目录
读写图像
imread 可以指定加载为灰度或者RGB图像
Imwrite 保存图像文件,类型由扩展名决定
读写像素
读一个GRAY像素点的像素值
(CV_8UC1) Scalar intensity = img.at<uchar>(y, x);
或者 Scalar intensity = img.at<uchar>(Point(x, y));
读一个RGB像素点的像素值
Vec3f intensity = img.at<Vec3f>(y, x);
float blue = intensity.val[0];
float green = intensity.val[1];
float red = intensity.val[2];
修改像素值
灰度图像
img.at<uchar>(y, x) = 128;
RGB三通道图像
img.at<Vec3b>(y,x)[0]=128; // blue
img.at<Vec3b>(y,x)[1]=128; // green
img.at<Vec3b>(y,x)[2]=128; // red
空白图像赋值
img = Scalar(0);
ROI选择
Rect r(10, 10, 100, 100);
Mat smallImg = img(r);
Vec3b与Vec3F
Vec3b对应三通道的顺序是blue、green、red的uchar类型数据。
Vec3f对应三通道的float类型数据
把CV_8UC1转换到CV32F1实现如下: src.convertTo(dst, CV_32F);
#include <opencv2/opencv.hpp>
#include <iostream>
using namespace std;
using namespace cv;
int main(int argc, char** argv) {
Mat src;
src = imread("D:/vcprojects/images/test.png");
if (src.empty()) {
cout << "could not load image..." << endl;
return -1;
}
namedWindow("input", CV_WINDOW_AUTOSIZE);
imshow("input", src);
/*Mat dst;
dst = Mat(src.size(), src.type());
dst = Scalar(127, 0, 255);
namedWindow("output", CV_WINDOW_AUTOSIZE);
imshow("output", dst);*/
Mat dst;
//src.copyTo(dst);
namedWindow("output", CV_WINDOW_AUTOSIZE);
cvtColor(src, dst, CV_BGR2GRAY);
printf("input image channels : %d\n", src.channels());
printf("output image channels : %d\n", dst.channels());
int cols = dst.cols;
int rows = dst.rows;
printf("rows : %d cols : %d\n", rows, cols);
const uchar* firstRow = dst.ptr<uchar>(0);
printf("fist pixel value : %d\n", *firstRow);
Mat M(100, 100, CV_8UC1, Scalar(127));
//cout << "M =" << endl << M << endl;
Mat m1;
m1.create(src.size(), src.type());
m1 = Scalar(0, 0, 255);
Mat csrc;
Mat kernel = (Mat_<char>(3, 3) << 0, -1, 0, -1, 5, -1, 0, -1, 0);
filter2D(src, csrc, -1, kernel);
Mat m2 = Mat::eye(2, 2, CV_8UC1);
cout << "m2 =" << endl << m2 << endl;
imshow("output", m2);
waitKey(0);
return 0;
}