Conversion between COLORREF and D2D1::ColorF

Question

In my windows desktop application development, both GDI+ and Direct2D are being used for drawing rectangles, lines, ellipses, etc. How do I convert from COLORREF (used in GDI+ for the brush) to D2D1::ColorF (used in Direct2D for the brush) and vice-versa?

Code Sample:

In GDI+, in order to fill a rectangle with a specific colour,

PAINTSTRUCT ps;
HDC hdc;

hdc = BeginPaint(hWnd, &ps);
HBRUSH brush;

brush = ::CreateSolidBrush(*pColor);    //COLORREF* pColor;

::FillRect(hdc, &ps.rcPaint, brush);
::DeleteObject((HGDIOBJ) brush);

EndPaint(hWnd, &ps);

In Direct2D, drawing an ellipse with a specific colour,

pRenderTarget->BeginDraw(); 

//type ID2D1SolidColorBrush - alpha value (4th parameter) is omitted
brush->SetColor(D2D1::ColorF(0.5f,0.5f,0.5f));

const D2D1_ELLIPSE circle1 = D2D1::Ellipse(
              D2D1::Point2F(pt1, pt2, 3.0f, 1.0f);

pRenderTarget->DrawEllipse(circle1, brush);

pRenderTarget->EndDraw();

Answer 1

Both are built from three color components: R, G, B.

ColorF::ColorF:

ColorF(FLOAT, FLOAT, FLOAT, FLOAT)(
  FLOAT r,
  FLOAT g,
  FLOAT b,
  FLOAT a = 1.0
);

COLORREF:

To create a COLORREF color value, use the RGB macro. To extract the individual values for the red, green, and blue components of a color value, use the GetRValue, GetGValue, and GetBValue macros, respectively.

COLORREF RGB(
  BYTE byRed,
  BYTE byGreen,
  BYTE byBlue
);

Specifically, you can use GetRValue, GetGValue, and GetBValue macros to obtain individual components from COLORREF and then use them in the ColorF constructor.