图片缩放

#include <opencv2/opencv.hpp>
#include <stdio.h>

using namespace cv;

int main(int argc, char const *argv[])
{
    Mat m1 = imread("image.jpg");
    Mat m2(240, 256, CV_8UC3);

    int w1 = m1.cols;
    int h1 = m1.rows;

    int w2 = m2.cols;
    int h2 = m2.rows;

    int x_ratio = (int)((w1 << 16) / w2) + 1;
    int y_ratio = (int)((h1 << 16) / h2) + 1;

    int x2, y2;
    for (int i = 0; i < m2.rows; ++i)
    {
        for (int j = 0; j < m2.cols; j++)
        {
            x2 = ((j * x_ratio) >> 16);
            y2 = ((i * y_ratio) >> 16);

            m2.at<Vec3b>(i, j)[0] = m1.at<Vec3b>(y2, x2)[0]; // BLUE
            m2.at<Vec3b>(i, j)[1] = m1.at<Vec3b>(y2, x2)[1];
            m2.at<Vec3b>(i, j)[2] = m1.at<Vec3b>(y2, x2)[2];
        }
    }

    imshow("原始图", m1);
    imshow("结果", m2);
    waitKey(0);

    return 0;
}