GDI+: GdipWarpPath

[José Roca]

The following example creates a GraphicsPath object and adds a closed figure to the path. The code defines a warp transformation by specifying a source rectangle and an array of four destination points. The source rectangle and destination points are passed to the GdipWarpPath function. The code draws the path twice: once before it has been warped and once after it has been warped.

C++

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

   // Create a path.
   PointF points[] ={
      PointF(20.0f, 60.0f),
      PointF(30.0f, 90.0f),
      PointF(15.0f, 110.0f),
      PointF(15.0f, 145.0f),
      PointF(55.0f, 145.0f),
      PointF(55.0f, 110.0f),
      PointF(40.0f, 90.0f),
      PointF(50.0f, 60.0f)};

   GraphicsPath path;
   path.AddLines(points, 8);
   path.CloseFigure();

   // Draw the path before applying a warp transformation.
   Pen bluePen(Color(255, 0, 0, 255));
   graphics.DrawPath(&bluePen, &path);

   // Define a warp transformation, and warp the path.
   RectF srcRect(10.0f, 50.0f, 50.0f, 100.0f);

   PointF destPts[] = {
      PointF(220.0f, 10.0f),
      PointF(280.0f, 10.0f),
      PointF(100.0f, 150.0f),
      PointF(400.0f, 150.0f)};

   path.Warp(destPts, 4, srcRect);

   // Draw the warped path.
   graphics.DrawPath(&bluePen, &path);

   // Draw the source rectangle and the destination polygon.
   Pen blackPen(Color(255, 0, 0, 0));
   graphics.DrawRectangle(&blackPen, srcRect);
   graphics.DrawLine(&blackPen, destPts[0], destPts[1]);
   graphics.DrawLine(&blackPen, destPts[0], destPts[2]);
   graphics.DrawLine(&blackPen, destPts[1], destPts[3]);
   graphics.DrawLine(&blackPen, destPts[2], destPts[3]);
}


PowerBASIC

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SUB GDIP_WarpPath (BYVAL hdc AS DWORD)

   LOCAL hStatus AS LONG
   LOCAL pGraphics AS DWORD
   LOCAL pPath AS DWORD
   LOCAL pBlackPen AS DWORD
   LOCAL pBluePen AS DWORD
   LOCAL srcRect AS RECTF
   DIM   pts(7) AS POINTF
   DIM   destPts(3) AS POINTF

   hStatus = GdipCreateFromHDC(hdc, pGraphics)

   ' // Create a path.
   hStatus = GdipCreatePath(%FillModeAlternate, pPath)

   pts(0).x = 20 : pts(0).y = 60
   pts(1).x = 30 : pts(1).y = 90
   pts(2).x = 15 : pts(2).y = 110
   pts(3).x = 15 : pts(3).y = 145
   pts(4).x = 55 : pts(4).y = 145
   pts(5).x = 55 : pts(5).y = 110
   pts(6).x = 40 : pts(6).y = 90
   pts(7).x = 50 : pts(7).y = 60

   hStatus = GdipAddPathLine2(pPath, pts(0), 8)
   hStatus = GdipClosePathFigure(pPath)

   ' // Draw the path before applying a warp transformation.
   hStatus = GdipCreatePen1(GDIP_ARGB(255, 0, 0, 255), 1, %UnitWorld, pBluePen)
   hStatus = GdipDrawPath(pGraphics, pBluePen, pPath)

   ' // Define a warp transformation, and warp the path.
   srcRect.x = 10 : srcRect.y = 50 : srcRect.Width = 50 : srcRect.Height = 100

   destPts(0).x = 220 : destPts(0).y = 10
   destPts(1).x = 280 : destPts(1).y = 10
   destPts(2).x = 100 : destPts(2).y = 150
   destPts(3).x = 400 : destPts(3).y = 150

   hStatus = GdipWarpPath(pPath, %NULL, destPts(0), 4, srcRect.x, srcRect.y, srcRect.Width, srcRect.Height, %WarpModePerspective, FlatnessDefault)

   ' // Draw the warped path.
   hStatus = GdipDrawPath(pGraphics, pBluePen, pPath)

   ' // Draw the source rectangle and the destination polygon.
   hStatus = GdipCreatePen1(GDIP_ARGB(255, 0, 0, 0), 1, %UnitWorld, pBlackPen)
   hStatus = GdipDrawRectangle(pGraphics, pBlackPen, srcRect.x, srcRect.y, srcRect.Width, srcRect.Height)
   hStatus = GdipDrawLine(pGraphics, pBlackPen, destpts(0).x, destPts(0).y, destPts(1).x, destPts(1).y)
   hStatus = GdipDrawLine(pGraphics, pBlackPen, destpts(0).x, destPts(0).y, destPts(2).x, destPts(2).y)
   hStatus = GdipDrawLine(pGraphics, pBlackPen, destpts(1).x, destPts(1).y, destPts(3).x, destPts(3).y)
   hStatus = GdipDrawLine(pGraphics, pBlackPen, destpts(2).x, destPts(2).y, destPts(3).x, destPts(3).y)

   ' // Cleanup
   IF pBluePen THEN GdipDeletePen(pBluePen)
   IF pBlackPen THEN GdipDeletePen(pBlackPen)
   IF pPath THEN GdipDeletePath(pPath)
   IF pGraphics THEN GdipDeleteGraphics(pGraphics)

END SUB