source: ttyvaders/trunk/libee/conic.c @ 132

Last change on this file since 132 was 132, checked in by Sam Hocevar, 17 years ago
  • libee/conic.c: + ee_draw_ellipse().
  • Property svn:keywords set to Id
File size: 2.5 KB
Line 
1/*
2 *   libee         ASCII-Art library
3 *   Copyright (c) 2002, 2003 Sam Hocevar <sam@zoy.org>
4 *                 All Rights Reserved
5 *
6 *   $Id: conic.c 132 2003-11-10 18:21:36Z sam $
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
23#include "config.h"
24
25#include <stdlib.h>
26
27#include "ee.h"
28
29void ee_draw_circle(int x, int y, int r, char c)
30{
31    int test, dx, dy;
32
33    /* Optimized Bresenham. Kick ass. */
34    for(test = 0, dx = 0, dy = r ; dx <= dy ; dx++)
35    {
36        ee_putcharTO(x + dx, y + dy / 2, c);
37        ee_putcharTO(x - dx, y + dy / 2, c);
38        ee_putcharTO(x + dx, y - dy / 2, c);
39        ee_putcharTO(x - dx, y - dy / 2, c);
40
41        ee_putcharTO(x + dy, y + dx / 2, c);
42        ee_putcharTO(x - dy, y + dx / 2, c);
43        ee_putcharTO(x + dy, y - dx / 2, c);
44        ee_putcharTO(x - dy, y - dx / 2, c);
45
46        test += test > 0 ? dx - dy-- : dx;
47    }
48}
49
50static void ellipsepoints(int xo, int yo, int x, int y, char c)
51{
52    ee_putcharTO(xo + x, yo + y, c);
53    ee_putcharTO(xo - x, yo + y, c);
54    ee_putcharTO(xo + x, yo - y, c);
55    ee_putcharTO(xo - x, yo - y, c);
56}
57
58void ee_draw_ellipse(int xo, int yo, int a, int b, char c)
59{
60    int d2;
61    int x = 0;
62    int y = b;
63    int d1 = b*b - (a*a*b) + (a*a/4);
64
65    ellipsepoints(xo, yo, x, y, c);
66
67    while( a*a*y - a*a/2 > b*b*(x+1))
68    {
69        if(d1 < 0)
70        {
71            d1 += b*b*(2*x+1); /* XXX: "Computer Graphics" has + 3 here. */
72        }
73        else
74        {
75            d1 += b*b*(2*x*1) + a*a*(-2*y+2);
76            y--;
77        }
78        x++;
79        ellipsepoints(xo, yo, x, y, c);
80    }
81
82    d2 = b*b*(x+0.5)*(x+0.5) + a*a*(y-1)*(y-1) - a*a*b*b;
83    while(y > 0)
84    {
85        if(d2 < 0)
86        {
87            d2 += b*b*(2*x+2) + a*a*(-2*y+3);
88            x++;
89        }
90        else
91        {
92            d2 += a*a*(-2*y+3);
93        }
94
95        y--;
96        ellipsepoints(xo, yo, x, y, c);
97    }
98}
99
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