C++ 雙線性插值縮放圖像

縮放灰階圖

cv::Mat bilinear(cv::Mat src, int row, int col){
    int rows = src.rows, cols = src.cols;
    cv::Mat dst(row, col, src.type());
    for(int i = ; i < row; ++i) {
        //以ptr的方式通路dst的資料
        uchar *p = dst.ptr<uchar>(i);
        //使兩個圖像的幾何中心重合，采樣更合理
        float x = (i+)*rows/row-;
        int fx = (int)x;
        //x為坐标的小數部分
        x -= fx;
        //以整數計算速度更快
        short x1 = (f-x)*;
        short x2 =  - x1;
        for(int j = ; j < col; ++j) {
            //trick
            float y = (j+)*cols/col-;
            int fy = (int)y;
            y -= fy;
            //trick
            short y1 = (f-y)*;
            short y2 =  - y1;
            //結果右移22位抵消2048的平方
            p[j] = (src.at<uchar>(fx,fy)*x1*y1 + src.at<uchar>(fx+,fy)*x2*y1
                +src.at<uchar>(fx,fy+)*x1*y2 + src.at<uchar>(fx+,fy+)*x2*y2) >> ;
        }
    }
    return dst;
}