Question

我一直在编写一些代码来执行窗口的屏幕抓取（在Windows中）。代码工作正常，但是在屏幕抓取之前我必须将窗口移到我想捕获的前面并强制重绘。

我强制使用InvalidateRect重绘，然后我必须从消息循环中抽取一些消息，以便处理WM_PAINT。这显然有点蹩脚，因为我不知道要输出多少消息。

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，并且似乎不会重绘其所有的孩子。

所以我的问题是，是否有更好的方法在屏幕抓取之前重绘窗口？

干杯富

Answer 1

由于您没有提到您正在使用的语言，我希望C ++中的以下代码可以帮助您！

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 );
}

你实际上并不需要强制重绘..但是在窗口最小化的情况下，你可能需要启动它，然后用窗口句柄调用函数..！ texWidth和texHeight是您要捕获的窗口的尺寸;要获得此功能，您可以使用，GetWindowRect（..）或查看此处的链接：link

屏幕抓取一个窗口

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