视频分解图片原理；图片合成视频原理

（1）加载视频

（2）读取视频信息

（3）解码视频，拿到单帧信息

帧率：视频每秒钟展示多少张图片；帧率高我们看到的图片才是连续的；帧率低我们看到的图片就相当于非连续的；

宽度；高度

接下来是视频保存成图片；用i计数，保存图片个数；

flag,frame=cap.read()

第一个参数flag的值为True或False，代表有没有读到图片

第二个参数是frame，是当前截取一帧的图片。

filename是图片保存名字；

iwrite保存图片；

（4）展示，保存图片

/************************************************************************
* @ Project Creation time:2018/5/22
* @ Function:从文件中获取视频分解成图片
************************************************************************/
#include<opencv2/opencv.hpp>
#include "iostream"
using namespace cv;
using namespace std;


int main()
{
	Mat frame;
	char outfile[50];
	VideoCapture cap("E:\VS2015Opencv\vs2015\project\video\01.avi");
	if (!cap.isOpened())
	{
		cout << "打开视频失败！" << endl;
		return -1;
	}

	int totalFrame = cap.get(CV_CAP_PROP_FRAME_COUNT);//<获取视频总帧数
	for (int i = 1; i <= totalFrame; i++)
	{
		cap >> frame;
		if (frame.empty())
		{
			cout << "图片为空！" << endl;
			break;
		}
		sprintf(outfile, "E://VS2015Opencv//vs2015//project//视频处理//pic//%d.png", i);
		imwrite(outfile, frame);
		imshow("video", frame);
		waitKey(15);
	}
	cap.release();
	destroyAllWindows();
	return 0;
}

　　

 图片合成视频原理

写入视频；

上面使用Python方法；但是原理一样；

#include<opencv2opencv.hpp>
#include<iostream>

using namespace std;
using namespace cv;

int main()
{

	VideoWriter video("test.avi", CV_FOURCC('X', 'V', 'I', 'D'), 27.0, Size(1280, 720));

	String img_path = "E://VS2015Opencv//vs2015//project//视频处理//pic//";
	vector<String> img;

	glob(img_path, img, false);

	size_t count = img.size();
	for (size_t i = 0; i < count; i++)
	{
		stringstream str;
		str << i << ".png";
		Mat image = imread(img_path + str.str());
		if (!image.empty())
		{
			resize(image, image, Size(1280, 720));
			video << image;
			cout << "正在处理第" << i << "帧" << endl;
		}
	}
	cout << "处理完毕！" << endl;
	waitKey(15);
}

　　

参考：学习OpenCV笔记（二）——图片与视频相互转换

#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <cv.h>
#include <highgui.h>
#define NUM_FRAME 24560 //只处理前300帧，根据需要修改

void Video_to_image(char* filename)
{
	printf("------video to image ------
");
	//读入视频文件
	CvCapture* pCapture = NULL;
	if (!(pCapture = cvCaptureFromFile("pedestrain.avi")))
	{
		printf("Can not open video file
");
		return;
	}

	//逐帧读取文件
	IplImage* pFrame = NULL;
	int i = 0;
	char image_name[50];
	while (i < NUM_FRAME)
	{
		pFrame = cvQueryFrame(pCapture);
		sprintf(image_name, "%s%.5d%s", "image", ++i, ".jpg");//保存的图片名
		cvSaveImage(image_name, pFrame);
		pFrame = NULL;
		//	cvReleaseImage(&pFrame); 
	}
	printf("--------video to image over----------
");

	//	cvReleaseImage(&pFrame);      //释放时出错？！
	cvReleaseCapture(&pCapture);
}

void Image_to_video()
{
	int i = 0;
	IplImage* img = 0;
	char image_name[50];
	printf("-------- image to video --------
");

	CvVideoWriter *writer = 0;
	int isColor = 1;
	int fps = 25;
	int frameW = 640;
	int frameH = 480;

	//创建视频写入器
	//	writer=cvCreateVideoWriter("out.avi",CV_FOURCC('X','V','I','D'),fps,cvSize(frameW,frameH),isColor);
	writer = cvCreateVideoWriter("out.avi", CV_FOURCC('P', 'I', 'M', '1'), fps, cvSize(frameW, frameH), isColor);
	printf("video height : %d
video width : %d
fps : %d
", frameH, frameW, fps);

	//创建视频播放窗口
	//	cvNamedWindow( "mainWin", CV_WINDOW_AUTOSIZE );
	while (i<NUM_FRAME)
	{
		//		sprintf(image_name, "%s%.5d%s", "image", ++i, ".jpg");
		sprintf(image_name, "%s%.5d%s", "AAAOUTPUT_", ++i, ".jpg.jpg");
		img = cvLoadImage(image_name);
		if (!img)  //图片不存在则跳过继续处理下一帧
		{
			//			printf("Could not load image file...
");
			//			img = 0;			
			continue;
		}
		cvShowImage("mainWin", img);
		char key = cvWaitKey(20);
		cvWriteFrame(writer, img);
		//img = NULL;
		cvReleaseImage(&img);

	}
	printf("--------image to video over---------
");
	cvReleaseVideoWriter(&writer);
	cvDestroyWindow("mainWin");
	return;
}

int main(int argc, char *argv[])
{
	//	char *filename = argv[1];
	char filename[50] = "pedestrain.avi";

	//	Video_to_image(filename); 
	Image_to_video();
	return 0;
}