/*!
\file Draw_Ellipse.c
\author Mario Palomo <mpalomo@ihman.com>
\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