九、OpenCV中视频的录制

一、OpenCV 视频录制概述

在 OpenCV 中，视频录制主要靠 cv::VideoWriter 类。它可以把连续的 cv::Mat 帧写入一个视频文件（如 .avi、.mp4 等）。

VideoWriter类
构造函数：

VideoWriter::VideoWriter(const String &filename,int fourcc,double fps,Size frameSize,bool isColor = true);

参数说明：

• filename：保存的视频文件名，例如 “output.avi”
• fourcc：视频编码方式，如 CV_FOURCC(‘M’,‘J’,‘P’,‘G’) 或 VideoWriter::fourcc(‘M’,‘J’,‘P’,‘G’)
• fps：帧率（帧每秒）
• frameSize：视频每帧的尺寸，Size(width, height)
• isColor：是否为彩色视频，true 彩色，false 灰度

常用编码（fourcc）：

int fourcc = VideoWriter::fourcc('M','J','P','G'); // AVI 常用
int fourcc_mp4 = VideoWriter::fourcc('a','v','c','1'); // MP4 H264

二、示例代码

示例 1：从摄像头录制视频

#include <opencv2/opencv.hpp>
#include <iostream>
using namespace cv;
using namespace std;int main() {VideoCapture cap(0); // 打开摄像头if (!cap.isOpened()) {cout << "Cannot open camera" << endl;return -1;}// 视频参数int frame_width = static_cast<int>(cap.get(CAP_PROP_FRAME_WIDTH));int frame_height = static_cast<int>(cap.get(CAP_PROP_FRAME_HEIGHT));VideoWriter writer("output.avi",VideoWriter::fourcc('M','J','P','G'),30, Size(frame_width, frame_height));Mat frame;while (true) {cap >> frame;if (frame.empty()) break;writer.write(frame); // 写入视频imshow("Camera", frame);if (waitKey(1) == 27) break; // 按 ESC 停止}cap.release();writer.release();destroyAllWindows();return 0;
}

示例 2：将视频文件处理后保存

#include <opencv2/opencv.hpp>
#include <iostream>
using namespace cv;
using namespace std;int main() {VideoCapture cap("opencv_demo.mp4");if (!cap.isOpened()) return -1;int width = cap.get(CAP_PROP_FRAME_WIDTH);int height = cap.get(CAP_PROP_FRAME_HEIGHT);VideoWriter writer("output_processed.avi",VideoWriter::fourcc('M', 'J', 'P', 'G'),30, Size(width, height));Mat frame;while (true) {cap >> frame;if (frame.empty()) break;// 处理帧，例如灰度cvtColor(frame, frame, COLOR_BGR2GRAY);cvtColor(frame, frame, COLOR_GRAY2BGR); // 保持三通道以写入writer.write(frame);}cap.release();writer.release();return 0;
}

示例3：自动读取指定文件夹下所有图片生成视频

#include <opencv2/opencv.hpp>
#include <iostream>
#include <filesystem>
#include <vector>
#include <algorithm>
using namespace cv;
using namespace std;
namespace fs = std::filesystem;int main() {string folderPath = "images"; // 图片文件夹路径string outputVideo = "output_video.avi";double fps = 30.0; // 帧率vector<string> imgFiles;// 遍历文件夹，收集图片路径for (const auto& entry : fs::directory_iterator(folderPath)) {if (entry.is_regular_file()) {string ext = entry.path().extension().string();// 支持 jpg/png/bmpif (ext == ".jpg" || ext == ".png" || ext == ".bmp")imgFiles.push_back(entry.path().string());}}if (imgFiles.empty()) {cout << "No images found in folder!" << endl;return -1;}// 按文件名排序sort(imgFiles.begin(), imgFiles.end());// 读取第一张图片获取尺寸Mat firstImg = imread(imgFiles[0]);if (firstImg.empty()) {cout << "Failed to read " << imgFiles[0] << endl;return -1;}Size frameSize(firstImg.cols, firstImg.rows);// 创建 VideoWriterVideoWriter writer(outputVideo,VideoWriter::fourcc('M','J','P','G'),fps,frameSize,true);if (!writer.isOpened()) {cout << "Cannot open VideoWriter!" << endl;return -1;}// 写入每张图片for (const auto& file : imgFiles) {Mat img = imread(file);if (img.empty()) {cout << "Failed to read " << file << endl;continue;}// 尺寸不一致就 resizeif (img.size() != frameSize) {resize(img, img, frameSize);}writer.write(img);}writer.release();cout << "Video saved as " << outputVideo << endl;return 0;
}