, r2->top),
;                     min( r1->right, r2->right),
;                     min(r1->bottom, r2->bottom));
;    } else {
;        SetRect(r3, 0, 0, 0, 0);
;    }
;    return fIntersect;
;}
function find_bbox_intersect,bbox1,bbox2,is_intersect
  is_intersect=is_bbox_intersect(bbox1,bbox2)
  if is_intersect then begin
    return,[ $
             max([bbox1[0],bbox2[0]]), $
	     max([bbox1[1],bbox2[1]]), $
	     min([bbox1[2]-1,bbox2[2]-1]), $
	     min([bbox1[3]-1,bbox2[3]-1])  $
	   ]
  end else begin
    return,[0,0,0,0]
  end
end

function random_bbox,seed
  x1=fix(randomu(seed)*500)
  x2=fix(randomu(seed)*500)
  y1=fix(randomu(seed)*500)
  y2=fix(randomu(seed)*500)
  
  x1=min([x1,x2],max=x2)
  y1=min([x1,x2],max=x2)
  return,[x1,y1,x2,y2]
end

pro draw_bbox,bbox,_extra=extra
  plots,/device,[bbox[0],bbox[2],bbox[2],bbox[0],bbox[0]],[bbox[1],bbox[1],bbox[3],bbox[3],bbox[1]],_extra=extra
end

pro test_bbox_intersect,seed
  erase
  bbox1=random_bbox(seed)
  bbox2=random_bbox(seed)
  draw_bbox,bbox1,color=255
  draw_bbox,bbox2,color=255
  bbox_i=find_bbox_intersect(bbox1,bbox2,is_intersect)
  if is_intersect then draw_bbox,bbox_i,color=254 else xyouts,10,10,'no intersect',/device
end