摄像头和视频的读取和写入

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我是靠谱客的博主愤怒招牌，这篇文章主要介绍摄像头和视频的读取和写入，现在分享给大家，希望可以做个参考。

总结一下视频的读取和写入，opencv1+和opencv2+以后的版本都总结一下。

先总结一下opencv1+的用法，现在使用的opencv都是2.0以后了，不过1.0版本是使用指针，用起来确实感觉很爽，简单实用。有人不喜欢1.0+的释放控件，我觉得这是个好习惯。

视频读入：

int main(int argc,char* argv[] )
{
	//argv[1] input video file
	//argv[2] name of new output file
	argv[1] = ".../12.mp4";
	CvCapture* capture = NULL;
	capture = cvCreateFileCapture(argv[1]);
	if (!capture)
		return - 1;
	IplImage *bgr_frame = cvQueryFrame(capture);
	//帧率,保证播放的正常速度
	double fps = cvGetCaptureProperty(capture, CV_CAP_PROP_FPS);
	//大小
	CvSize size = cvSize(
		(int)cvGetCaptureProperty(capture, CV_CAP_PROP_FRAME_WIDTH),
		(int)cvGetCaptureProperty(capture, CV_CAP_PROP_FRAME_HEIGHT));
	while ((bgr_frame = cvQueryFrame(capture)) != NULL)//(bgr_frame = cvQueryFrame(capture))!=NULL
	{
		cvNamedWindow("capture", 1);
		cvShowImage("capture", bgr_frame);
		cvWaitKey(fps);
	}
	cvReleaseCapture(&capture);
	cvReleaseImage(&bgr_frame);
	return 0;
}

opencv2.0以后的版本读取方法都是一致的。

int main(int argc, char* argv[])
{
	argv[1] = ".../12.mp4";
	VideoCapture capture(argv[1]);
	if (!capture.isOpened())
	{
		cout << "fail to open" << endl;
		return -1;
	}
	//视频宽高
	Size videoResolution = Size((int)capture.get(CV_CAP_PROP_FRAME_WIDTH),
		(int)capture.get(CV_CAP_PROP_FRAME_HEIGHT));
	//获取视频图像帧率
	double fps = capture.get(CV_CAP_PROP_FPS);
	//视频总帧
	double totalFrame = capture.get(CV_CAP_PROP_FRAME_COUNT);
	cout << "总帧数：" << totalFrame << endl;
	cout << "帧率：" << fps << endl;
	cout << "视频宽、高：" << videoResolution.width << videoResolution.height << endl;
	Mat frameImg;
	while (true)
	{
		capture >> frameImg;
		imshow("frame", frameImg);
		waitKey(fps);
	}
	return 0;
}

opencv1.0+ 写出视频操作，做一个简单的灰度处理吧。opencv1.0有一个需要注意的地方，视频是不是彩色图像的问题，有时候不注意IsColor的参数（默认为1），会造成写出的视频只有6k，出现这种情况就需要考虑是不是忽略了这个问题。

处理过程分三步走：

CvVideoWriter* writer = NULL;
	writer = cvCreateVideoWriter(argv[2], CV_FOURCC('M', 'J', 'P', 'G'), fps, size,0);

while(1)
{
cvWriteFrame(writer, bgr_frame);
}
//释放
cvReleaseVideoWriter(&writer);

灰度化以后在输出就需要注意两个方面，第一，前面说的IsColor必须设置为0，不然写出的视频只有6k。第二，就是定义输出图像的方式，不能直接定义IplImage* gray_frame; 不然在cvCvtColor处理是会出现格式错误。这个是需要注意的，图片深度是8位，1通道。

IplImage* gray_frame = cvCreateImage(size, IPL_DEPTH_8U, 1);

灰度转换，不要用错了：

cvCvtColor(bgr_frame, gray_frame, CV_BGR2GRAY);

//opencv 2.0+的用法

cvtColor(bgr_frame,gray_frame,CV_BGR2GRAY);

完整程序：

int main(int argc,char* argv[] )
{
	//argv[1] input video file
	//argv[2] name of new output file
	argv[1] = ".../12.mp4";
	argv[2] = ".../12out.avi";
	CvCapture* capture = NULL;
	capture = cvCreateFileCapture(argv[1]);
	if (!capture)
		return - 1;
	IplImage *bgr_frame = cvQueryFrame(capture);
	IplImage *gray_frame;
	
	//帧率,保证播放的正常速度
	double fps = cvGetCaptureProperty(capture, CV_CAP_PROP_FPS);
	//大小
	CvSize size = cvSize(
		(int)cvGetCaptureProperty(capture, CV_CAP_PROP_FRAME_WIDTH),
		(int)cvGetCaptureProperty(capture, CV_CAP_PROP_FRAME_HEIGHT));
	gray_frame = cvCreateImage(size, IPL_DEPTH_8U, 1);
	CvVideoWriter* writer = NULL;
	writer = cvCreateVideoWriter(argv[2], CV_FOURCC('M', 'J', 'P', 'G'), fps, size, 0);

	while ((bgr_frame = cvQueryFrame(capture)) != NULL)//(bgr_frame = cvQueryFrame(capture))!=NULL
	{
		cvCvtColor(bgr_frame, gray_frame, CV_BGR2GRAY);
		cvNamedWindow("capture", 1);
		cvShowImage("capture", bgr_frame);
		cvShowImage("gray_grame", gray_frame);
		cvWriteFrame(writer, gray_frame);
		cvWaitKey(fps);
	}
	cvReleaseCapture(&capture);
	cvReleaseImage(&bgr_frame);
	cvReleaseVideoWriter(&writer);
	return 0;
}

效果：

opencv2.0+的视频写出操作：

直接上程序，这种方法很不错，可以选择是否进行压缩。用法是这么用的。

string outputVideoPath = "...\input8Write.avi";
	VideoWriter outputVideo;
Size videoResolution = Size((int)video.get(CV_CAP_PROP_FRAME_WIDTH), (int)video.get(CV_CAP_PROP_FRAME_HEIGHT));
	outputVideo.open(outputVideoPath, -1, 25, videoResolution, true);
while(!frame.empty())
{
outputVideo << image;
}

会打开一个视频压缩方法：

循环读取视频每帧图像时，最好写一个判断，这样写出视频才能跳出，要不然会出现读完视频后，一直留在最后一帧，不会自行跳出。

直接贴上程序：

int main(int argc, char* argv[])
{
	argv[1] = ".../12.mp4";
	VideoCapture capture(argv[1]);
	if (!capture.isOpened())
	{
		cout << "fail to open" << endl;
		return -1;
	}
	//视频宽高
	Size videoResolution = Size((int)capture.get(CV_CAP_PROP_FRAME_WIDTH),
		(int)capture.get(CV_CAP_PROP_FRAME_HEIGHT));
	//获取视频图像帧率
	double fps = capture.get(CV_CAP_PROP_FPS);
	//视频总帧
	double totalFrame = capture.get(CV_CAP_PROP_FRAME_COUNT);
	cout << "总帧数：" << totalFrame << endl;
	cout << "帧率：" << fps << endl;
	cout << "视频宽、高：" << videoResolution.width <<"   "<< videoResolution.height << endl;
	string outputVideoPath = "E:/数学建模/12out2.avi";
	VideoWriter outputVideo;
	outputVideo.open(outputVideoPath, CV_FOURCC('M', 'J', 'P', 'G'), fps, videoResolution, true);
	Mat frameImg,grayImage;
	while (true)
	{
		capture >> frameImg;
		if (!frameImg.empty())
		{
			cvtColor(frameImg, grayImage, CV_BGR2GRAY);
			imshow("frame", frameImg);
			imshow("grayImage", grayImage);
			outputVideo << grayImage;
			waitKey(fps);
		}
		else
		{
			break;
		}
		
	}
	return 0;
}