Question

新手问题，是的，我花了很多时间筛选类似的问题和答案，没有运气。

我要做的是按顺序保存视频文件中的帧。我已经设法使用c保存一个图像，之后我似乎无法保存图像。我已经开始在opencv而不是c中使用c ++，我所能做的只是观看视频而不是从中保存任何jpg。

如果有帮助，我在mac上使用opencv2.4.4a。下面是我的例子

#include <stdio.h>
#include <stdlib.h>
#include <opencv/cv.h>
#include <opencv/highgui.h>
#include <iostream>

using namespace cv;
using namespace std;

int main (int argc, char** argv)
{
//initializing capture from file
CvCapture * capture = cvCaptureFromAVI ("/example/example.mov");

//Capturing a frame
IplImage* img = 0;
if(!cvGrabFrame(capture))      //capture a frame
{
printf)Could not grab a fram\n\7");
exit(0);
}
img=cvRerieveFrame(capture);    //retrieve the captured frame

//writing an image to a file
if (!cvSaveImage("/frames/test.jpg", img))
printf("Could not save: %s\n","test.jpg");

//free resources
cvReleaseCapture(&capture);

}

提前谢谢

编辑上面的内容。

我已添加到上面的代码中，导致使用test.jpg保存图像，然后用下一帧重写。如何告诉opencv不复制最后一个图像并将下一帧重命名为test_2.jpg，例如test_1.jpg，test_2.jpg等等？

double num_frames = cvGetCaptureProperty (capture, CV_CAP_PROP_FRAME_COUNT);

for (int i = 0; i < (int)num_frames; i++)
{
img = cvQueryFrame(capture);
cvSaveImage("frames/test.jpg", img);
}

cvReleaseCapture(&capture);
}

Answer 1

这是我的代码......我尝试了很多，最后成功了这是使用opencv 3的c ++ ...希望它有效

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


using namespace cv;
using namespace std;

 Mat frame,img;
    int counter;

int main(int,char**)
   {
        VideoCapture vid("video3.avi");


while (!vid.isOpened())
{
    VideoCapture vid("video2.MOV");
    cout << "charging" << endl;
    waitKey(1000);

}

cout << "Video opened!" << endl;

while(1)
{
    stringstream file;

    vid.read(frame);
    if(frame.empty()) break;
    file << "/home/pedro/workspace/videoFrame/Debug/frames/image" << counter << ".jpg";
    counter++;
    imwrite(file.str(),frame);

    char key = waitKey(10);
 if ( key == 27)
 {break;}


}


}

Answer 2

使用一个索引来跟踪文件名中的数字部分。在图像捕获循环中，使用文件名添加索引并构建最终文件名。

这是一个例子：

while(1)
{
     cap.read ( frame);
     if( frame.empty()) break;
     imshow("video", frame);
     char filename[80];
     sprintf(filename,"C:/Users/cssc/Desktop/testFolder/test_%d.png",i);
     imwrite(filename, frame);
     i++;
     char key = waitKey(10);
     if ( key == 27) break;
}

Answer 3

这是我在Python3.0中执行的方法。必须具有CV2 3+版本才能运行。此功能以给定的频率保存图像。

import cv2
import os
print(cv2.__version__)

# Function to extract frames 
def FrameCapture(path,frame_freq): 

    # Path to video file 
    video = cv2.VideoCapture(path) 
    success, image = video.read()

    # Number of frames in video
    fps = int(video.get(cv2.CAP_PROP_FPS))
    length = int(video.get(cv2.CAP_PROP_FRAME_COUNT))

    print('FPS:', fps)
    print('Extracting every {} frames'.format(frame_freq))
    print('Total Frames:', length)
    print('Number of Frames Saved:', (length // frame_freq) + 1)

    # Directory for saved frames
    try:
        frame_dir = path.split('.')[0]
        os.mkdir(frame_dir)
    except FileExistsError:
        print('Directory ({}) already exists'.format(frame_dir))

    # Used as counter variable 
    count = 0

    # checks whether frames were extracted 
    success = 1

    # vidObj object calls read 
    # function extract frames 

    while count < length :
        video.set(cv2.CAP_PROP_POS_FRAMES , count)
        success, image = video.read()
        # Saves the frames with frame-count 
        cv2.imwrite(frame_dir + "/frame%d.jpg" % count, image)
        count = count + frame_freq

使用opencv2从视频保存图像序列

3 个答案: