如何在Windows应用程序中截取屏幕截图？

Question

如何使用Win32截取当前屏幕的屏幕截图？

Answer 1

// get the device context of the screen
HDC hScreenDC = CreateDC("DISPLAY", NULL, NULL, NULL);     
// and a device context to put it in
HDC hMemoryDC = CreateCompatibleDC(hScreenDC);

int width = GetDeviceCaps(hScreenDC, HORZRES);
int height = GetDeviceCaps(hScreenDC, VERTRES);

// maybe worth checking these are positive values
HBITMAP hBitmap = CreateCompatibleBitmap(hScreenDC, width, height);

// get a new bitmap
HBITMAP hOldBitmap = (HBITMAP) SelectObject(hMemoryDC, hBitmap);

BitBlt(hMemoryDC, 0, 0, width, height, hScreenDC, 0, 0, SRCCOPY);
hBitmap = (HBITMAP) SelectObject(hMemoryDC, hOldBitmap);

// clean up
DeleteDC(hMemoryDC);
DeleteDC(hScreenDC);

// now your image is held in hBitmap. You can save it or do whatever with it

Answer 2

1. 使用GetDC(NULL);得到一个DC在整个屏幕.
2. 使用CreateCompatibleDC创建与屏幕DC兼容的DC.
3. 使用CreateCompatibleBitmap创建与屏幕DC容纳结果兼容的位图.
4. 用于SelectObject在兼容的DC中选择兼容的位图.
5. 用于BitBlt从屏幕DC复制到兼容的DC.
6. 用于SelectObject从兼容的DC中取消选择兼容的位图.
7. 使用DeleteDC删除兼容DC.

创建兼容位图时,您希望它与屏幕DC兼容,而不是兼容的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 3

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);
}

Answer 4

使用 Windows API 在当前窗口站保存所有显示器的原始 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 5

有一个MSDN示例，“ 捕获图像”，用于将任意HWND捕获到DC（您可以尝试将GetDesktopWindow的输出传递给DC）。但是我不知道这在Vista / Windows 7上的新桌面合成器下将如何运作。