GDI+: GdipMultiplyLineTransform

[José Roca]

The following example creates a linear gradient brush and uses it to fill a rectangle. Next, the code sets the brush's transformation matrix, fills a rectangle with the transformed brush, modifies the brush's transformation matrix, and again fills a rectangle with the transformed brush.

C++

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

   Matrix S(2, 0, 0, 1, 0, 0);   // horizontal doubling
   Matrix T(1, 0, 0, 1, 50, 0);  // horizontal translation of 50 units

   LinearGradientBrush linGrBrush(
      Rect(0, 0, 200, 100),
      Color(255, 255, 0, 0),     // red
      Color(255, 0, 0, 255),     // blue
      LinearGradientModeHorizontal);

   // Fill a large area with the gradient brush (no transformation).
   myGraphics.FillRectangle(&linGrBrush, 0, 0, 800, 100);

   // Apply the scaling transformation.
   linGrBrush.SetTransform(&S);

   // Fill a large area with the scaled gradient brush.
   myGraphics.FillRectangle(&linGrBrush, 0, 150, 800, 100);

   // Form a composite transformation: first scale, then translate.
   linGrBrush.MultiplyTransform(&T, MatrixOrderAppend);

   // Fill a large area with the scaled and translated gradient brush.
   myGraphics.FillRectangle(&linGrBrush, 0, 300, 800, 100);
}


PowerBASIC

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SUB GDIP_MultiplyLineTransform (BYVAL hdc AS DWORD)

   LOCAL hStatus AS LONG
   LOCAL pGraphics AS DWORD
   LOCAL pLinBrush AS DWORD
   LOCAL rc AS RECTF
   LOCAL colorRed AS DWORD
   LOCAL colorBlue AS DWORD
   LOCAL S AS DWORD
   LOCAL T AS DWORD

   hStatus = GdipCreateFromHDC(hdc, pGraphics)

   hStatus = GdipCreateMatrix2(2, 0, 0, 1, 0, 0, S)    ' // horizontal doubling
   hStatus = GdipCreateMatrix2(1, 0, 0, 1, 50, 0, T)   ' // horizontal translation of 50 units

   rc.x = 0 : rc.y = 0 : rc.Width = 200 : rc.Height = 100
   colorRed = GDIP_ARGB(255, 255, 0, 0)
   colorBlue = GDIP_ARGB(255, 0, 0, 255)
   hStatus = GdipCreateLineBrushFromRect(rc, colorRed, colorBlue, %LinearGradientModeHorizontal, %WrapModeTile, pLinBrush)

   ' // Fill a large area with the gradient brush (no transformation).
   hStatus = GdipFillRectangle(pGraphics, pLinBrush, 0, 0, 800, 100)

   ' // Apply the scaling transformation.
   hStatus = GdipSetLineTransform(pLinBrush, S)

   ' // Fill a large area with the scaled gradient brush.
   hStatus = GdipFillRectangle(pGraphics, pLinBrush, 0, 150, 800, 100)

   ' // Form a composite transformation: first scale, then translate.
   hStatus = GdipMultiplyLineTransform(pLinBrush, T, %MatrixOrderAppend)

   ' // Fill a large area with the scaled and translated gradient brush.
   hStatus = GdipFillRectangle(pGraphics, pLinBrush, 0, 300, 800, 100)

   ' // Cleanup
   IF S THEN GdipDeleteMatrix(S)
   IF T THEN GdipDeleteMatrix(T)
   IF pLinBrush THEN GdipDeleteBrush(pLinBrush)
   IF pGraphics THEN GdipDeleteGraphics(pGraphics)

END SUB