1 | /* |
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2 | * libee ASCII-Art library |
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3 | * Copyright (c) 2002, 2003 Sam Hocevar <sam@zoy.org> |
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4 | * All Rights Reserved |
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5 | * |
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6 | * $Id: conic.c 132 2003-11-10 18:21:36Z sam $ |
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7 | * |
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8 | * This program is free software; you can redistribute it and/or modify |
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9 | * it under the terms of the GNU General Public License as published by |
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10 | * the Free Software Foundation; either version 2 of the License, or |
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11 | * (at your option) any later version. |
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12 | * |
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13 | * This program is distributed in the hope that it will be useful, |
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14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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16 | * GNU General Public License for more details. |
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17 | * |
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18 | * You should have received a copy of the GNU General Public License |
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19 | * along with this program; if not, write to the Free Software |
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20 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. |
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21 | */ |
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22 | |
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23 | #include "config.h" |
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24 | |
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25 | #include <stdlib.h> |
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26 | |
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27 | #include "ee.h" |
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28 | |
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29 | void ee_draw_circle(int x, int y, int r, char c) |
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30 | { |
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31 | int test, dx, dy; |
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32 | |
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33 | /* Optimized Bresenham. Kick ass. */ |
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34 | for(test = 0, dx = 0, dy = r ; dx <= dy ; dx++) |
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35 | { |
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36 | ee_putcharTO(x + dx, y + dy / 2, c); |
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37 | ee_putcharTO(x - dx, y + dy / 2, c); |
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38 | ee_putcharTO(x + dx, y - dy / 2, c); |
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39 | ee_putcharTO(x - dx, y - dy / 2, c); |
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40 | |
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41 | ee_putcharTO(x + dy, y + dx / 2, c); |
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42 | ee_putcharTO(x - dy, y + dx / 2, c); |
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43 | ee_putcharTO(x + dy, y - dx / 2, c); |
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44 | ee_putcharTO(x - dy, y - dx / 2, c); |
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45 | |
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46 | test += test > 0 ? dx - dy-- : dx; |
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47 | } |
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48 | } |
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49 | |
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50 | static void ellipsepoints(int xo, int yo, int x, int y, char c) |
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51 | { |
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52 | ee_putcharTO(xo + x, yo + y, c); |
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53 | ee_putcharTO(xo - x, yo + y, c); |
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54 | ee_putcharTO(xo + x, yo - y, c); |
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55 | ee_putcharTO(xo - x, yo - y, c); |
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56 | } |
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57 | |
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58 | void ee_draw_ellipse(int xo, int yo, int a, int b, char c) |
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59 | { |
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60 | int d2; |
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61 | int x = 0; |
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62 | int y = b; |
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63 | int d1 = b*b - (a*a*b) + (a*a/4); |
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64 | |
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65 | ellipsepoints(xo, yo, x, y, c); |
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66 | |
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67 | while( a*a*y - a*a/2 > b*b*(x+1)) |
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68 | { |
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69 | if(d1 < 0) |
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70 | { |
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71 | d1 += b*b*(2*x+1); /* XXX: "Computer Graphics" has + 3 here. */ |
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72 | } |
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73 | else |
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74 | { |
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75 | d1 += b*b*(2*x*1) + a*a*(-2*y+2); |
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76 | y--; |
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77 | } |
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78 | x++; |
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79 | ellipsepoints(xo, yo, x, y, c); |
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80 | } |
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81 | |
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82 | d2 = b*b*(x+0.5)*(x+0.5) + a*a*(y-1)*(y-1) - a*a*b*b; |
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83 | while(y > 0) |
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84 | { |
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85 | if(d2 < 0) |
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86 | { |
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87 | d2 += b*b*(2*x+2) + a*a*(-2*y+3); |
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88 | x++; |
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89 | } |
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90 | else |
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91 | { |
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92 | d2 += a*a*(-2*y+3); |
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93 | } |
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94 | |
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95 | y--; |
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96 | ellipsepoints(xo, yo, x, y, c); |
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97 | } |
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98 | } |
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99 | |
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