如何在 Windows 应用程序中截取屏幕截图？

Question

如何使用 Win32 截取当前屏幕？

Answer 1

HDC hScreenDC = GetDC(nullptr); // CreateDC("DISPLAY",nullptr,nullptr,nullptr);
HDC hMemoryDC = CreateCompatibleDC(hScreenDC);
int width = GetDeviceCaps(hScreenDC,HORZRES);
int height = GetDeviceCaps(hScreenDC,VERTRES);
HBITMAP hBitmap = CreateCompatibleBitmap(hScreenDC,width,height);
HBITMAP hOldBitmap = static_cast<HBITMAP>(SelectObject(hMemoryDC,hBitmap));
BitBlt(hMemoryDC,0,0,width,height,hScreenDC,0,0,SRCCOPY);
hBitmap = static_cast<HBITMAP>(SelectObject(hMemoryDC,hOldBitmap));
DeleteDC(hMemoryDC);
DeleteDC(hScreenDC);

Answer 2

使用 Windows API 在当前窗口站保存所有监视器的原始 24 位无损位图的完整代码：

BOOL WINAPI SaveBitmap(WCHAR *wPath)
{
    BITMAPFILEHEADER bfHeader;
    BITMAPINFOHEADER biHeader;
    BITMAPINFO bInfo;
    HGDIOBJ hTempBitmap;
    HBITMAP hBitmap;
    BITMAP bAllDesktops;
    HDC hDC, hMemDC;
    LONG lWidth, lHeight;
    BYTE *bBits = NULL;
    HANDLE hHeap = GetProcessHeap();
    DWORD cbBits, dwWritten = 0;
    HANDLE hFile;
    INT x = GetSystemMetrics(SM_XVIRTUALSCREEN);
    INT y = GetSystemMetrics(SM_YVIRTUALSCREEN);

    ZeroMemory(&bfHeader, sizeof(BITMAPFILEHEADER));
    ZeroMemory(&biHeader, sizeof(BITMAPINFOHEADER));
    ZeroMemory(&bInfo, sizeof(BITMAPINFO));
    ZeroMemory(&bAllDesktops, sizeof(BITMAP));

    hDC = GetDC(NULL);
    hTempBitmap = GetCurrentObject(hDC, OBJ_BITMAP);
    GetObjectW(hTempBitmap, sizeof(BITMAP), &bAllDesktops);

    lWidth = bAllDesktops.bmWidth;
    lHeight = bAllDesktops.bmHeight;

    DeleteObject(hTempBitmap);

    bfHeader.bfType = (WORD)('B' | ('M' << 8));
    bfHeader.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
    biHeader.biSize = sizeof(BITMAPINFOHEADER);
    biHeader.biBitCount = 24;
    biHeader.biCompression = BI_RGB;
    biHeader.biPlanes = 1;
    biHeader.biWidth = lWidth;
    biHeader.biHeight = lHeight;

    bInfo.bmiHeader = biHeader;

    cbBits = (((24 * lWidth + 31)&~31) / 8) * lHeight;

    hMemDC = CreateCompatibleDC(hDC);
    hBitmap = CreateDIBSection(hDC, &bInfo, DIB_RGB_COLORS, (VOID **)&bBits, NULL, 0);
    SelectObject(hMemDC, hBitmap);
    BitBlt(hMemDC, 0, 0, lWidth, lHeight, hDC, x, y, SRCCOPY);


    hFile = CreateFileW(wPath, GENERIC_WRITE | GENERIC_READ, 0, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
    WriteFile(hFile, &bfHeader, sizeof(BITMAPFILEHEADER), &dwWritten, NULL);
    WriteFile(hFile, &biHeader, sizeof(BITMAPINFOHEADER), &dwWritten, NULL);
    WriteFile(hFile, bBits, cbBits, &dwWritten, NULL);

    CloseHandle(hFile);

    DeleteDC(hMemDC);
    ReleaseDC(NULL, hDC);
    DeleteObject(hBitmap);

    return TRUE;
}

Answer 3

1. 使用GetDC(NULL); 获取整个屏幕的DC。
2. 使用CreateCompatibleDC创建与屏幕DC兼容的DC。
3. 使用CreateCompatibleBitmap创建与屏幕DC兼容的位图来保存结果。
4. 使用SelectObject 选择兼容位图到兼容DC。
5. 使用BitBlt从屏幕DC复制到兼容的DC。
6. 使用SelectObject 从兼容 DC 中取消选择兼容位图。
7. 使用DeleteDC 删除兼容的DC。

当您创建兼容位图时，您希望它与屏幕 DC 兼容，而不是兼容 DC。

例如：

HDC dcScreen = GetDC(0);
HDC dcTarget = CreateCompatibleDC(dcScreen);
HBITMAP bmpTarget = CreateCompatibleBitmap(dcScreen);
HGDIOBJ oldBmp = SelectObject(dcTarget, bmpTarget);
BitBlt(dcTarget, 0, 0, cx, cy, dcDesktop, x, y, SRCCOPY | CAPTUREBLT);
SelectObject(dcTarget, oldBmp);
DeleteDC(dcTarget);
ReleaseDC(dcScreen);

另一个重要的部分是获取整个虚拟屏幕的大小和位置：

int x  = GetSystemMetrics(SM_XVIRTUALSCREEN);  //left (e.g. -1024)
int y  = GetSystemMetrics(SM_YVIRTUALSCREEN);  //top (e.g. -34)
int cx = GetSystemMetrics(SM_CXVIRTUALSCREEN); //entire width (e.g. 2704)
int cy = GetSystemMetrics(SM_CYVIRTUALSCREEN); //entire height (e.g. 1050)

Answer 4

有一个 MSDN 示例 Capturing an Image，用于将任意 HWND 捕获到 DC（您可以尝试将 GetDesktopWindow 的输出传递给它）。但是这在 Vista/Windows 7 上的新桌面合成器下效果如何，我不知道。

Answer 5

void GetScreenShot(void)
{
    int x1, y1, x2, y2, w, h;

    // get screen dimensions
    x1  = GetSystemMetrics(SM_XVIRTUALSCREEN);
    y1  = GetSystemMetrics(SM_YVIRTUALSCREEN);
    x2  = GetSystemMetrics(SM_CXVIRTUALSCREEN);
    y2  = GetSystemMetrics(SM_CYVIRTUALSCREEN);
    w   = x2 - x1;
    h   = y2 - y1;

    // copy screen to bitmap
    HDC     hScreen = GetDC(NULL);
    HDC     hDC     = CreateCompatibleDC(hScreen);
    HBITMAP hBitmap = CreateCompatibleBitmap(hScreen, w, h);
    HGDIOBJ old_obj = SelectObject(hDC, hBitmap);
    BOOL    bRet    = BitBlt(hDC, 0, 0, w, h, hScreen, x1, y1, SRCCOPY);

    // save bitmap to clipboard
    OpenClipboard(NULL);
    EmptyClipboard();
    SetClipboardData(CF_BITMAP, hBitmap);
    CloseClipboard();   

    // clean up
    SelectObject(hDC, old_obj);
    DeleteDC(hDC);
    ReleaseDC(NULL, hScreen);
    DeleteObject(hBitmap);
}