GDI+: GdipMultiplyWorldTransform

[José Roca]

The following example calls the GdipRotateWorldTransform function to fill its world transformation matrix with the elements that represent a 30-degree rotation. Then the code calls the GdipMultiplyWorldTransform function to replace the world transformation matrix (which represents the 30-degree rotation) of the Graphics object with the product of itself and a translation matrix. At that point, the world transformation matrix of the Graphics object represents a composite transformation: first rotate, then translate. Finally, the code calls the GdipDrawEllipse function to draw an ellipse that is rotated and translated.

C++

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VOID Example_MultiplyTransform(HDC hdc
{
   Graphics graphics(hdc);

   Matrix matrix;
   matrix.Translate(150.0f, 100.0f);

   graphics.RotateTransform(30.0f);                         // first rotate
   graphics.MultiplyTransform(&matrix, MatrixOrderAppend);  // then translate

   Pen pen(Color(255, 0, 0, 255));
   graphics.DrawEllipse(&pen, -80, -40, 160, 80);
}


PowerBASIC

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SUB GDIP_MultiplyWorldTransform (BYVAL hdc AS DWORD)

   LOCAL hStatus AS LONG
   LOCAL pGraphics AS DWORD
   LOCAL pPen AS DWORD
   LOCAL pMatrix AS DWORD

   hStatus = GdipCreateFromHDC(hdc, pGraphics)

   hStatus = GdipCreateMatrix(pMatrix)
   hStatus = GdipTranslateMatrix(pMatrix, 150.0!, 100.0!, %MatrixOrderPrepend)

   hStatus = GdipRotateWorldTransform(pGraphics, 30.0!, %MatrixOrderPrepend)
   hStatus = GdipMultiplyWorldTransform(pGraphics, pMatrix, %MatrixOrderAppend)
   hStatus = GdipCreatePen1(GDIP_ARGB(255,0, 0, 255), 1, %UnitPixel, pPen)
   hStatus = GdipDrawEllipse(pGraphics, pPen, -80, -40, 160, 80)

   ' // Cleanup
   IF pMatrix THEN GdipDeleteMatrix(pMatrix)
   IF pPen THEN GdipDeletePen(pPen)
   IF pGraphics THEN GdipDeleteGraphics(pGraphics)

END SUB