说明：  利用Hough transform计算图片中两条直线间的角度，同时计算图片中所有直线汇聚于某一点的坐标
(Find the angle of these tow lines shown in the image by Hough transform.As you can see in the image all of such lines are going to merge to a special point (perspective or vanishing point). Find the coordinate of this point by using intersection of the two lines you obtain in part (a). (Hint: You can use mfile hcross which follows with the problem-set materials).)