可以对别的进程的窗口进行操作吗？比如画线，取像素点什么的。

[screen12]

我的程序，创建了另一个进程，能否取那个进程中的一个窗口，然后取得其HDC，然后对其操作，比如画线，用GetPixel()取像素值什么的？

[zgl7903]

可以， 但是进程中如果也有刷新绘制操作，可能会覆盖外部绘制操作

[Eleven]

EnumWindows()/GetWindowThreadProcessId获取进程ID，与你CreateProcess调用获取的PROCESS_INFORMATION中的比对

[schlafenhamster]

例子

void CxxxxDlg::DrawFoundWindow(HWND hWnd)
{
//	int xBorder=GetSystemMetrics(SM_CXBORDER);
	int yBorder=GetSystemMetrics(SM_CYBORDER);
	int xFrame=GetSystemMetrics(SM_CXFRAME);
	int yFrame=GetSystemMetrics(SM_CYFRAME);
	int xScreen=GetSystemMetrics(SM_CXSCREEN);
	int yScreen=GetSystemMetrics(SM_CYSCREEN);
//Windows will restrict your drawing to the client and non-client areas.
	HDC dc=::GetWindowDC(hWnd);// not 0 !
//Create an inverse pen that is the size of a window border.
//	SetROP2(dc,R2_NOT);
//	HPEN newPen=CreatePen(PS_INSIDEFRAME,3*yBorder,0);
//Or real color is "pink" 
	SetROP2(dc,R2_XORPEN);//R2_NOT);
	HPEN newPen=CreatePen(PS_INSIDEFRAME,3*yBorder,RGB(0,255,0));
//
	HPEN oldPen=(HPEN)SelectObject(dc,newPen);
//Rectangle() will not fill in the interior.
	HBRUSH nullBrush=(HBRUSH)GetStockObject(NULL_BRUSH);
	HBRUSH oldBrush=(HBRUSH)SelectObject(dc,nullBrush);
//
	HRGN recvRgn=CreateRectRgn(0,0,0,0);
	if(::GetWindowRgn(hWnd,recvRgn)==RGN_ERROR)
	{//=0 no rgn
		RECT rc;
		::GetWindowRect(hWnd,&rc);
		if(::IsZoomed(hWnd))
		{// zoomed=maximized.
			Rectangle(dc,xFrame,yFrame,xScreen+xFrame,yScreen+yFrame);
		}
		else
		{// not zoomed
			Rectangle(dc,0,0,rc.right-rc.left,rc.bottom-rc.top);
		}
	}
	else //CRgn::CreateFromPath
	{//!=0, has rgn. 
		HBRUSH hatchBrush=CreateHatchBrush(HS_DIAGCROSS,GetSysColor(COLOR_WINDOWFRAME));
		FrameRgn(dc,recvRgn,hatchBrush,xFrame,yFrame);
		DeleteObject(hatchBrush);
	}
// Clean
	DeleteObject(recvRgn);
//
	SelectObject(dc,oldBrush);
	SelectObject(dc,oldPen);
//
	::ReleaseDC(hWnd,dc);
//
	DeleteObject(newPen);
}