C++如何实现截图截屏

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1、截图工具

1.1 键盘截图(PrtScn键)

如何使用Microsoft Windows操作系统中的Print Screen（打印屏幕）键
（1）Print Screen键
按下之后，截取整个屏幕的画面到剪切板里。可以复制到其他软件里，比如系统的画图工具，Office Word等。

（2）Alt+Print Screen组合键
按下之后，截取当前活动窗口的画面到剪切板里。

1.2 win10自带截图(Win+Shift+S)

按下该组合键之后，使用鼠标在屏幕上画出想要截取的矩形区域，自动保存到系统剪切板里。

1.3 系统自带的截图小工具

1.4 ffmpeg

ffmpeg -i "输入视频" -fflags nobuffer -t 60 -ss 0 "输出地址"
说明：代表截取输入视频从0秒到60秒的片段，保存到输出地址。
-ss n : 起始时间为第n秒
-t n : 总共截取的片段时长为n秒

运行后会生成截图： out1.jpg out2.jpg out3.jpg …

ffmpeg -i fight.mp4 -r 1 -t 200 -ss 1 -f image2 out%d.jpg

1.5 ScreenToGif

1.6 Chrome

2、C++、GDI

2.1 微软官方例子

https://docs.microsoft.com/en-us/windows/win32/gdi/capturing-an-image

int CaptureAnImage(HWND hWnd){    HDC hdcScreen;    HDC hdcWindow;    HDC hdcMemDC = NULL;    HBITMAP hbmScreen = NULL;    BITMAP bmpScreen;    DWORD dwBytesWritten = 0;    DWORD dwSizeofDIB = 0;    HANDLE hFile = NULL;    char* lpbitmap = NULL;    HANDLE hDIB = NULL;    DWORD dwBmpSize = 0;    // Retrieve the handle to a display device context for the client     // area of the window.     hdcScreen = GetDC(NULL);    hdcWindow = GetDC(hWnd);    // Create a compatible DC, which is used in a BitBlt from the window DC.    hdcMemDC = CreateCompatibleDC(hdcWindow);    if (!hdcMemDC)    {        MessageBox(hWnd, L"CreateCompatibleDC has failed", L"Failed", MB_OK);        goto done;    }    // Get the client area for size calculation.    RECT rcClient;    GetClientRect(hWnd, &rcClient);    // This is the best stretch mode.    SetStretchBltMode(hdcWindow, HALFTONE);    // The source DC is the entire screen, and the destination DC is the current window (HWND).    if (!StretchBlt(hdcWindow,        0, 0,        rcClient.right, rcClient.bottom,        hdcScreen,        0, 0,        GetSystemMetrics(SM_CXSCREEN),        GetSystemMetrics(SM_CYSCREEN),        SRCCOPY))    {        MessageBox(hWnd, L"StretchBlt has failed", L"Failed", MB_OK);        goto done;    }    // Create a compatible bitmap from the Window DC.    hbmScreen = CreateCompatibleBitmap(hdcWindow, rcClient.right - rcClient.left, rcClient.bottom - rcClient.top);    if (!hbmScreen)    {        MessageBox(hWnd, L"CreateCompatibleBitmap Failed", L"Failed", MB_OK);        goto done;    }    // Select the compatible bitmap into the compatible memory DC.    SelectObject(hdcMemDC, hbmScreen);    // Bit block transfer into our compatible memory DC.    if (!BitBlt(hdcMemDC,        0, 0,        rcClient.right - rcClient.left, rcClient.bottom - rcClient.top,        hdcWindow,        0, 0,        SRCCOPY))    {        MessageBox(hWnd, L"BitBlt has failed", L"Failed", MB_OK);        goto done;    }    // Get the BITMAP from the HBITMAP.    GetObject(hbmScreen, sizeof(BITMAP), &bmpScreen);    BITMAPFILEHEADER   bmfHeader;    BITMAPINFOHEADER   bi;    bi.biSize = sizeof(BITMAPINFOHEADER);    bi.biWidth = bmpScreen.bmWidth;    bi.biHeight = bmpScreen.bmHeight;    bi.biPlanes = 1;    bi.biBitCount = 32;    bi.biCompression = BI_RGB;    bi.biSizeImage = 0;    bi.biXPelsPerMeter = 0;    bi.biYPelsPerMeter = 0;    bi.biClrUsed = 0;    bi.biClrImportant = 0;    dwBmpSize = ((bmpScreen.bmWidth * bi.biBitCount + 31) / 32) * 4 * bmpScreen.bmHeight;    // Starting with 32-bit Windows, GlobalAlloc and LocalAlloc are implemented as wrapper functions that     // call HeapAlloc using a handle to the process's default heap. Therefore, GlobalAlloc and LocalAlloc     // have greater overhead than HeapAlloc.    hDIB = GlobalAlloc(GHND, dwBmpSize);    lpbitmap = (char*)GlobalLock(hDIB);    // Gets the "bits" from the bitmap, and copies them into a buffer     // that's pointed to by lpbitmap.    GetDIBits(hdcWindow, hbmScreen, 0,        (UINT)bmpScreen.bmHeight,        lpbitmap,        (BITMAPINFO*)&bi, DIB_RGB_COLORS);    // A file is created, this is where we will save the screen capture.    hFile = CreateFile(L"captureqwsx.bmp",        GENERIC_WRITE,        0,        NULL,        CREATE_ALWAYS,        FILE_ATTRIBUTE_NORMAL, NULL);    // Add the size of the headers to the size of the bitmap to get the total file size.    dwSizeofDIB = dwBmpSize + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);    // Offset to where the actual bitmap bits start.    bmfHeader.bfOffBits = (DWORD)sizeof(BITMAPFILEHEADER) + (DWORD)sizeof(BITMAPINFOHEADER);    // Size of the file.    bmfHeader.bfSize = dwSizeofDIB;    // bfType must always be BM for Bitmaps.    bmfHeader.bfType = 0x4D42; // BM.    WriteFile(hFile, (LPSTR)&bmfHeader, sizeof(BITMAPFILEHEADER), &dwBytesWritten, NULL);    WriteFile(hFile, (LPSTR)&bi, sizeof(BITMAPINFOHEADER), &dwBytesWritten, NULL);    WriteFile(hFile, (LPSTR)lpbitmap, dwBmpSize, &dwBytesWritten, NULL);    // Unlock and Free the DIB from the heap.    GlobalUnlock(hDIB);    GlobalFree(hDIB);    // Close the handle for the file that was created.    CloseHandle(hFile);    // Clean up.done:    DeleteObject(hbmScreen);    DeleteObject(hdcMemDC);    ReleaseDC(NULL, hdcScreen);    ReleaseDC(hWnd, hdcWindow);    return 0;}

2.2 C++、GDI、CImage

HDC hdcSrc = GetDC(NULL);int nBitPerPixel = GetDeviceCaps(hdcSrc, BITSPIXEL);int nWidth = GetDeviceCaps(hdcSrc, HORZRES);int nHeight = GetDeviceCaps(hdcSrc, VERTRES);CImage image;image.Create(nWidth, nHeight, nBitPerPixel);BitBlt(image.GetDC(), 0, 0, nWidth, nHeight, hdcSrc, 0, 0, SRCCOPY);ReleaseDC(NULL, hdcSrc);image.ReleaseDC();image.Save(s, Gdiplus::ImageFormatPNG);

3、C++、OpenGL

void CaptureOpenGLWindow(const char* savePath, int w, int h){        GLubyte* pPixelData;         GLint    PixelDataLength;          // 分配内存和打开文件        pPixelData = (GLubyte*)malloc(w*h*3);        if (pPixelData == 0)                return;                glPixelStorei(GL_UNPACK_ALIGNMENT, 4);         glReadPixels(0, 0, w, h, GL_RGB, GL_UNSIGNED_BYTE, pPixelData);        stbi_write_png(savePath, w, h, 3, pPixelData, 0);        free(pPixelData);        int iw = w, ih = h, n = 3;        stbi_set_flip_vertically_on_load(true);        unsigned char *idata = stbi_load(savePath, &iw, &ih, &n, 0);        stbi_write_png(savePath, w, h, 3, idata, 0);        stbi_image_free(idata);}

4、C++、OpenCV

BITMAPINFOHEADER createBitmapHeader(int width, int height){   BITMAPINFOHEADER  bi;     // create a bitmap     bi.biSize = sizeof(BITMAPINFOHEADER);     bi.biWidth = width;     bi.biHeight = -height;  //this is the line that makes it draw upside down or not     bi.biPlanes = 1;     bi.biBitCount = 32;     bi.biCompression = BI_RGB;     bi.biSizeImage = 0;     bi.biXPelsPerMeter = 0;     bi.biYPelsPerMeter = 0;     bi.biClrUsed = 0;     bi.biClrImportant = 0;     return bi;}Mat captureScreenMat(HWND hwnd){     Mat src;     // get handles to a device context (DC)     HDC hwindowDC = GetDC(hwnd);     HDC hwindowCompatibleDC = CreateCompatibleDC(hwindowDC);     SetStretchBltMode(hwindowCompatibleDC, COLORONCOLOR);     // define scale, height and width     int screenx = GetSystemMetrics(SM_XVIRTUALSCREEN);     int screeny = GetSystemMetrics(SM_YVIRTUALSCREEN);     int width = GetSystemMetrics(SM_CXVIRTUALSCREEN);     int height = GetSystemMetrics(SM_CYVIRTUALSCREEN);     // create mat object     src.create(height, width, CV_8UC4);     // create a bitmap     HBITMAP hbwindow = CreateCompatibleBitmap(hwindowDC, width, height);     BITMAPINFOHEADER bi = createBitmapHeader(width, height);     // use the previously created device context with the bitmap     SelectObject(hwindowCompatibleDC, hbwindow);     // copy from the window device context to the bitmap device context     StretchBlt(hwindowCompatibleDC, 0, 0, width, height, hwindowDC, screenx, screeny, width, height, SRCCOPY);  //change SRCCOPY to NOTSRCCOPY for wacky colors !     GetDIBits(hwindowCompatibleDC, hbwindow, 0, height, src.data, (BITMAPINFO*)&bi, DIB_RGB_COLORS);            //copy from hwindowCompatibleDC to hbwindow     // avoid memory leak     DeleteObject(hbwindow);     DeleteDC(hwindowCompatibleDC);     ReleaseDC(hwnd, hwindowDC);     return src; } int main(){      // capture image      HWND hwnd = GetDesktopWindow();      Mat src = captureScreenMat(hwnd);      // save img      cv::imwrite("Screenshot.png", src);        // clean-ups      buf.clear();      return 0;}

5、C++、QT

QDesktopWidget *desk = QApplication::desktop();QScreen * screen = QGuiApplication::primaryScreen();QPixmap p = screen->grabWindow(desk->winId());QImage image = p.toImage();

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