图像映射

#include <opencv2/opencv.hpp>
#include <iostream>
#include <math.h>

using namespace cv;
Mat src, dst, map_x, map_y;
const char* OUTPUT_TITLE = "remap demo";
int index = 0;
void update_map(void);
int main(int argc, char** argv) {
    src = imread(".//pic//kate.png");
    if (!src.data) {
        printf("can not load image...\n");
        return -1;
    }
    char input_win[] = "input image";
    namedWindow(input_win, CV_WINDOW_AUTOSIZE);
    namedWindow(OUTPUT_TITLE, CV_WINDOW_AUTOSIZE);
    imshow(input_win, src);

    map_x.create(src.size(), CV_32FC1);
    map_y.create(src.size(), CV_32FC1);

    int c = 0;
    while (true) {
        c = waitKey(500);
        if ((char)c == 27) {
            break;
        }
        index = c % 4;
        update_map();
        //map_x,是x的映射关系
        //map_y,是y的映射关系
        remap(src, dst, map_x, map_y, INTER_LINEAR, BORDER_CONSTANT, Scalar(0, 255, 255));
        imshow(OUTPUT_TITLE, dst);
    }

    return 0;
}

void update_map(void) {
    for (int row = 0; row < src.rows; row++) {
        for (int col = 0; col < src.cols; col++) {
            switch (index) {
            case 0:
                //图像缩放到四分之一处
                if (col > (src.cols * 0.25) && col <= (src.cols * 0.75) && row > (src.rows * 0.25) && row <= (src.rows * 0.75))
                {
                    //src.cols * 0.25相当于减去左边的长度,乘以二是以2进行采样
                    map_x.at<float>(row, col) = 2 * (col - (src.cols * 0.25));
                    map_y.at<float>(row, col) = 2 * (row - (src.rows * 0.25));
                }
                else 
                {
                    map_x.at<float>(row, col) = 0;
                    map_y.at<float>(row, col) = 0;
                }
                break;
            case 1:
                //左右互换
                map_x.at<float>(row, col) = (src.cols - col - 1);
                map_y.at<float>(row, col) = row;
                break;
            case 2:
                //上下互换
                map_x.at<float>(row, col) = col;
                map_y.at<float>(row, col) = (src.rows - row - 1);
                break;
            case 3:
                //左右,上下互换
                map_x.at<float>(row, col) = (src.cols - col - 1);
                map_y.at<float>(row, col) = (src.rows - row - 1);
                break;
            }

        }
    }
}