Direct2D 旋转篇

微软文档：Transforms

本篇通过官方文档学习，整理出来的demo，初始样本请先创建一个普通的desktop app。

ID2D1SolidColorBrush* m_pOriginalShapeBrush, * m_pFillBrush,* m_pTransformedShapeBrush;
ID2D1StrokeStyle* m_pStrokeStyleDash;

...

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    case WM_COMMAND:
        {
            int wmId = LOWORD(wParam);
            // Parse the menu selections:
            switch (wmId)
            {
            case IDM_ABOUT:
                DialogBox(hInst, MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, About);
                break;
            case IDM_EXIT:
                DestroyWindow(hWnd);
                break;
            default:
                return DefWindowProc(hWnd, message, wParam, lParam);
            }
        }
        break;
    case WM_PAINT:
        {
            Render();
            ValidateRect(hWnd, NULL);
        }
        break;
     ...
}

...

void Render()
{
    RECT rc;
    GetClientRect(hWnd, &rc);

    D2D1_SIZE_U size = D2D1::SizeU(
        rc.right - rc.left,
        rc.bottom - rc.top
    );
    HRESULT hr = l->CreateHwndRenderTarget(
        D2D1::RenderTargetProperties(),
        D2D1::HwndRenderTargetProperties(hWnd, size),
        &m_pRenderTarget
    );

    m_pRenderTarget->BeginDraw();

    m_pRenderTarget->Clear(D2D1::ColorF(D2D1::ColorF::White));
    transform();

    hr = m_pRenderTarget->EndDraw();

    if (FAILED(hr) || hr == D2DERR_RECREATE_TARGET)
    {
        DiscardGraphicsResources();
    }
}

void DiscardGraphicsResources()
{
    SafeRelease(&m_pOriginalShapeBrush);
    SafeRelease(&m_pFillBrush);
    SafeRelease(&m_pTransformedShapeBrush);
}

void transform()
{
    //旋转
    HRESULT hr = m_pRenderTarget->CreateSolidColorBrush(
        D2D1::ColorF(D2D1::ColorF::Black, 1.0F),
        &m_pOriginalShapeBrush);
    if (SUCCEEDED(hr))
    {
        hr = m_pRenderTarget->CreateSolidColorBrush(
            D2D1::ColorF(D2D1::ColorF(0x9ACD32, 1.0f)),
            &m_pFillBrush
        );
    }
    if (SUCCEEDED(hr))
    {
        hr = m_pRenderTarget->CreateSolidColorBrush(
            D2D1::ColorF(D2D1::ColorF::Blue, 1.0f),
            &m_pTransformedShapeBrush
        );
    }
    // Dash array for dashStyle D2D1_DASH_STYLE_CUSTOM
    float dashes[] = { 1.0f, 2.0f, 2.0f, 3.0f, 2.0f, 2.0f };

    // Stroke Style with Dash Style -- Custom
    if (SUCCEEDED(hr))
    {
        hr = l->CreateStrokeStyle(
            D2D1::StrokeStyleProperties(
                D2D1_CAP_STYLE_FLAT,
                D2D1_CAP_STYLE_FLAT,
                D2D1_CAP_STYLE_ROUND,
                D2D1_LINE_JOIN_MITER,
                10.0f,
                D2D1_DASH_STYLE_CUSTOM,
                0.0f),
            dashes,
            ARRAYSIZE(dashes),
            &m_pStrokeStyleDash
        );
    }

    // Create a rectangle.
    D2D1_RECT_F rectangle_1 = D2D1::Rect(438.0f, 301.5f, 498.0f, 361.5f);

    // Draw the rectangle.
    m_pRenderTarget->DrawRectangle(
        rectangle_1,
        m_pOriginalShapeBrush,
        1.0f,
        m_pStrokeStyleDash
    );

    // Apply the rotation transform to the render target.
    //m_pRenderTarget->SetTransform(
    //    D2D1::Matrix3x2F::Rotation(
    //        45.0f,
    //        D2D1::Point2F(468.0f, 331.5f))
    //);

    //// Fill the rectangle.
    //m_pRenderTarget->FillRectangle(rectangle_1, m_pFillBrush);

    //// Draw the transformed rectangle.
    //m_pRenderTarget->DrawRectangle(rectangle_1, m_pTransformedShapeBrush);
/*************************************************************************/
    //缩放
    // Create a rectangle.
    D2D1_RECT_F rectangle_2 = D2D1::Rect(438.0f, 80.5f, 498.0f, 140.5f);

    // Draw the outline of the rectangle.
    m_pRenderTarget->DrawRectangle(
        rectangle_2,
        m_pOriginalShapeBrush,
        1.0f,
        m_pStrokeStyleDash
    );

    //// Apply the scale transform to the render target.
    //m_pRenderTarget->SetTransform(
    //    D2D1::Matrix3x2F::Scale(
    //        D2D1::Size(1.3f, 1.3f),
    //        D2D1::Point2F(438.0f, 80.5f))
    //);
    //// Draw the outline of the rectangle.
    //m_pRenderTarget->DrawRectangle(rectangle_2, m_pTransformedShapeBrush);
/*****************************************************************************/
    //倾斜
     // Create a rectangle.
    D2D1_RECT_F rectangle_3 = D2D1::Rect(126.0f, 301.5f, 186.0f, 361.5f);

    // Draw the outline of the rectangle.
    m_pRenderTarget->DrawRectangle(
        rectangle_3,
        m_pOriginalShapeBrush,
        1.0f,
        m_pStrokeStyleDash
    );

    //// Apply the skew transform to the render target.
    //m_pRenderTarget->SetTransform(
    //    D2D1::Matrix3x2F::Skew(
    //        45.0f,
    //        10.0f,
    //        D2D1::Point2F(126.0f, 301.5f))
    //);

    //// Paint the interior of the rectangle.
    //m_pRenderTarget->FillRectangle(rectangle_3, m_pFillBrush);

    //// Draw the outline of the rectangle.
    //m_pRenderTarget->DrawRectangle(rectangle_3, m_pTransformedShapeBrush);
/***************************************************************************/
    //平移
     // Create a rectangle.
    D2D1_RECT_F rectangle_4 = D2D1::Rect(126.0f, 80.5f, 186.0f, 140.5f);

    // Draw the outline of the rectangle.
    m_pRenderTarget->DrawRectangle(
        rectangle_4,
        m_pOriginalShapeBrush,
        1.0f,
        m_pStrokeStyleDash
    );

    // Apply the translation transform to the render target.
    m_pRenderTarget->SetTransform(D2D1::Matrix3x2F::Translation(20, 10));

    // Paint the interior of the rectangle.
    m_pRenderTarget->FillRectangle(rectangle_4, m_pFillBrush);

    // Draw the outline of the rectangle.
    m_pRenderTarget->DrawRectangle(rectangle_4, m_pTransformedShapeBrush);

}

效果图：

注意： 对一个对象执行多个变换意味着将多个变换组合为一个。即，将每个变换矩阵的输出用作下一个的输入，从而获得所有矩阵变换的累积效果。

假设将两个变换矩阵（旋转和平移）相乘。结果是一个新的矩阵，同时执行旋转和平移功能。因为矩阵乘法不是可交换的，所以乘以平移变换的旋转变换与乘以旋转变换的平移变换是不同的。

这也就是我每应用一个效果后，都会将其注释的原因。

有专门的文档来介绍了这部分：如何将多个变换应用于对象