L_CurveToBezier

#include "l_bitmap.h"

L_LTDIS_API L_INT L_CurveToBezier(pCurve, pOutPointCount, pOutPoint)

Converts a curve (defined by an array of points that the curve passes through) to an array of Bezier points. The resulting array can be used to with the Windows C DLLs PolyBezier and PolyBezierTo.

Returns

Comments

This function is used to convert a standard curve to an array of Bezier control points. A LEAD standard curve (CURVE_STANDARD) is defined by the CURVE structure, and one of the fields is an array of POINT structures. The standard curve passes through all of the points in the array, and is continuous at each point. This function can be used to draw this curve by converting it to an array of Bezier points, and using the Windows C DLL PolyBezier (or PolyBezierTo) to draw the equivalent Bezier.

To use this function, declare a variable of type CURVE, and fill in the appropriate fields. For this function, all fields of the CURVE structure are required EXCEPT uFillMode, which is ignored. For more information, refer to the CURVE structure.

The pOutPoint must point to an array of POINT structures that is large enough to hold the Bezier control points. At most, the resulting array must hold (3n + 1) entries, where n is the number of points in the CURVE_STANDARD curve. If this function is called with pOutPoint set to NULL, pOutPointCount will be updated with the required number of entries in the pOutPoint array.

Required DLLs and Libraries

Platforms

Windows 2000 / XP/Vista.

See Also

Example

This sample draws a smooth closed curve on hDC that goes through five points

L_INT CurveToBezierExample(HDC hDC)
{
   L_INT    nRet;
   CURVE    Curve;
   POINT    points[5];
   L_INT    nOutPointCount;
   LPPOINT  pOutPoints;
   HPEN     hPen, hPrevPen;
   L_INT    nPrevROP2;

   //Define the points of the curve
   points[0].x = 130;
   points[0].y = 130;

   points[1].x = 130;
   points[1].y = 300;

   points[2].x = 230;
   points[2].y = 230;

   points[3].x = 175;
   points[3].y = 175;

   points[4].x = 230;
   points[4].y = 130;

   Curve.uStructSize = sizeof(CURVE); 
   Curve.nType       = CURVE_STANDARD;
   Curve.nPointCount = 5;
   Curve.pPoints     = points;
   Curve.uFillMode   = L_POLY_WINDING;  //This member is ignored
   Curve.dTension    = 0.5; 
   Curve.nClose      = CURVE_CLOSE;
   Curve.nReserved   = 0;

   //Determined the number of required points
   nRet = L_CurveToBezier(&Curve, &nOutPointCount, NULL);
   if (nRet != SUCCESS)
      return nRet;

   pOutPoints = (LPPOINT)malloc( sizeof(POINT) * nOutPointCount);

   if (pOutPoints == NULL)
      return FAILURE;

   nRet = L_CurveToBezier(&Curve, &nOutPointCount, pOutPoints);
   if (nRet != SUCCESS)
   {
      free(pOutPoints);
      return nRet;
   }

   //Create a pen
    hPen = CreatePen(PS_SOLID, 1,RGB(255,255,255));
    hPrevPen = (HPEN)SelectObject(hDC, hPen);
    nPrevROP2 = SetROP2(hDC, R2_XORPEN);

   //Draw the curve that goes through the original five points
   nRet = PolyBezier(hDC, pOutPoints, nOutPointCount);

   //Restore the hDC
   SetROP2(hDC, nPrevROP2);
   SelectObject(hDC, hPrevPen);
   DeleteObject(hPen);

   free(pOutPoints);
   return SUCCESS;
}