【OpenCV】-22、像素重映射(cv::remap)

【OpenCV】像素重映射(cv::remap)

什么是像素重映射

简单点说，就是把输入图像中各个像素，按照一定的规则映射到另外一张图像的对应位置上去，形成一张新的图像。

相关APIcv::remap

Remap(
InputArray src,// 输入图像
OutputArray dst,// 输出图像
InputArray  map1,// x 映射表 CV_32FC1/CV_32FC2
InputArray map2,// y 映射表
int interpolation,// 选择的插值方法，常见线性插值，可选择立方等
int borderMode,// BORDER_CONSTANT
const Scalar borderValue// color 
)

代码实现

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

using namespace cv;
using namespace std;

Mat src, dst;
Mat map_x, map_y;
int index = 0;
void update_map(void);

int main(int argc, char** argv)
{
	src = imread("1.jpg");
	if (src.empty()) {
		cout << "cannot load the image..." << endl;
		return -1;
	}
	char input_title[] = "input";
	char output_title[] = "remap_img";
	namedWindow(input_title, CV_WINDOW_AUTOSIZE);
	imshow(input_title, 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();
		remap(src, dst, map_x, map_y, INTER_LINEAR, 0, 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://缩小
				if (col > (src.cols*0.25) && (col < src.rows*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://X方向对调
				map_x.at<float>(row, col) = float(src.cols - col-1);
				map_y.at<float>(row, col) = row;
				break;
			case 2://Y方向对调
				map_x.at<float>(row, col) = col;
				map_y.at<float>(row, col) = float(src.rows - row-1);
				break;
			case 3://XY对调
				map_x.at<float>(row, col) = float(src.cols - col - 1); 
				map_y.at<float>(row, col) = float(src.rows - row - 1);
				break;
			}
		}
	}

}

实验效果
原图

缩小

X方向对调

Y方向对调

XY方向皆对调