algo/FillCircle.algo.h

   1 /*****************************************************************************
   2  * This file is part of gfxprim library.                                     *
   3  *                                                                           *
   4  * Gfxprim is free software; you can redistribute it and/or                  *
   5  * modify it under the terms of the GNU Lesser General Public                *
   6  * License as published by the Free Software Foundation; either              *
   7  * version 2.1 of the License, or (at your option) any later version.        *
   8  *                                                                           *
   9  * Gfxprim is distributed in the hope that it will be useful,                *
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of            *
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU         *
  12  * Lesser General Public License for more details.                           *
  13  *                                                                           *
  14  * You should have received a copy of the GNU Lesser General Public          *
  15  * License along with gfxprim; if not, write to the Free Software            *
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor,                        *
  17  * Boston, MA  02110-1301  USA                                               *
  18  *                                                                           *
  19  * Copyright (C) 2009-2010 Jiri "BlueBear" Dluhos                            *
  20  *                         <jiri.bluebear.dluhos@gmail.com>                  *
  21  *                                                                           *
  22  * Copyright (C) 2009-2010 Cyril Hrubis <metan@ucw.cz>                       *
  23  *                                                                           *
  24  *****************************************************************************/
  25
  26 /*
  27  * A filled circle drawing algorithm.
  28  *
  29  * A filled circle is drawn in the same way as an unfilled one,
  30  * in a top-down, line per line manner, except that we don't need to draw
  31  * four points in each X step. Instead, we just iterate X
  32  * until we accumulate enough Y changes to reach the next line,
  33  * and then draw the full line.
  34  */
  35
  36 /*
  37  * This macro defines a filled circle drawing function.
  38  * Arguments:
  39  *     CONTEXT_T - user-defined type of drawing context (passed to HLINE)
  40  *     PIXVAL_T  - user-defined pixel value type (passed to HLINE)
  41  *     HLINE     - horizontal line drawing function f(context, x0, x1, y, pixval)
  42  *     FN_NAME   - name of the function to be defined
  43  */
  44 #define DEF_FILLCIRCLE_FN(FN_NAME, CONTEXT_T, PIXVAL_T, HLINE) \
  45 void FN_NAME(CONTEXT_T context, int xcenter, int ycenter, \
  46         unsigned int r, PIXVAL_T pixval) \
  47 { \
  48         int x, y, error; \
  49         for (x = 0, error = -r, y = r; y >= 0; y--) { \
  50                 while (error < 0) { \
  51                         error += 2*x + 1; \
  52                         x++; \
  53                 } \
  54                 error += -2*y + 1; \
  55                 HLINE(context, xcenter-x+1, xcenter+x-1, ycenter-y, pixval); \
  56                 HLINE(context, xcenter-x+1, xcenter+x-1, ycenter+y, pixval); \
  57         } \
  58 }