windows - 窗口的屏幕截图

Question

我一直在编写一些代码来抓取窗口的屏幕(在 Windows 中)。代码工作正常，但是在屏幕抓取之前，我必须将窗口带到我想要捕获的前面并强制重绘。

我用 InvalidateRect 强制重绘，然后我必须从消息循环中提取一些消息以便 WM_PAINT 得到处理。这显然有点蹩脚，因为我不知道要发送多少消息。

我尝试将 RedrawWindow 与 RDW_ALLCHILDREN 一起使用，但是我从中抓取屏幕的应用程序是一个 MDI 应用程序，似乎并没有重绘它的所有子项。

所以我的问题是，有没有更好的方法在屏幕抓取之前重绘窗口？

干杯丰富

Answer 1

由于您没有提到您使用的语言，我希望以下 C++ 代码对您有所帮助!

void getScreenShot( int texWidth, int texHeight, unsigned char* pBuffer, HWND handle )
{
    /* Local variables */
    HDC screenDC;
    RECT screenRect;
    int extraBytesPerRow;
    BITMAPINFO bitmapInfo;
    HDC bitmapDC;
    void* bitmapDataPtr;
    HBITMAP hBitmap;
    HBITMAP hPrevBitmap;
    unsigned char* pIn;
    unsigned char* pOut;
    int rowIndex;
    int colIndex;
    /* Get a DC from the desktop window */
    screenDC = GetDC(handle);
    GetClientRect(handle, &screenRect );
    /* Determine the extra bytes we need per row (each row of bitmap data must end on a 32bit boundary) */
    extraBytesPerRow = ( texWidth * 3 ) % 4;
    extraBytesPerRow = extraBytesPerRow ? 4 - extraBytesPerRow : 0;
    /* Setup the bitmap info structure */
    memset( &bitmapInfo, 0, sizeof( bitmapInfo ) );
    bitmapInfo.bmiHeader.biSize = sizeof( BITMAPINFOHEADER );
    bitmapInfo.bmiHeader.biWidth = texWidth;
    bitmapInfo.bmiHeader.biHeight = texHeight;
    bitmapInfo.bmiHeader.biPlanes = 1;
    bitmapInfo.bmiHeader.biBitCount = 24;
    bitmapInfo.bmiHeader.biCompression = BI_RGB;
    /* Create a bitmap device context (bitmapDataPtr will be a pointer to the bits in the bitmap) */
    bitmapDC = CreateCompatibleDC( NULL );
    hBitmap = CreateDIBSection( bitmapDC, ( BITMAPINFO* )&bitmapInfo.bmiHeader, DIB_RGB_COLORS, &bitmapDataPtr, NULL, 0 );
    hPrevBitmap = ( HBITMAP )SelectObject( bitmapDC, hBitmap );
    /* BitBlt or StretchBlt the image from the input DC into our bitmap DC */
    if ( ( texWidth != screenRect.right ) || ( texHeight != screenRect.bottom ) )
    {
        SetStretchBltMode( bitmapDC, HALFTONE );
        StretchBlt( bitmapDC, 0, 0, texWidth, texHeight, screenDC, 0, 0, screenRect.right, screenRect.bottom, SRCCOPY );
    }
    else
    {
        BitBlt( bitmapDC, 0, 0, texWidth, texHeight, screenDC, 0, 0, SRCCOPY);
    }
    /* Copy the data from the bitmap to the user's buffer (bitmap data is BGR and 4 byte aligned on each row, we want tightly-packed RGB) */
    pIn = ( unsigned char* )bitmapDataPtr;
    pOut = pBuffer;
    for ( rowIndex = 0; rowIndex < texHeight; rowIndex++ )
    {
        for ( colIndex = 0; colIndex < texWidth; colIndex++ )
        {
            pOut[ 0 ] = pIn[2];
            pOut[ 1 ] = pIn[1];
            pOut[ 2 ] = pIn[0];
            pOut += 3;
            pIn += 3;
        }
        pIn += extraBytesPerRow;
    }
    /* Free memory used by the bitmap */
    SelectObject( bitmapDC, hPrevBitmap );
    DeleteObject( hBitmap );
    DeleteDC( bitmapDC );
    /* Release the screen DC */
    ReleaseDC(handle, screenDC );
}

您实际上不需要强制重绘..但是如果窗口最小化，您可能需要在使用窗口句柄调用函数之前将其调出..! texWidth 和 texHeight 是您要捕获的窗口的尺寸；要获得此信息，您可以使用 GetWindowRect(..) 或查看此处的链接:link