用opencv 进行hough 变换，怎样得到并输出直线的角度？

程序如下：
#include "cv.h"
#include "highgui.h"
#include <math.h>

int main(int argc, char** argv)
{
    IplImage* src;
    //if( argc == 2 && (src=cvLoadImage(argv[1], 0))!= 0)
if(src=cvLoadImage(argc > 1? argv[1] : "c:\\TestImages\\pic1.png", 0))
    {
        IplImage* dst = cvCreateImage( cvGetSize(src), 8, 1 );
        IplImage* color_dst = cvCreateImage( cvGetSize(src), 8, 3 );
        CvMemStorage* storage = cvCreateMemStorage(0);
        CvSeq* lines = 0;
        int i;
        cvCanny( src, dst, 50, 200, 3 );
        cvCvtColor( dst, color_dst, CV_GRAY2BGR );
#if 1
        lines = cvHoughLines2( dst, storage, CV_HOUGH_STANDARD, 1, CV_PI/180, 150, 0, 0 );

        for( i = 0; i < lines->total; i++ )
        {
            float* line = (float*)cvGetSeqElem(lines, i);
            float rho = line[0];
            float theta = line[1];
            CvPoint pt1, pt2;
            double a = cos(theta), b = sin(theta);
            if( fabs(b) < 0.001 )
            {
                pt1.x = pt2.x = cvRound(rho);
                pt1.y = 0;
                pt2.y = color_dst->height;
            }
            else if( fabs(a) < 0.001 )
            {
                pt1.y = pt2.y = cvRound(rho);
                pt1.x = 0;
                pt2.x = color_dst->width;
            }
            else
            {
                pt1.x = 0;
                pt1.y = cvRound(rho/b);
                pt2.x = cvRound(rho/a);
                pt2.y = 0;
            }
            cvLine( color_dst, pt1, pt2, CV_RGB(255,0,0), 1, 8 );
        }
    
#endif
        cvNamedWindow( "Source", 1 );
        cvShowImage( "Source", src );

        cvNamedWindow( "Hough", 1 );
        cvShowImage( "Hough", color_dst );
 
        cvWaitKey(0);
    }    
}
我想要得到角度。之后根据这个角度对图像进行旋转

你的图是怎样的？
cvHoughLines2能得到多个直线段，你要的到哪个角度啊？