像素跳变

bool w2b = ((left - right) > diff && (((top - down) > diff && (lefttop - rightdown) > diff)|| (down-top>diff && leftdown -righttop>diff)));
bool b2w = ((right - left) > diff && (((top - down) > diff && (righttop - leftdown) > diff) || (down - top>diff && rightdown - lefttop>diff)));

if (w2b)//white->black
   {
    CvPoint start = CvPoint(j, i);
    cvCircle(&im, start, 1, CvScalar(255, 0, 0),8, 8);
    if (j - pre > 2)
    {
     printf("%d ", j - pre);
     pre = j;
    }
   }