1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
|
/*
** Public Domain mode 13h Bresenham line/circle algorithms
** By Brian Dessent
**
** Written for Borland, modified for others by Bob Stout
*/
#include <stdio.h>
#include <stdlib.h>
#include <dos.h>
#include <conio.h>
#include <time.h> /* for randomize */
#ifndef __TURBOC__
#define random(num) (int)(((rand())*(long)(num))/(((long)RAND_MAX)+1))
#define randomize() srand((unsigned)time(NULL)|1)
#else
#endif
#ifndef MK_FP
#define MK_FP(seg,offset) \
((void far *)(((unsigned long)(seg)<<16) | (unsigned)(offset)))
#endif
#define SCREEN_WIDTH 320
#define SCREEN_HEIGTH 200
#define MAX_X (SCREEN_WIDTH-1)
#define MAX_Y (SCREEN_HEIGTH-1)
/* prototypes */
void setmode(int mode);
void plotdot(int x, int y, char c);
void bresenham_line(int x, int y, int x2, int y2, char c);
void bresenham_circle(int xc, int yc, int r, char c);
void main(void);
/* code begins */
/* uses BIOS to set video mode */
void setmode(int mode)
{
union REGS r;
r.x.ax = mode;
int86(0x10, &r, &r);
}
/* plots a dot at (x, y) with color c */
void plotdot(int x, int y, char c)
{
register char far *addr;
if(x < 0 || x > MAX_X || y < 0 || y > MAX_Y)
return;
addr = MK_FP(0xa000, (SCREEN_WIDTH * y) + x);
*addr = c;
}
/* draws a line from (x, y) to (x2, y2) in color c */
void bresenham_line(int x, int y, int x2, int y2, char c)
{
int i, steep = 0, sx, sy, dx, dy, e;
dx = abs(x2 - x);
sx = ((x2 - x) > 0) ? 1 : -1;
dy = abs(y2 - y);
sy = ((y2 - y) > 0) ? 1 : -1;
if(dy > dx)
{
steep = 1;
x ^= y; /* swap x and y */
y ^= x;
x ^= y;
dx ^= dy; /* swap dx and dy */
dy ^= dx;
dx ^= dy;
sx ^= sy; /* swap sx and sy */
sy ^= sx;
sx ^= sy;
}
e = 2 * dy - dx;
for(i = 0;i < dx;i++)
{
if(steep)
plotdot(y, x, c);
else plotdot(x, y, c);
while(e >= 0)
{
y += sy;
e -= 2 * dx;
}
x += sx;
e += 2 * dy;
}
plotdot(x2, y2, c);
}
/* draws a circle at (xc, yc) with radius r in color c
**
** note: the scaling factor of (SCREEN_WIDTH / SCREEN_HEIGTH) is used when
** updating d. This makes round circles. If you want ellipses, you can
** modify that ratio.
*/
void bresenham_circle(int xc, int yc, int r, char c)
{
int x = 0, y = r, d = 2 * (1 - r);
while(y > 0)
{
plotdot(xc + x, yc + y, c);
plotdot(xc + x, yc - y, c);
plotdot(xc - x, yc + y, c);
plotdot(xc - x, yc - y, c);
if(d + y > 0)
{
y -= 1;
d -= (2 * y * SCREEN_WIDTH / SCREEN_HEIGTH) - 1;
}
if(x > d)
{
x += 1;
d += (2 * x) + 1;
}
}
}
/* draws random lines and circles until a key is pressed in mode 13h */
/* (draws in colors 0 - 63 only) */
void main(void)
{
int i=0;
randomize();
setmode(0x13);
while(!kbhit())
{
bresenham_line(random(SCREEN_WIDTH), random(SCREEN_HEIGTH),
random(SCREEN_WIDTH), random(SCREEN_HEIGTH), i = ++i % 64);
bresenham_circle(random(SCREEN_WIDTH), random(SCREEN_HEIGTH),
random(50), i = ++i % 64);
}
getch();
setmode(0x03); /* set to color text mode, clearing screen */
}
|
