如何用指针访问opencv cv::Mat数据？ptr＜uchar＞()

Posted 2022-02-16 Dontla

示例：

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

using namespace cv;
using namespace std;

int main(int argc, const char* argv[]) 

	Mat src, dst1;

	src = imread("./test.jpg");
	//if (src.empty()) 
	if (!src.data)
		printf("could not load image...\\n");
		return -1;
	
	namedWindow("input img");	//默认自动窗口大小
	imshow("input img", src);

	dst1 = Mat(src.size(), src.type());
	dst1 = Scalar(127, 0, 255);
	namedWindow("output img1");	//默认自动窗口大小
	imshow("output img1", dst1);

	//通过指针访问像素数值
	//(0)表示第0行首像素地址，(1)表示第1行首像素地址，(0,0)表示第0行首像素地址，(0,1)表示第0行1像素地址

	//const uchar* firstRow = dst1.ptr<uchar>(0);	//可以
	//const uchar* firstRow = dst1.ptr<uchar>(0, 0);	//可以
	//const uchar* firstRow = dst1.ptr<uchar>(0, 0, 0);	//不行

	const uchar* firstRow = dst1.ptr<uchar>(0, 0) + 1;
	printf("first pixel %p value:%d\\n", firstRow, *firstRow);	//first pixel 000001FDC64700C1 value:0
	const uchar* secondRow = dst1.ptr<uchar>(0, 0) + 2;
	printf("second pixel %p value:%d\\n", secondRow, *secondRow);	//second pixel 000001FDC64700C2 value:255
	const uchar* thirdRow = dst1.ptr<uchar>(0, 0) + 3;
	printf("third pixel %p value:%d\\n", thirdRow, *thirdRow);	//third pixel 000001FDC64700C3 value:127
	const uchar* forthRow = dst1.ptr<uchar>(0, 0) + 4;
	printf("forth pixel %p value:%d\\n", forthRow, *forthRow);	//forth pixel 000001FDC64700C4 value:0


	waitKey(0);
	return 0;

参考文章1：【opencv4】opencv视频教程 C++（opencv教程）3、矩阵的掩膜操作（filter2D）

参考文章2：访问cv::Mat中的数据时遇到的指针类型问题