学习OpenCV(三十一) -- 视频处理

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double cvGetCaptureProperty( CvCapture* capture, int property_id );

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int cvSetCaptureProperty( CvCapture* capture, int property_id, double value );

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typedef struct CvVideoWriter CvVideoWriter;
CvVideoWriter* cvCreateVideoWriter( const char* filename, int fourcc, double fps, CvSize frame_size, int is_color=1 );

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int cvWriteFrame( CvVideoWriter* writer, const IplImage* image );

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void cvReleaseVideoWriter( CvVideoWriter** writer );

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/*
视频处理
*/

#include"cv.h"
#include"highgui.h"
//播放一段视频
void main()
{
	cvNamedWindow("tree", CV_WINDOW_AUTOSIZE);
	IplImage* frame;
	CvCapture* capture = cvCreateFileCapture("tree.avi");
	while(1)
	{
		frame = cvQueryFrame(capture); //从文件中抓取或返回一帧
		if(!frame)
			break;
		cvShowImage("tree", frame);
		char c = cvWaitKey(33);
		if(c == 27)
			break;
	}

	cvReleaseCapture(&capture);
	cvDestroyWindow("tree");
}

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/*
视频控制
*/

#include "cv.h"
#include "highgui.h"

//通过添加一个全局变量表示滚动条的位置
//并添加一个回调函数更新变量以及重新设置视频读入的位置
int g_slider_position = 0; //在全局变量前面加g_
CvCapture* g_capture  = NULL;

//定义回调函数
//在滚动条拖动时调用，滚动条的位置会被作为一个32位的整数以参数形式传入
void onTrackbarSlide(int pos)
{
	cvSetCaptureProperty( //与cvGetCaptureProperty一起使用，可以设置（查询）CvCapture对象的各种属性
		g_capture,
		CV_CAP_PROP_POS_FRAMES, //以帧数设置读入位置
		pos
		);
}

//用opencv播放avi视频
int main()
{
	cvNamedWindow("tree",CV_WINDOW_AUTOSIZE); 
	// CvCapture这个结构体
	//CvCapture* capture= cvCreateFileCapture("start.avi"); //读入avi文件，返回一个指向CvCapture的指针 
	g_capture= cvCreateFileCapture("tree.avi");
	int frames = (int) cvGetCaptureProperty(
		g_capture,
		CV_CAP_PROP_FRAME_COUNT
		);
	if( frames!= 0)
	{
		cvCreateTrackbar(
			"Position",
			"tree",
			&g_slider_position,
			frames,
			onTrackbarSlide
			);
	}
	IplImage* frame;
	while(1){
		frame = cvQueryFrame(g_capture);//将下一帧视频文件载入内存
		if(!frame) break;
		cvShowImage("tree",frame);
		char c=cvWaitKey(33);
		if(c==27)break;  //ESC键的ASCII编码是27
	}
	cvReleaseCapture(&g_capture);//释放空间
	cvDestroyWindow("tree");
	return(0);
}

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/*
完整的视频程序
*/

#include "cv.h"
#include "highgui.h"

int main()
{
	CvCapture* capture = 0;
	capture = cvCreateFileCapture("tree.avi");
	if(!capture)
	{
		return -1;
	}
	IplImage* bgr_frame = cvQueryFrame(capture);
	double fps = cvGetCaptureProperty(
		capture,
		CV_CAP_PROP_FPS
		);
	CvSize size = cvSize(
		(int)cvGetCaptureProperty(capture, CV_CAP_PROP_FRAME_WIDTH),
		(int)cvGetCaptureProperty(capture, CV_CAP_PROP_FRAME_HEIGHT)
		);
	CvVideoWriter *writer = cvCreateVideoWriter(
		"tree1.avi",
		CV_FOURCC('M','J','P','G'),
		fps,
		size
		);
	IplImage* logpolar_frame = cvCreateImage(
		size,
		IPL_DEPTH_8U,
		3
		);
	cvNamedWindow("tree", CV_WINDOW_AUTOSIZE);
	while( (bgr_frame = cvQueryFrame(capture)) != NULL)
	{
		cvLogPolar(bgr_frame, logpolar_frame,
			cvPoint2D32f(bgr_frame->width/2, bgr_frame->height/2),
			40,
			CV_INTER_LINEAR + CV_WARP_FILL_OUTLIERS
			);
		cvWriteFrame(writer, logpolar_frame);
		cvShowImage("tree",logpolar_frame);
		char c = cvWaitKey(33);
		if(c==27) break;
	}
	cvReleaseVideoWriter(&writer);
	cvReleaseImage(&logpolar_frame);
	cvReleaseCapture(&capture);
	return(0);
}