PowerBasic Museum 2020-A

The following example creates a Graphics object and sets its compositing mode to CompositingModeSourceOver. The code creates a solid brush based on a color that has an alpha component of 128. The code passes the address of that brush to the GdipFillRectangle function to fill a rectangle with a color that is a half-and-half blend of the brush color and the background color. Then the code sets the compositing mode of the Graphics object to CompositingModeSourceCopy and fills a second rectangle with the same brush. In that second rectangle, the brush color is not blended with the background color.

C++


VOID Example_SetCompositingMode(HDC hdc)
{
   Graphics graphics(hdc);
   
   // Create a SolidBrush object with an alpha-blended color.
   SolidBrush alphaBrush(Color(180, 255, 0, 0));

   // Set the compositing mode to CompositingModeSourceOver,
   // and fill a rectangle.
   graphics.SetCompositingMode(CompositingModeSourceOver);
   graphics.FillRectangle(&alphaBrush, 0, 0, 100, 100);

   // Set the compositing mode to CompositingModeSourceCopy,
   // and fill a rectangle.
   graphics.SetCompositingMode(CompositingModeSourceCopy);
   graphics.FillRectangle(&alphaBrush, 100, 0, 100, 100);
}


PowerBASIC


SUB GDIP_SetCompositingMode (BYVAL hdc AS DWORD)

   LOCAL hStatus AS LONG
   LOCAL pGraphics AS DWORD
   LOCAL pAlphaBrush AS DWORD

   hStatus = GdipCreateFromHDC(hdc, pGraphics)

   ' // Create a SolidBrush object with an alpha-blended color.
   hStatus = GdipCreateSolidFill(GDIP_ARGB(180, 255, 0, 0), pAlphaBrush)

   ' // Set the compositing mode to CompositingModeSourceOver, and fill a rectangle.
   hStatus = GdipSetCompositingMode(pGraphics, %CompositingModeSourceOver)
   hStatus = GdipFillRectangle(pGraphics, pAlphaBrush, 0, 0, 100, 100)

   ' // Set the compositing mode to CompositingModeSourceCopy, and fill a rectangle.
   hStatus = GdipSetCompositingMode(pGraphics, %CompositingModeSourceCopy)
   hStatus = GdipFillRectangle(pGraphics, pAlphaBrush, 100, 0, 100, 100)

   ' // Cleanup
   IF pAlphaBrush THEN GdipDeleteBrush(pAlphaBrush)
   IF pGraphics THEN GdipDeleteGraphics(pGraphics)

END SUB


(http://www.jose.it-berater.org/captures/GdipSetCompositingMode.png)