OpenCV实现简单录屏功能
时间：2022-12-28 09:40:30|栏目：C代码|点击： 次
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
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）
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。
#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;
}
