How to Transform a Geometry

To transform a geometry, you can either apply the transform to the render target by calling SetTransform or apply the transform to the geometry by calling CreateTransformedGeometry. Although both approaches transform a geometry, they have some fundamental differences. CreateTransformedGeometry affects the fill, but does not affect the stroke width. Further, CreateTransformedGeometry transforms the geometry alone without impacting other shapes on the render target, whereas SetTransform applies the transform to all shapes on the render target.

This how-to topic describes how to transform a geometry by calling CreateTransformedGeometry.

To transform a geometry

1. Declare an ID2D1TransformedGeometry variable.
2. Call the CreateTransformedGeometry method to create a transformed geometry.

The following code shows how to create an hour glass, transform the hour glass, and draw the original and resulting hour glasses.

// Create a path geometry.
if (SUCCEEDED(hr))
{
    hr = m_pD2DFactory->CreatePathGeometry(&m_pPathGeometry);

    if (SUCCEEDED(hr))
    {
        // Write to the path geometry using the geometry sink.
        hr = m_pPathGeometry->Open(&pSink);

        if (SUCCEEDED(hr))
        {
            pSink->BeginFigure(
                D2D1::Point2F(0, 0),
                D2D1_FIGURE_BEGIN_FILLED
                );

            pSink->AddLine(D2D1::Point2F(200, 0));

            pSink->AddBezier(
                D2D1::BezierSegment(
                    D2D1::Point2F(150, 50),
                    D2D1::Point2F(150, 150),
                    D2D1::Point2F(200, 200))
                );

            pSink->AddLine(D2D1::Point2F(0, 200));

            pSink->AddBezier(
                D2D1::BezierSegment(
                    D2D1::Point2F(50, 150),
                    D2D1::Point2F(50, 50),
                    D2D1::Point2F(0, 0))
                );

            pSink->EndFigure(D2D1_FIGURE_END_CLOSED);

            hr = pSink->Close();
        }
        SafeRelease(&pSink);
    }
}

if (SUCCEEDED(hr))
{
    // Create a transformed geometry which is tilted at an angle to the previous geometry
    hr = m_pD2DFactory->CreateTransformedGeometry(
        m_pPathGeometry,
        D2D1::Matrix3x2F::Rotation(
            45.f,
            D2D1::Point2F(100, 100)),
        &m_pTransformedGeometry
        );
}