一、读取图像

//图片路径QString appPath = QCoreApplication::applicationDirPath();QString imagePath = appPath + "/sun.png";//读取图像cv::Mat img = cv::imread(imagePath.toStdString()); //IMREAD_GRAYSCALE 灰度图 IMREAD_UNCHANGED 具有透明通道if (img.empty()) {qDebug()<< "Could not load image!\n";return;}//创建窗口cv::namedWindow("input", cv::WINDOW_AUTOSIZE);//显示图像cv::imshow("input", img);//参数为0一直阻塞cv::waitKey(0);//销毁窗口cv::destroyAllWindows();

二、保存图像

//保存为png透明通道vector<int>opts;opts.push_back(IMWRITE_PAM_FORMAT_RGB_ALPHA);imwrite("D:/img_bgra.png", img, opts);//保存为单通道灰度图像img = cv::imread(imagePath.toStdString(), IMREAD_GRAYSCALE);vector<int> opts_gray;opts_gray.push_back(IMWRITE_PAM_FORMAT_GRAYSCALE);imwrite("D:/img_gray.png", img, opts_gray);//保存为默认的彩色BGR图像imwrite("D:/img_BGR.png", img);//保存为png彩色压缩图像img = imread(imagePath.toStdString(), IMREAD_ANYCOLOR);vector<int> opts_png_anycolor;opts_png_anycolor.push_back(IMWRITE_PAM_FORMAT_GRAYSCALE);opts_png_anycolor.push_back(9);imwrite("D:/img_png_anycolor.png", img, opts_png_anycolor);//保存为JPG高压缩比图像img = imread(imagePath.toStdString(), IMREAD_COLOR);vector<int> opts_jpeg;opts_jpeg.push_back(IMWRITE_JPEG_QUALITY);opts_jpeg.push_back(50);opts_jpeg.push_back(IMWRITE_JPEG_OPTIMIZE);opts_jpeg.push_back(1);imwrite("D:/img_jpeg.jpg", img, opts_jpeg);

三、加载视频

	//视频路径QString appPath = QCoreApplication::applicationDirPath();QString videoPath = appPath + "/vtest.avi";cv::VideoCapture capture;capture.open(videoPath.toStdString(),CAP_FFMPEG);//从摄像头读取//capture.open(0, CAP_DSHOW);cv::Mat frame;while (true) {//读帧bool ret = capture.read(frame);if (!ret)break;imshow("frame", frame);//添加帧处理 等待 100 毫秒，检查用户是否按下键盘上的按键char c = waitKey(100);//按下的是 ESC 键 (ASCII 值为 27)，则跳出循环，停止播放视频if (c == 27)break;}waitKey(0);destroyAllWindows();

四、获取视频属性

	//视频路径QString appPath = QCoreApplication::applicationDirPath();QString videoPath = appPath + "/vtest.avi";cv::VideoCapture capture;capture.open(videoPath.toStdString(),CAP_FFMPEG);qDebug() << u8"高：" << capture.get(CAP_PROP_FRAME_HEIGHT);qDebug() << u8"宽：" << capture.get(CAP_PROP_FRAME_WIDTH);qDebug() << u8"帧率FPS：" << QString::number(capture.get(CAP_PROP_FPS));qDebug() << u8"总帧率：" << capture.get(CAP_PROP_FRAME_COUNT);

五、保存视频

	//视频路径QString appPath = QCoreApplication::applicationDirPath();QString videoPath = appPath + "/vtest.avi";cv::VideoCapture capture;capture.open(videoPath.toStdString(), CAP_FFMPEG);qDebug() << u8"高：" << capture.get(CAP_PROP_FRAME_HEIGHT);qDebug() << u8"宽：" << capture.get(CAP_PROP_FRAME_WIDTH);qDebug() << u8"帧率FPS：" << capture.get(CAP_PROP_FPS);qDebug() << u8"总帧率：" << capture.get(CAP_PROP_FRAME_COUNT);//保存视频路径QString savevideoPath = appPath + "/output.avi";cv::VideoWriter writer(savevideoPath.toStdString(), capture.get(CAP_PROP_FOURCC), capture.get(CAP_PROP_FPS), Size(capture.get(CAP_PROP_FRAME_WIDTH), capture.get(CAP_PROP_FRAME_HEIGHT)));cv::Mat frame;while (true) {//读帧bool ret = capture.read(frame);if (!ret)break;imshow("frame", frame);//添加帧处理 writer.write(frame);//等待 100 毫秒，检查用户是否按下键盘上的按键char c = waitKey(100);//按下的是 ESC 键 (ASCII 值为 27)，则跳出循环，停止播放视频if (c == 27)break;}capture.release();writer.release();waitKey(0);destroyAllWindows();

六、Mat遍历

1. 数组下标

for (int row = 0; row < h; row++){for (int col = 0; col < w; col++){if (dim == 1)//灰度图像{int pv = image.at<uchar>(row,col);//像素是字节类型image.at<uchar>(row, col) = 255 - pv;}if (dim == 3)//彩色图像{Vec3b bgr = image.at<Vec3b>(row, col);image.at<Vec3b>(row, col)[0] = 255 - bgr[0];image.at<Vec3b>(row, col)[1] = 255 - bgr[1];image.at<Vec3b>(row, col)[2] = 255 - bgr[2];}}}

2. 指针

for (int row = 0; row < h; row++)
{uchar* current_row = image.ptr<uchar>(row);for (int col = 0; col < w; col++){if (dim == 1)//灰度图像{int pv = *current_row;*current_row++ = 255 - *current_row;}if (dim == 3)//彩色图像{*current_row++ = 255 - *current_row;*current_row++ = 255 - *current_row;*current_row++ = 255 - *current_row;}}
}

七、Mat加减乘除

#include <opencv2/opencv.hpp>using namespace cv;int main() {Mat image = imread("image.jpg");if (image.empty()) {std::cout << "无法加载图像" << std::endl;return -1;}// 加法变换Mat addResult;add(image, Scalar(50, 50, 50), addResult); // 将像素值增加50// 减法变换Mat subtractResult;subtract(image, Scalar(50, 50, 50), subtractResult); // 将像素值减去50// 乘法变换Mat multiplyResult;multiply(image, Scalar(0.5, 0.5, 0.5), multiplyResult); // 将像素值乘以0.5// 除法变换Mat divideResult;divide(image, Scalar(2.0, 2.0, 2.0), divideResult); // 将像素值除以2.0imshow("Original Image", image);imshow("Addition Result", addResult);imshow("Subtraction Result", subtractResult);imshow("Multiplication Result", multiplyResult);imshow("Division Result", divideResult);waitKey(0);return 0;
}

七、亮度调节demo

Mat src, dst, m;
int lightness = 50;static void on_track(int, v