如何使用D2D和CD2DEllipse类在C++ MFC上绘制椭圆

#include <d2d1.h>

class CMyMFCWindow : public CWnd
{
private:
    ID2D1Factory* m_pD2DFactory;
    ID2D1HwndRenderTarget* m_pRenderTarget;

    void CreateD2DResources();
    void ReleaseD2DResources();
    void DrawEllipse();
    
protected:
    afx_msg void OnPaint();
    DECLARE_MESSAGE_MAP()
};

CMyMFCWindow::CMyMFCWindow()
{
    m_pD2DFactory = nullptr;
    m_pRenderTarget = nullptr;
}

CMyMFCWindow::~CMyMFCWindow()
{
    ReleaseD2DResources();
}

void CMyMFCWindow::CreateD2DResources()
{
    if (m_pRenderTarget == nullptr)
    {
        // 创建D2D工厂
        D2D1CreateFactory(D2D1_FACTORY_TYPE_SINGLE_THREADED, &m_pD2DFactory);

        // 获取窗口的设备上下文
        CClientDC dc(this);
        CDC* pDC = CDC::FromHandle(dc.m_hDC);
        HDC hDC = pDC->GetSafeHdc();

        // 创建D2D渲染目标
        D2D1_RENDER_TARGET_PROPERTIES renderTargetProperties = D2D1::RenderTargetProperties(
            D2D1_RENDER_TARGET_TYPE_DEFAULT,
            D2D1::PixelFormat(DXGI_FORMAT_UNKNOWN, D2D1_ALPHA_MODE_PREMULTIPLIED),
            0,
            0,
            D2D1_RENDER_TARGET_USAGE_NONE,
            D2D1_FEATURE_LEVEL_DEFAULT
        );
        m_pD2DFactory->CreateHwndRenderTarget(
            renderTargetProperties,
            D2D1::HwndRenderTargetProperties(hDC, D2D1::SizeU(0, 0)),
            &m_pRenderTarget
        );
    }
}

void CMyMFCWindow::ReleaseD2DResources()
{
    if (m_pRenderTarget != nullptr)
    {
        m_pRenderTarget->Release();
        m_pRenderTarget = nullptr;
    }

    if (m_pD2DFactory != nullptr)
    {
        m_pD2DFactory->Release();
        m_pD2DFactory = nullptr;
    }
}

void CMyMFCWindow::DrawEllipse()
{
    if (m_pRenderTarget != nullptr)
    {
        // 清空渲染目标
        m_pRenderTarget->BeginDraw();
        m_pRenderTarget->Clear(D2D1::ColorF(D2D1::ColorF::White));

        // 创建椭圆
        CD2DEllipse ellipse(D2D1::Ellipse(D2D1::Point2F(100, 100), 50, 30));

        // 绘制椭圆
        m_pRenderTarget->DrawEllipse(ellipse, m_pD2DFactory->CreateSolidColorBrush(D2D1::ColorF(D2D1::ColorF::Red)));

        // 结束绘制
        m_pRenderTarget->EndDraw();
    }
}

void CMyMFCWindow::OnPaint()
{
    CPaintDC dc(this);
    CreateD2DResources();
    DrawEllipse();
}

BEGIN_MESSAGE_MAP(CMyMFCWindow, CWnd)
    ON_WM_PAINT()
END_MESSAGE_MAP()