How to get pixels from window using Direct2D

问题

My problem is getting the pixels in a window. I can't find a way to do this. I using standard windows functions and Direct2D (not DirectDraw). I am using standard initialization of new window:

WNDCLASS wc;
wc.style = CS_OWNDC; 
wc.lpfnWndProc = WndProc; 
wc.cbClsExtra = 0;
wc.cbWndExtra = 0;
wc.hInstance = hInstance;
wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
wc.hCursor = LoadCursor(NULL, IDC_ARROW); wc.hbrBackground = (HBRUSH)(6);   
wc.lpszMenuName = 0;
wc.lpszClassName = L"WINDOW"; RegisterClass(&wc); 
hWnd = CreateWindow(L"WINDOW", L"Game", WS_OVERLAPPEDWINDOW,100,100,1024,768,NULL,NULL,hInstance,NULL);

Then I create a D2D1factory object and draw the bitmap in the window:

HWND hWnd = NULL;
srand((unsigned int)time((time_t)NULL));

ID2D1Factory* factory = NULL;
ID2D1HwndRenderTarget* rt = NULL;
CoInitializeEx(NULL,COINIT_MULTITHREADED);
My_CreateWindow(&hWnd, hInstance);
My_CreateFactory(&hWnd, factory, rt);
D2D1CreateFactory(D2D1_FACTORY_TYPE_SINGLE_THREADED,&factory);

factory->CreateHwndRenderTarget(RenderTargetProperties(), HwndRenderTargetProperties(hWnd,SizeU(800,600)), &rt);

// tons of code

rt->BeginDraw(); rt->DrawBitmap(background[0], RectF(0,0,800,600));
rt->DrawBitmap(GIFHorse[(int)iterator],
RectF(0+MyX-100,0+MyY-100,100+MyX,100+MyY));
rt->DrawBitmap(Star[(int)iterator], RectF(0 + starX, 0 + starY, 50 + starX, 50+starY)); rt->EndDraw();

I need to calculate the hits (I am trying to make simple game). So that's why I need access to all pixels in window.

I'm thinking about using other algorithms, but they're harder to make and I want to start with something easier.

I know about the GetPixel() function, but I cant understand what I should use for HDC.

回答1:

There is no simple and easy way to get to D2D pixels.

A simple collision detection can be implemented using geometries. If you have outlines of your objects in ID2D1Geometry objects you can compare them using ID2D1Geometry::CompareWithGeometry.

If you insist on the pixels, a way to access them is from the DC obtainable via IDXGISurface1::GetDC

In this case you need to use the DXGI surface render target and the swap chain instead of the hwnd render target.

Step by step:

1. D3D11CreateDeviceAndSwapChain gives you the swap chain.
2. IDXGISwapChain::GetBuffer gives you the DXGI surface.
3. ID2D1Factory::CreateDxgiSurfaceRenderTarget gives you the render target.
4. IDXGISurface1::GetDC gives you the DC. Read the remarks on this page!

来源：https://stackoverflow.com/questions/23686096/how-to-get-pixels-from-window-using-direct2d