本文实例为大家分享了OpenCV实现简单录屏功能的具体代码，供大家参考，具体内容如下
OpenCV中VideoCapture和VideoWriter用于读写视频文件，这里的录屏功能用到VideoWriter，用于将捕获的屏幕的每一帧数据保存到视频文件。
VideoWriter写视频文件的步骤
1、bool open(const String& filename, int fourcc, double fps,Size frameSize, bool isColor = true);
2、void write(InputArray image);或者VideoWriter& operator << (const Mat& image);
3、void release();
下列代码用于获取屏幕的截图
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int width = GetSystemMetrics(SM_CXSCREEN);int height = GetSystemMetrics(SM_CYSCREEN);HDC hdcScreen = GetDC(NULL);HDC hdcMemDC = CreateCompatibleDC(hdcScreen);HBITMAP hbmScreen = CreateCompatibleBitmap(hdcScreen, width, height); BITMAPINFO bi;bi.bmiHeader.biSize = sizeof(bi.bmiHeader);bi.bmiHeader.biWidth = width;bi.bmiHeader.biHeight = height;bi.bmiHeader.biPlanes = 1;bi.bmiHeader.biBitCount = 24;bi.bmiHeader.biCompression = BI_RGB;bi.bmiHeader.biSizeImage = 0;bi.bmiHeader.biXPelsPerMeter = 0;bi.bmiHeader.biYPelsPerMeter = 0;bi.bmiHeader.biClrUsed = 0;bi.bmiHeader.biClrImportant = 0;SelectObject(hdcMemDC, hbmScreen);int lineBytes = ((width * bi.bmiHeader.biBitCount + 31) / 32) * 4;//每行字节数必须是4字节的整数倍int bmpSize = lineBytes * height;char* lpbitmap = new char[bmpSize];BitBlt(hdcMemDC, 0, 0, width, height, hdcScreen, 0, 0, SRCCOPY);GetDIBits(hdcMemDC, hbmScreen, 0, height, lpbitmap, &bi, DIB_RGB_COLORS); |
lpbitmap为屏幕的像素颜色数据，下列代码将lpbitmap作为一帧写到视频中（假设VideoWriter为已正常打开的VideoWriter实例）
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cv::Mat bmpMat(height, width, CV_8UC3);for (int i = 0; i < height; i++){ int srcIndex = (height-i-1) * lineBytes; int destIndex = i * width * 3; memcpy(&bmpMat.data[destIndex],&lpbitmap[srcIndex],width*3);}videoWriter.write(bmpMat);//或videoWriter << bmpMat; |
因为lpbitmap中的数据是从左下角到右上角排列，而视频帧图像的数据是从左上角到右下角排列，所以要将数据按行上下翻转，即lpbitmap第一行对应视频图像的最后一行。另外BMP图像数据每行的字节数必须是4字节的整数倍，而写入视频的Mat数据没有这个要求，即每行数据大小是图像实际宽度乘以每个颜色占用的字节数，所以实际每行拷贝的数据是width*3节字。
下面是一段测试代码，这里只录制100帧，实际使用中可通过命令行参数、快捷键或按钮等自行决定开始和结束时间，帧率这里也设为固定的25，其实也应该根据具体形况设定合适的值。最后别忘了将opencv_ffmpegXXX.dll文件放到可执行文件目录下。
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#include<windows.h>#include"opencv2/opencv.hpp"int main(){ cv::VideoWriter videoWriter; double fps = 25; int codec = cv::VideoWriter::fourcc('m', 'p', '4', 'v'); int width = GetSystemMetrics(SM_CXSCREEN); int height = GetSystemMetrics(SM_CYSCREEN); time_t seconds = time(0); int s = seconds % 60; int m = (seconds % 3600) / 60; int h = (seconds % (3600 * 24)) / 3600 + 8; char timeBuf[128] = { 0 }; sprintf_s(timeBuf, "CaptureScreen-%d-%d-%d.mp4", h, m, s); cv::String filePath = timeBuf; videoWriter.open(filePath, codec, fps, cv::Size(width, height), true); if (!videoWriter.isOpened()) { return -1; } HDC hdcScreen = GetDC(NULL); HDC hdcMemDC = CreateCompatibleDC(hdcScreen); HBITMAP hbmScreen = CreateCompatibleBitmap(hdcScreen, width, height); BITMAPINFO bi; bi.bmiHeader.biSize = sizeof(bi.bmiHeader); bi.bmiHeader.biWidth = width; bi.bmiHeader.biHeight = height; bi.bmiHeader.biPlanes = 1; bi.bmiHeader.biBitCount = 24; bi.bmiHeader.biCompression = BI_RGB; bi.bmiHeader.biSizeImage = 0; bi.bmiHeader.biXPelsPerMeter = 0; bi.bmiHeader.biYPelsPerMeter = 0; bi.bmiHeader.biClrUsed = 0; bi.bmiHeader.biClrImportant = 0; SelectObject(hdcMemDC, hbmScreen); int lineBytes = ((width * bi.bmiHeader.biBitCount + 31) / 32) * 4; int bmpSize = lineBytes * height; char* lpbitmap = new char[bmpSize]; cv::Mat bmpMat(height, width, CV_8UC3); for (int i=0;i<100;i++) { if (BitBlt(hdcMemDC, 0, 0, width, height, hdcScreen, 0, 0, SRCCOPY)) { GetDIBits(hdcMemDC, hbmScreen, 0, height, lpbitmap, &bi, DIB_RGB_COLORS); for (int i = 0; i < height; i++) { int srcIndex = (height-i-1) * lineBytes; int destIndex = i * width * 3; memcpy(&bmpMat.data[destIndex],&lpbitmap[srcIndex],width*3); } videoWriter.write(bmpMat);//videoWriter << bmpMat; } } delete[] lpbitmap; if (videoWriter.isOpened()) { videoWriter.release(); } return 0;} |
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持服务器之家。
原文链接：https://blog.csdn.net/yb0022/article/details/100893722
