截取的屏幕图像为什么都是黑的?

[qwedcxza]

我首先建立屏幕 DC

m_ScrDC = CreateDC( "DISPALY", NULL, NULL, NULL );
m_ScrWidth = GetDeviceCaps( m_ScrDC, HORZRES );
m_ScrHigh = GetDeviceCaps( m_ScrDC, VERTRES );
然后从中转化并 bitblt 一个矩形到当前窗口, 蝌蚪是黑的.

是建立屏幕 DC 错误? 还是显示时错误?

[pcman1990]

估计是显示时错误

[TopLevel]

下面是我写的截取指定位置区域屏幕的代码。给你看看。
HBITMAP CSemiTransparent::CreateDesktopBitmap(const POINT &pt, const RECT &rc)
{
CRect rcDesktop( 0, 0, 0, 0 );

// Get the Desktop window size;
GetWindowRect( GetDesktopWindow(), &rcDesktop );

int iScrWidth = rc.right - rc.left; //rcDesktop.Width();
int iScrHeight = rc.bottom - rc.top; //rcDesktop.Height();

// Get the Desktop window dc;
HDC hDesktopDC = GetDC( GetDesktopWindow() );

if ( hDesktopDC == NULL )
{
GetLastError();

return m_hScrBitmap;
}

HDC hMemDeskDC = CreateCompatibleDC( hDesktopDC );

if ( hMemDeskDC == NULL )
{
// Release the Desktop window dc;
ReleaseDC( GetDesktopWindow(), hDesktopDC );

return m_hScrBitmap;
}

m_hScrBitmap = CreateCompatibleBitmap( hDesktopDC, iScrWidth, iScrHeight );

if ( m_hScrBitmap == NULL )
{
// Release the Desktop window dc;
ReleaseDC( GetDesktopWindow(), hDesktopDC );

return m_hScrBitmap;
}

// Store the environmen;
HBITMAP hOldBitmap = (HBITMAP)SelectObject( hMemDeskDC, m_hScrBitmap );

if ( hOldBitmap == NULL )
{
// Delete the memory DC;
DeleteDC( hMemDeskDC );
// Release the Desktop window dc;
ReleaseDC( GetDesktopWindow(), hDesktopDC );

return m_hScrBitmap;

}

if ( BitBlt( hMemDeskDC,
0,
0,
iScrWidth,
iScrHeight,
hDesktopDC,
pt.x,
pt.y,
SRCCOPY
) == FALSE )
{
// Restore the environment.
SelectObject( hMemDeskDC, hOldBitmap );
// Delete the memory DC;
DeleteDC( hMemDeskDC );
// Release the Desktop window dc;
ReleaseDC( GetDesktopWindow(), hDesktopDC );

return m_hScrBitmap;

}

// Restore the environment.
m_hScrBitmap = (HBITMAP)SelectObject( hMemDeskDC, hOldBitmap );
// Delete the memory DC;
DeleteDC( hMemDeskDC );
// Release the Desktop window dc;
ReleaseDC( GetDesktopWindow(), hDesktopDC );


return m_hScrBitmap;
}
不用加注释了吧。
：）

[msl]

估计你CreateCompatibleBitmap的时候DC参数不正确，你创建的位图为黑白位图，因而系统在帮你转换过来的时候，全部编程黑色。（我说的可能不对）

[qwedcxza]

为什么要中转那么多层呢? 我只需要将屏幕转到当前窗口的 DC.

谢谢了! 可奇怪的是? 显示不出鼠标移动? 但鼠标点击的变化可以看到!!