如何从HWND中删除以前的图像数据

我正在使用GDI +绘制具有透明度的png图像。



过了一段时间我想用一些旋转绘制相同的图像。但我无法删除上一个图像日期。所以我渲染的窗口是一系列旧图像。

I am using GDI+ to draw png image with transparency.

after sometime I want to draw same image with some rotation. but I am not able to remove The previous image date. So my rendered window is a series of old images.

void CBusyWnd::drawImage	( )
{
	if (mImage)
	{
		Gdiplus::Graphics gdip(mWnd);
		gdip.ResetTransform();
		gdip.TranslateTransform((Gdiplus::REAL)(mImage->GetWidth())/2.0f,(Gdiplus::REAL)(mImage->GetHeight())/2.0f);
		gdip.RotateTransform(mAngle=mAngle>360?0:mAngle+1);
		gdip.TranslateTransform(-1.0f*(Gdiplus::REAL)(mImage->GetWidth())/2.0f,-1.0f*(Gdiplus::REAL)(mImage->GetHeight())/2.0f);
		gdip.DrawImage(mImage, 0, 0, mImage->GetWidth(), mImage->GetHeight());
		gdip.Flush();
	}
	InvalidateRect(mWnd, NULL, FALSE);
}

请在http://social.msdn.microsoft.com/Forums/en-US/vcgeneral/thread/825a5243-9441-4abc-be30-e5598ccc9872 [ ^ ]



我的注册窗口类是： -

please find image at http://social.msdn.microsoft.com/Forums/en-US/vcgeneral/thread/825a5243-9441-4abc-be30-e5598ccc9872[^]

my registered window class is:-

outWndClass.style		= CS_HREDRAW | CS_VREDRAW;
outWndClass.lpfnWndProc		= wndProc; 
outWndClass.hInstance		= GetModuleHandle(NULL);
outWndClass.hCursor		= LoadCursor(NULL, IDC_APPSTARTING);
outWndClass.hbrBackground	= (HBRUSH)GetStockObject(HOLLOW_BRUSH);//(HBRUSH)(COLOR_WINDOW + 1);
outWndClass.lpszClassName	= L"BusyWnd";

outWndClass.hIcon		= LoadIcon(outWndClass.hInstance, MAKEINTRESOURCE(IDI_APPLICATION));


if (!RegisterClass(&outWndClass))
{
	if (GetLastError() != 0x00000582) // already registered)
	{
		OutputDebugString(L"Unable to register class BusyWnd\n");
		return false;
	}
}

任何人都可以帮我一些指针。



我尝试在每次抽奖前使用以下代码清除窗口。但代码太慢，无法设置透明度。

Can anyone help give me some pointer.

I tried following code for clearing the window before each draw. but Code is too slow and the is no way to set transparency.

HDC hdc = GetDC(mWnd); // Get the DC from that HWND
for( UINT i = 0 ; i < mImage->GetWidth() ; i++ )
	for( UINT j = 0 ; j < mImage->GetHeight() ; j++ )
		SetPixel(hdc, i,j, RGB(255,255,255)); // SetPixel(HDC hdc, int x, int y, COLORREF color)
ReleaseDC(mWnd, hdc); // Release the DC
DeleteDC(hdc); // Delete the DC