使用C语言实现从avi视频中提取图片

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <linux/videodev2.h>
#include <string.h>
#include <sys/mman.h>
static int zz=1;
 
int main(void){
	
	struct strf{
		unsigned char id[4];             //块ID，固定为strf
		unsigned int size;               //块大小，等于struct avi_strf_chunk去掉id和size的大小
		unsigned int size1;              //size1含义和值同size一样
		unsigned int width;              //视频主窗口宽度（单位：像素）
		unsigned int height;             //视频主窗口高度（单位：像素）
		unsigned short planes;           //始终为1
		unsigned short bitcount;         //每个像素占的位数，只能是1、4、8、16、24和32中的一个
		unsigned char compression[4];    //视频流编码格式，如JPEG、MJPG等
		unsigned int image_size;         //视频图像大小，等于width * height * bitcount / 8
		unsigned int x_pixels_per_meter; //显示设备的水平分辨率，设为0即可
		unsigned int y_pixels_per_meter; //显示设备的垂直分辨率，设为0即可
		unsigned int num_colors;         //含义不清楚，设为0即可
		unsigned int imp_colors;         //含义不清楚，设为0即可
	}str;
	FILE *f=fopen("/home/wzpc/Videos/tra_mjpg.avi","rb");            //必须是JPEG，MJPG格式的avi
	if(f==NULL){
		puts("file error");
		exit(-1);
	}
	fseek(f,0,SEEK_END);
	int fsize=ftell(f);
	fseek(f,0,SEEK_SET);
	
	int fd=fileno(f);
	char *m=mmap(NULL,fsize,PROT_READ,MAP_SHARED,fd,0);
	
	
	
	for(int t=0;t<fsize;t++){
		if((m[t]=='s')&&(m[t+1]=='t')&&(m[t+2]=='r')&&(m[t+3]=='f')){
			
			memcpy(&str,&m[t],sizeof(str));
			printf("%d\n",str.bitcount);
			printf("%s\n",str.compression);
			printf("%d*%d\n",str.width,str.height);
			
			char r[]={'M','J','P','G'};                 //avi 编码必须是jpeg，mjpg
			char r1[]={'J','P','E','G'};
			int bj=memcmp(str.compression,r,4);
			int bj1=memcmp(str.compression,r1,4);
            if((bj==0)||(bj1==0))
			{
			   zz=0;
			}
		    
		}
	}
	
	if(zz!=0){
		puts("no zc");
		exit(-1);
	}
	
	for(int t=0;t<fsize;t++){
		if((m[t]=='0')&&(m[t+1]=='0')&&(m[t+2]=='d')&&(m[t+3]=='c')){
		    char file[10]={};
			sprintf(file,"%d",t);
			
			chdir("/home/wzpc/Pictures/pic_avi");    //存储图片的目录
			FILE * fo=fopen(file,"w+b");
			if(fo==NULL){
				puts("fo error");
				exit(-1);
			}
			
			int k;
			memcpy(&k,&m[t+4],4);
			fwrite(&m[t+8],k,1,fo);                //直接从mmap中读数据到文件
			fclose(fo);
		
		}
  }
	
	munmap(m,fsize);
	return 0;
}

#include<opencv2\opencv.hpp>
#include <iostream>
#include <stdio.h>
#include<fstream>
using namespace std;
using namespace cv;
int main()
{
    //打开视频文件：其实就是建立一个VideoCapture结构
    VideoCapture capture("D:/MyData/zhaohz4/Desktop/Nansha_video/2.mp4");
    //检测是否正常打开:成功打开时，isOpened返回ture
    if (!capture.isOpened())
        cout << "fail toopen!" << endl;
    //获取整个帧数
    long totalFrameNumber = capture.get(CV_CAP_PROP_FRAME_COUNT);
    cout << "整个视频共" << totalFrameNumber << "帧" << endl;
    //设置开始帧()
    long frameToStart = 1;
    capture.set(CV_CAP_PROP_POS_FRAMES, frameToStart);
    cout << "从第" << frameToStart << "帧开始读" << endl;
    //设置结束帧
    int frameToStop = 4000;
    if (frameToStop < frameToStart)
    {
        cout << "结束帧小于开始帧，程序错误，即将退出！" << endl;
        return -1;
    }
    else
    {
        cout << "结束帧为：第" << frameToStop << "帧" << endl;
    }
    //获取帧率
    double rate = capture.get(CV_CAP_PROP_FPS);
    cout << "帧率为:" << rate << endl;
    //定义一个用来控制读取视频循环结束的变量
    bool stop = false;
    //承载每一帧的图像
    Mat frame;
    //显示每一帧的窗口
    namedWindow("Extractedframe");
    //两帧间的间隔时间:
    //int delay = 1000/rate;
    double delay = 2000 / rate;     //??
    //利用while循环读取帧
    //currentFrame是在循环体中控制读取到指定的帧后循环结束的变量
    long currentFrame = frameToStart;
    //滤波器的核
    int kernel_size = 3;
    Mat kernel = Mat::ones(kernel_size, kernel_size, CV_32F) / (float)(kernel_size*kernel_size);
    while (!stop)
    {
        //读取下一帧
        if (!capture.read(frame))
        {
            cout << "读取视频失败" << endl;
            return -1;
        }
        if (currentFrame % 3 == 0)    //每三帧保存一帧
        {
            cout << "正在读取第" << currentFrame << "帧" << endl;
            imshow("Extractedframe", frame);
            cout << "正在写第" << currentFrame << "帧" << endl;
            stringstream str;
            str << "2-"<<currentFrame << ".jpg";     //保存格式
            cout << str.str() << endl;
            imwrite(str.str(), frame);
        }
        //waitKey(intdelay=0)当delay≤ 0时会永远等待；当delay>0时会等待delay毫秒
        //当时间结束前没有按键按下时，返回值为-1；否则返回按键
        //int c = waitKey(delay);
        int c = waitKey(1000);
        //按下ESC或者到达指定的结束帧后退出读取视频
        if ((char)c == 27 || currentFrame > frameToStop)
        {
            stop = true;
        }
        //按下按键后会停留在当前帧，等待下一次按键
        if (c >= 0)
        {
            waitKey(0);
        }
        currentFrame++;
    }
    //关闭视频文件
    capture.release();
    waitKey(0);
    return 0;
}