车牌定位实现

class CPlateLocate 
{
public:
    CPlateLocate();

    //! 车牌定位
    int plateLocate(Mat, vector<Mat>& );

    //! 车牌的尺寸验证
    bool verifySizes(RotatedRect mr);

    //! 结果车牌显示
    Mat showResultMat(Mat src, Size rect_size, Point2f center);

    //! 设置与读取变量
    //...

protected:
    //! 高斯模糊所用变量
    int m_GaussianBlurSize;

    //! 连接操作所用变量
    int m_MorphSizeWidth;
    int m_MorphSizeHeight;

    //! verifySize所用变量
    float m_error;
    float m_aspect;
    int m_verifyMin;
    int m_verifyMax;

    //! 角度判断所用变量
    int m_angle;

    //! 是否开启调试模式，0关闭，非0开启
    int m_debug;
};

    Mat grad_x, grad_y;
    Mat abs_grad_x, abs_grad_y;
    Mat dst;
    Sobel( out, grad_x, CV_16S, 1, 0, 3, 1, 0, BORDER_DEFAULT );
    convertScaleAbs( grad_x, abs_grad_x );
    Sobel( out, grad_y, CV_16S, 0, 1, 3, 1, 0, BORDER_DEFAULT );
    convertScaleAbs( grad_y, abs_grad_y );
    addWeighted( abs_grad_x, 1, abs_grad_y, 0, 0, dst);

Mat element = getStructuringElement(MORPH_RECT, Size(getM_MorphSizeWidth(), getM_MorphSizeHeight()) );
morphologyEx(img_threshold, img_threshold, MORPH_CLOSE, element);

 vector< vector< Point> > contours;
    findContours(img_threshold, contours, // a vector of contours
            CV_RETR_EXTERNAL, // 提取外部轮廓
            CV_CHAIN_APPROX_NONE); // all pixels of each contours
    Mat result;
    src.copyTo(result);
    drawContours(result, contours,
                 -1, // draw all contours
                 Scalar(0,0,255), // in blue
                 1); // with a thickness of 

bool CPlateLocate::verifySizes(RotatedRect mr) {
    float error = m_error;
    //Spain car plate size: 52x11 aspect 4,7272
    //China car plate size: 440mm*140mm，aspect 3.142857
    float aspect = m_aspect;
    //Set a min and max area. All other patchs are discarded
    //int min= 1*aspect*1; // minimum area
    //int max= 2000*aspect*2000; // maximum area
    int min= 44*14*m_verifyMin; // minimum area
    int max= 44*14*m_verifyMax; // maximum area
    //Get only patchs that match to a respect ratio.
    float rmin= aspect-aspect*error;
    float rmax= aspect+aspect*error;

    int area= mr.size.height * mr.size.width;
    float r = (float)mr.size.width / (float)mr.size.height;
    if(r < 1)
    {
        r= (float)mr.size.height / (float)mr.size.width;
    }

    if(( area < min || area > max ) || ( r < rmin || r > rmax ))
    {
        return false;
    }
    else
    {
        return true;
    }
}

int k = 1;
    for(int i=0; i< rects.size(); i++)
    {
        RotatedRect minRect = rects[i];
        if(verifySizes(minRect))
        {    
            // rotated rectangle drawing 
            // Get rotation matrix
            // 旋转这部分代码确实可以将某些倾斜的车牌调整正，
            // 但是它也会误将更多正的车牌搞成倾斜！所以综合考虑，还是不使用这段代码。
            // 2014-08-14,由于新到的一批图片中发现有很多车牌是倾斜的，因此决定再次尝试
            // 这段代码。
            if(m_debug)
            { 
                Point2f rect_points[4]; 
                minRect.points( rect_points );
                for( int j = 0; j < 4; j++ )
                    line( result, rect_points[j], rect_points[(j+1)%4], Scalar(0,255,255), 1, 8 );
            }

            float r = (float)minRect.size.width / (float)minRect.size.height;
            float angle = minRect.angle;
            Size rect_size = minRect.size;
            if (r < 1)
            {
                angle = 90 + angle;
                swap(rect_size.width, rect_size.height);
            }
            //如果抓取的方块旋转超过m_angle角度，则不是车牌，放弃处理
            if (angle - m_angle < 0 && angle + m_angle > 0)
            {
                //Create and rotate image
                Mat rotmat = getRotationMatrix2D(minRect.center, angle, 1);
                Mat img_rotated;
                warpAffine(src, img_rotated, rotmat, src.size(), CV_INTER_CUBIC);

                Mat resultMat;
                resultMat = showResultMat(img_rotated, rect_size, minRect.center, k++);

                resultVec.push_back(resultMat);
            }
        }

 Mat rotmat = getRotationMatrix2D(minRect.center, angle, 1);
 Mat img_rotated;
 warpAffine(src, img_rotated, rotmat, src.size(), CV_INTER_CUBIC);

//! 显示最终生成的车牌图像，便于判断是否成功进行了旋转。
Mat CPlateLocate::showResultMat(Mat src, Size rect_size, Point2f center, int index)
{
    Mat img_crop;
    getRectSubPix(src, rect_size, center, img_crop);

    if(m_debug)
    { 
        stringstream ss(stringstream::in | stringstream::out);
        ss << "tmp/debug_crop_" << index << ".jpg";
        imwrite(ss.str(), img_crop);
    }

    Mat resultResized;
    resultResized.create(HEIGHT, WIDTH, TYPE);

    resize(img_crop, resultResized, resultResized.size(), 0, 0, INTER_CUBIC);

    if(m_debug)
    { 
        stringstream ss(stringstream::in | stringstream::out);
        ss << "tmp/debug_resize_" << index << ".jpg";
        imwrite(ss.str(), resultResized);
    }

    return resultResized;
}