GDI+: GdipGetLineBlend

[José Roca]

The following example creates a linear gradient brush, sets its blend, and uses the brush to fill a rectangle. The code then gets the blend. The blend factors and positions can then be inspected or used in some way.

C++

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VOID Example_GetBlend(HDC hdc)
{
   Graphics myGraphics(hdc);

   // Create a linear gradient brush, and set its blend.
   REAL fac[] = {0.0f, 0.4f, 0.6f, 1.0f};
   REAL pos[] = {0.0f, 0.2f, 0.8f, 1.0f};

   LinearGradientBrush linGrBrush(
      Point(0, 0),
      Point(100, 0),
      Color(255, 255, 0, 0),   // red
      Color(255, 0, 0, 255));  // blue

   linGrBrush.SetBlend(fac, pos, 4);

   // Use the linear gradient brush to fill a rectangle.
   myGraphics.FillRectangle(&linGrBrush, 0, 0, 100, 50);

   // Obtain information about the linear gradient brush.
   INT   blendCount;
   REAL* factors = NULL;
   REAL* positions = NULL;

   blendCount = linGrBrush.GetBlendCount();
   factors = new REAL[blendCount];
   positions = new REAL[blendCount];

   linGrBrush.GetBlend(factors, positions, blendCount);

   for(INT j = 0; j < blendCount; ++j)
   {
      // Inspect or use the value in factors[j].
      // Inspect or use the value in positions[j].
   }
}


PowerBASIC

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SUB GDIP_GetLineBlend (BYVAL hdc AS DWORD)

   LOCAL hStatus AS LONG
   LOCAL pGraphics AS DWORD
   LOCAL pLinBrush AS DWORD
   LOCAL colorRed AS DWORD
   LOCAL colorBlue AS DWORD
   LOCAL blendCount AS LONG
   LOCAL pt1 AS POINTF
   LOCAL pt2 AS POINTF
   LOCAL i AS LONG
   DIM   fac(3) AS SINGLE
   DIM   pos(3) AS SINGLE
   DIM   factors(0) AS SINGLE
   DIM   positions(0) AS SINGLE

   hStatus = GdipCreateFromHDC(hdc, pGraphics)

   ' // Create a linear gradient brush, and set its blend.
   fac(0) = 0.0! : fac(1) = 0.4! : fac(2) = 0.6! : fac(3) = 1.0!
   pos(0) = 0.0! : pos(1) = 0.2! : pos(2) = 0.8! : pos(3) = 1.0!

   pt1.x = 0 : pt1.y = 0 : pt2.x = 100 : pt2.y = 0
   colorRed = GDIP_ARGB(255, 255, 0, 0)
   colorBlue = GDIP_ARGB(255, 0, 0, 255)
   hStatus = GdipCreateLineBrush(pt1, pt2, colorRed, colorBlue, %WrapModeTile, pLinBrush)

   hStatus = GdipSetLineBlend(pLinBrush, fac(0), pos(0), 4)

   ' // Use the linear gradient brush to fill a rectangle.
   hStatus = GdipFillRectangle(pGraphics, pLinBrush, 0, 0, 100, 50)

   ' // Obtain information about the linear gradient brush.
   hStatus = GdipGetLineBlendCount(pLinBrush, blendCount)
   IF blendCount THEN
      REDIM factors(blendCount-1)
      REDIM positions(blendCount-1)
      hStatus = GdipGetLineBlend(pLinBrush, factors(0), positions(0), blendCount)
      FOR i = 0 TO blendCount
         OutputDebugString "factor " & FORMAT$(i) & " =" & STR$(factors(i))
         OutputDebugString "position " & FORMAT$(i) & " =" & STR$(positions(i))
      NEXT
   END IF

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

END SUB