【opencv基础】获取视频帧保存视频或图像帧

前言

对已有的视频进行解帧，得到视频图像帧，便于之后的图像处理。

c++/opencv代码如下：

#include<highgui.h>
#include<cv.h>
#include<iostream>
using namespace std;
using namespace cv;

int main()
{

    CvCapture* capture = cvCaptureFromFile(".\\input_path\\input_video.mp4");
    int fps = (int)cvGetCaptureProperty(capture, CV_CAP_PROP_FPS);
    long nFrame = (long)cvGetCaptureProperty(capture, CV_CAP_PROP_FRAME_COUNT); // 获取总帧数
    int width = (int)cvGetCaptureProperty(capture,CV_CAP_PROP_FRAME_WIDTH);
    int height = (int)cvGetCaptureProperty(capture, CV_CAP_PROP_FRAME_HEIGHT);
    IplImage* image = NULL;
    char save_path[100];
    int i = 0;
    int start = 1;
    int end = 1000;
    if (capture)
    {
        while (1)
        {
            image = cvQueryFrame(capture);
            if (image)
            {
                i++;
                cout << "i=" << i << endl;
                if (i >= start && i <= end)
                {
                    //cout << "save " << i << " th image..." << endl;
                    sprintf(save_path, ".\\output_path\\frames\\%d.jpg", i);
                    cvSaveImage(save_path, image);
                }
                if (i > end)
                {
                    return 0;
                }
            }
        }
    }
}

View Code

注意：

c++代码中的路径必须是反双斜杠！！！

从camera获取视频并保存

/*
Copyright(C) 2019 ABC. ALL rights reserved.
File : save_video.cpp
Brief: save video every 10 minutes.
Coder: happy
Email: xxx.zzzz@abc.com
Date : 20191224
ChLog:
*/
#include "opencv2/opencv.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/core.hpp"
#include <iostream>
#include <string>
#include <time.h>
#include <stdio.h>
const int video_len = 18000;
std::string time_now()
{
    time_t t = time(0);
    char tmp[64];
    strftime(tmp, sizeof(tmp), "%Y%m%dT%H%M%S", localtime(&t));
    return tmp;
}
int main()
{
    // std::string output_dir = "./dms_video/";
    std::string output_dir = "../output/";
    int camera_id = 0;
    cv::VideoCapture cap(camera_id);
    if(!cap.isOpened())
    {
        std::cerr << "ERROR! Unable to open camera.\n";
        return -1;
    }
    int fps = (int)cap.get(CV_CAP_PROP_FPS);
    int width = (int)cap.get(CV_CAP_PROP_FRAME_WIDTH);
    int height = (int)cap.get(CV_CAP_PROP_FRAME_HEIGHT);
    cv::Size frame_size(width, height);
    // cv::Size frame_size(640, 480);
    std::cout << "fps: " << fps << "width: " << width << "height: " << height << std::endl;
    // double begin = 0.0;
    // double end = 0.0;
    // double cost_time = 0.0;
    while(true)
    {
        cv::Mat frame;
        int cnt = video_len;
        cv::VideoWriter writer;
        std::string video_name = output_dir + "TFL_" + time_now() + ".avi";
        std::cout << "video_name: " << video_name << std::endl;
        writer.open(video_name, CV_FOURCC('D', 'I', 'V', '3'), fps, frame_size);
        while(cnt--)
        {
            // begin = (double)cv::getTickCount();
            cap >> frame;
            // end = (double)cv::getTickCount();
            // cost_time = (end-begin)*1000 / cv::getTickFrequency();
            // printf("capture one frame cost time: %fms...\n", cost_time);
            if(frame.empty())
            {
                std::cerr << "ERROR! Blank frame grabbed.\n";
                break;
            }
            // cv::resize(frame, frame, cv::Size(640, 480), 0, 0, CV_INTER_LINEAR);
            cv::imshow("frame", frame);
            // begin = (double)cv::getTickCount();
            writer << frame;
            // end = (double)cv::getTickCount();
            // cost_time = (end-begin)*1000 / cv::getTickFrequency();
            // printf("write one frame cost time: %f ms...\n", cost_time);
            if(char(cv::waitKey(1)) == 'q')
            {
                writer.release();
                frame.release();
                return 0;
            }
        }
        writer.release();
        frame.release();
        if(char(cv::waitKey(1)) == 'q') return 0;
    }
    if(char(cv::waitKey(1)) == 'q') return 0;
    return 0;
}

View Code

从camera获取图像并通过手动保存图像

*
Copyright(C) 2019 ABC. ALL rights reserved.
File : get_frame.cpp
Brief: save frame when click 's'.
Coder: happy
Email: xxx.zzz@abc.com
Date : 20191224
ChLog:
*/
#include "opencv2/opencv.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/core.hpp"
#include <iostream>
#include <string>
#include <time.h>
#include <stdio.h>
// const int video_len = 180;
std::string time_now()
{
    time_t t = time(0);
    char tmp[64] = {0};
    strftime(tmp, sizeof(tmp), "%Y%m%dT%H%M%S", localtime(&t));
    return tmp;
}

int main()
{
    std::string output_dir = "../output/";
    int camera_id = 0;
    cv::VideoCapture cap(camera_id);
    if(!cap.isOpened())
    {
        std::cerr << "ERROR! Unable to open camera.\n";
        return -1;
    }
    int fps = (int)cap.get(CV_CAP_PROP_FPS);
    int width = (int)cap.get(CV_CAP_PROP_FRAME_WIDTH);
    int height = (int)cap.get(CV_CAP_PROP_FRAME_HEIGHT);
    cv::Size frame_size(width, height);
    // cv::Size frame_size(640, 480);
    std::cout << "fps: " << fps << "width: " << width << "height: " << height << std::endl;
    int cnt = 0;
    cv::Mat frame;
    char strnum[64] = {0};
    while(true)
    {
        cap >> frame;
        if(frame.empty())
        {
            std::cerr << "ERROR! Blank frame grabbed.\n";
            break;
        }
        cv::imshow("frame", frame);
        
        if(char(cv::waitKey(1)) == 's')
        {
            sprintf(strnum, "%05d_", cnt++);
            std::string imgname = output_dir + "TFL_" + strnum + time_now() + ".png";
            cv::imwrite(imgname, frame);
        }
        else if(char(cv::waitKey(1)) == 'q')
        {
            frame.release();
            cap.release();
            return 0;
        }
    }
    cap.release();
    return 0;
}

View Code

CMakeLists.txt

cmake_minimum_required(VERSION 2.8)
set(CMAKE_CXX_COMPILER "g++")
set(CMAKE_CXX_FLAGS "-std=c++11 -O3 -DNDEBUG -fopenmp -ffast-math -Wall")
project(get_video)
# set_property(GLOBAL PROPERTY USE_FOLDERS ON)
include_directories(include)
aux_source_directory(src DIR_SRCS)
find_package(OpenCV 3.3.1 REQUIRED)
include_directories(${OpenCV_INCLUDE_DIRS})
add_executable(${PROJECT_NAME} ${DIR_SRCS})
target_link_libraries(${PROJECT_NAME} ${OpenCV_LIBS})
# # build shared lib.
# set(LIBRARY_OUTPUT_PATH ${CMAKE_SOURCE_DIR}/lib)
# list(APPEND CURRENT_INCLUDE ${OpenCV_INCLUDE_DIRS} include)
# add_library(${PROJECT_NAME} SHARED ${DIR_SRCS} ${CURRENT_INCLUDE})
message("project_name: ${PROJECT_NAME}")
message("DIR_SRCS: ${DIR_SRCS}")
message("OpenCV_INCLUDE_DIRS: ${OpenCV_INCLUDE_DIRS}")
message("OpenCV_LIBS: ${OpenCV_LIBS}")