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/*!

  \file Draw_Ellipse.c

  \author Mario Palomo 

  \author Jose M. de la Huerga Fernández

  \author Pepe González Mora

  \date 05-2002

  This library is free software; you can redistribute it and/or

  modify it under the terms of the GNU Library General Public

  License as published by the Free Software Foundation; either

  version 2 of the License, or (at your option) any later version.

  This library is distributed in the hope that it will be useful,

  but WITHOUT ANY WARRANTY; without even the implied warranty of

  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

  Library General Public License for more details.

  You should have received a copy of the GNU Library General Public

  License along with this library; if not, write to the Free Foundation,

  Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

*/

#define SDL_DRAW_PUTPIXEL_BPP(A, B, C)  \

*(##A##(##B##(Uint8*)super->pixels + (y0+y)*super->pitch +               \

                                          (x0+x)*SDL_DRAW_BPP)) = ##C##; \

*(##A##(##B##(Uint8*)super->pixels + (y0-y)*super->pitch +               \

                                          (x0+x)*SDL_DRAW_BPP)) = ##C##; \

*(##A##(##B##(Uint8*)super->pixels + (y0+y)*super->pitch +               \

                                          (x0-x)*SDL_DRAW_BPP)) = ##C##; \

*(##A##(##B##(Uint8*)super->pixels + (y0-y)*super->pitch +               \

                                          (x0-x)*SDL_DRAW_BPP)) = ##C##;

#if SDL_DRAW_BPP == 1

#define SDL_DRAW_PUTPIXEL SDL_DRAW_PUTPIXEL_BPP(0+,0+,color)

#elif SDL_DRAW_BPP == 2

#define SDL_DRAW_PUTPIXEL SDL_DRAW_PUTPIXEL_BPP((Uint16*),0+,color)

#elif SDL_DRAW_BPP == 3

#define SDL_DRAW_PUTPIXEL \

  SDL_DRAW_PUTPIXEL_BPP(0+,1+,colorbyte1)   \

  if (SDL_BYTEORDER == SDL_BIG_ENDIAN) {   \

    SDL_DRAW_PUTPIXEL_BPP(0+,0+,colorbyte2)   \

    SDL_DRAW_PUTPIXEL_BPP(0+,2+,colorbyte0) \

  }else{                                   \

    SDL_DRAW_PUTPIXEL_BPP(0+,0+,colorbyte0)   \

    SDL_DRAW_PUTPIXEL_BPP(0+,2+,colorbyte2) \

  }

#elif SDL_DRAW_BPP == 4

#define SDL_DRAW_PUTPIXEL SDL_DRAW_PUTPIXEL_BPP((Uint32*),0+,color)

#endif /*SDL_DRAW_BPP*/

void SDL_DRAWFUNCTION(SDL_Surface *super,

                      Sint16 x0, Sint16 y0,

                      Uint16 Xradius, Uint16 Yradius,

                      Uint32 color)

{

  Sint32 x, y;

  Sint32 Xchange, Ychange;

  Sint32 EllipseError;

  Sint32 TwoASquare, TwoBSquare;

  Sint32 StoppingX, StoppingY;

#if SDL_DRAW_BPP == 3

  Uint8 colorbyte0 = (Uint8) (color & 0xff);

  Uint8 colorbyte1 = (Uint8) ((color >> 8)  & 0xff);

  Uint8 colorbyte2 = (Uint8) ((color >> 16) & 0xff);

#endif

  TwoASquare = 2*Xradius*Xradius;

  TwoBSquare = 2*Yradius*Yradius;

  /*1st set of points*/

  x = Xradius-1;  /*radius zero == draw nothing*/

  y = 0;

  Xchange = Yradius*Yradius*(1-2*Xradius);

  Ychange = Xradius*Xradius;

  EllipseError = 0;

  StoppingX = TwoBSquare*Xradius;

  StoppingY = 0;

  /*Plot four ellipse points by iteration*/

  while (StoppingX > StoppingY) {

    SDL_DRAW_PUTPIXEL

    ++y;

    StoppingY    += TwoASquare;

    EllipseError += Ychange;

    Ychange      += TwoASquare;

    if (( 2*EllipseError + Xchange) > 0) {

      --x;

      StoppingX    -= TwoBSquare;

      EllipseError += Xchange;

      Xchange      += TwoBSquare;

    }

  }/*while*/

  /*2nd set of points*/

  x = 0;

  y = Yradius-1;  /*radius zero == draw nothing*/

  Xchange = Yradius*Yradius;

  Ychange = Xradius*Xradius*(1-2*Yradius);

  EllipseError = 0;

  StoppingX = 0;

  StoppingY = TwoASquare*Yradius;

  /*Plot four ellipse points by iteration*/

  while (StoppingX < StoppingY) {

    SDL_DRAW_PUTPIXEL

    ++x;

    StoppingX    += TwoBSquare;

    EllipseError += Xchange;

    Xchange      += TwoBSquare;

    if ((2*EllipseError + Ychange) > 0) {

      --y;

      StoppingY    -= TwoASquare;

      EllipseError += Ychange;

      Ychange      += TwoASquare;

    }

  }

}/*Draw_Ellipse*/

#undef SDL_DRAW_PUTPIXEL

#undef SDL_DRAW_PUTPIXEL_BPP