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  1. /*
  2. * libee ASCII-Art library
  3. * Copyright (c) 2002, 2003 Sam Hocevar <sam@zoy.org>
  4. * All Rights Reserved
  5. *
  6. * $Id$
  7. *
  8. * This program is free software; you can redistribute it and/or modify
  9. * it under the terms of the GNU General Public License as published by
  10. * the Free Software Foundation; either version 2 of the License, or
  11. * (at your option) any later version.
  12. *
  13. * This program is distributed in the hope that it will be useful,
  14. * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15. * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16. * GNU General Public License for more details.
  17. *
  18. * You should have received a copy of the GNU General Public License
  19. * along with this program; if not, write to the Free Software
  20. * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21. */
  22. #include "config.h"
  23. #include <stdlib.h>
  24. #include "ee.h"
  25. static void ellipsepoints(int, int, int, int, char);
  26. void ee_draw_circle(int x, int y, int r, char c)
  27. {
  28. int test, dx, dy;
  29. /* Optimized Bresenham. Kick ass. */
  30. for(test = 0, dx = 0, dy = r ; dx <= dy ; dx++)
  31. {
  32. ellipsepoints(x, y, dx, dy, c);
  33. ellipsepoints(x, y, dy, dx, c);
  34. test += test > 0 ? dx - dy-- : dx;
  35. }
  36. }
  37. void ee_draw_ellipse(int xo, int yo, int a, int b, char c)
  38. {
  39. int d2;
  40. int x = 0;
  41. int y = b;
  42. int d1 = b*b - (a*a*b) + (a*a/4);
  43. ellipsepoints(xo, yo, x, y, c);
  44. while( a*a*y - a*a/2 > b*b*(x+1))
  45. {
  46. if(d1 < 0)
  47. {
  48. d1 += b*b*(2*x+1); /* XXX: "Computer Graphics" has + 3 here. */
  49. }
  50. else
  51. {
  52. d1 += b*b*(2*x*1) + a*a*(-2*y+2);
  53. y--;
  54. }
  55. x++;
  56. ellipsepoints(xo, yo, x, y, c);
  57. }
  58. d2 = b*b*(x+0.5)*(x+0.5) + a*a*(y-1)*(y-1) - a*a*b*b;
  59. while(y > 0)
  60. {
  61. if(d2 < 0)
  62. {
  63. d2 += b*b*(2*x+2) + a*a*(-2*y+3);
  64. x++;
  65. }
  66. else
  67. {
  68. d2 += a*a*(-2*y+3);
  69. }
  70. y--;
  71. ellipsepoints(xo, yo, x, y, c);
  72. }
  73. }
  74. static void ellipsepoints(int xo, int yo, int x, int y, char c)
  75. {
  76. ee_putcharTO(xo + x, yo + y, c);
  77. ee_putcharTO(xo - x, yo + y, c);
  78. ee_putcharTO(xo + x, yo - y, c);
  79. ee_putcharTO(xo - x, yo - y, c);
  80. }