什麼是畫素重對映

簡單點說就是把輸入影象中各個畫素按照一定的規則對映到另外一張影象的對應位置上去，形成一張新的影象。

API：

Remap(
InputArray src,// 輸入影象
OutputArray dst,// 輸出影象
InputArray  map1,// x 對映表 CV_32FC1/CV_32FC2
InputArray map2,// y 對映表
int interpolation,// 選擇的插值方法，常見線性插值，可選擇立方等
int borderMode,// BORDER_CONSTANT
const Scalar borderValue// color 

)

程式碼：

#include <iostream>
#include <opencv2/opencv.hpp>
using namespace std;
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()
{
    src = imread("D:/opencvSRC/test.jpg");
    if (!src.data) {
        printf("could 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);
        printf("c == %d\n", c);
        if ((char)c == 27) {
            break;
        }
        index = c % 4;
        update_map();
        remap(src, dst, map_x, map_y, INTER_LINEAR, BORDER_CONSTANT, Scalar(0, 255, 255));
        imshow(OUTPUT_TITLE, dst);
    }

    waitKey(0);

    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:
                if (col > (src.cols * 0.25) && col <= (src.cols*0.75) && row > (src.rows*0.25) && row <= (src.rows*0.75)) {
                    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:
                map_x.at<float>(row, col) = (src.cols - col - 1);
                map_y.at<float>(row, col) = row;
                break;
            case 2:
                map_x.at<float>(row, col) = col;
                map_y.at<float>(row, col) = (src.rows - row - 1);
                break;
            case 3:
                map_x.at<float>(row, col) = (src.cols - col - 1);
                map_y.at<float>(row, col) = (src.rows - row - 1);
                break;
            }

        }
    }
}
 

效果：