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
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
|
/* genmipmap.c - by David Blythe, SGI */
/* Example of how to generate texture mipmap levels with the
accumulation buffer. */
/* Usage example: genmipmap [file.rgb] */
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <GL/glut.h>
#include "texture.h"
static int w = 512, h = 512;
static int pause;
void
reshape(int w, int h)
{
glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, w, 0, h, -1, 1);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
void
init_textures(char *filename)
{
unsigned *buf;
int width, height, components;
if (filename) {
buf = read_texture(filename, &width, &height, &components);
if (buf == NULL) {
fprintf(stderr, "Error: Can't load image file \"%s\".\n",
filename);
exit(1);
} else {
printf("%d x %d texture loaded\n", width, height);
}
} else {
int i, j;
GLubyte *p;
components = 4;
width = height = 512;
buf = (unsigned *) malloc(width * height * sizeof(unsigned));
p = (GLubyte *) buf;
for (j = 0; j < height; j++) {
for (i = 0; i < width; i++) {
if (i & 1)
p[4 * (i + j * width) + 0] = 0xff;
else
p[4 * (i + j * width) + 1] = 0xff;
if (j & 1)
p[4 * (i + j * width) + 2] = 0xff;
}
}
}
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexImage2D(GL_TEXTURE_2D, 0, components, width,
height, 0, GL_RGBA, GL_UNSIGNED_BYTE,
buf);
free(buf);
}
void
init(char *filename)
{
glEnable(GL_TEXTURE_2D);
init_textures(filename);
}
void
draw_rect(int w, int h)
{
glBegin(GL_QUADS);
glTexCoord2f(0, 0);
glVertex2f(0, 0);
glTexCoord2f(1, 0);
glVertex2f(w, 0);
glTexCoord2f(1, 1);
glVertex2f(w, h);
glTexCoord2f(0, 1);
glVertex2f(0, h);
glEnd();
}
void
stop(void)
{
if (pause) {
printf("? ");
fflush(stdout);
getchar();
}
}
void
acfilter(int width, int height)
{
glClear(GL_COLOR_BUFFER_BIT | GL_ACCUM_BUFFER_BIT);
glMatrixMode(GL_TEXTURE);
if (pause) {
draw_rect(width, height);
stop();
glClear(GL_COLOR_BUFFER_BIT);
}
draw_rect(width / 2, height / 2);
stop();
glAccum(GL_ACCUM, 0.25);
glTranslatef(1.0 / width, 0, 0);
draw_rect(width / 2, height / 2);
stop();
glAccum(GL_ACCUM, 0.25);
glLoadIdentity();
glTranslatef(0, 1.0 / height, 0);
draw_rect(width / 2, height / 2);
stop();
glAccum(GL_ACCUM, 0.25);
glLoadIdentity();
glTranslatef(1.0 / width, 1.0 / height, 0);
draw_rect(width / 2, height / 2);
stop();
glAccum(GL_ACCUM, 0.25);
glAccum(GL_RETURN, 1.0);
glMatrixMode(GL_MODELVIEW);
}
void
display(void)
{
glClear(GL_COLOR_BUFFER_BIT);
draw_rect(w, h);
acfilter(w, h);
glFlush();
}
void
help(void)
{
printf("'h' - help\n");
printf("'s' - toggle single step mode\n");
}
/* ARGSUSED1 */
void
key(unsigned char key, int x, int y)
{
switch (key) {
case 'h':
help();
break;
case 's':
pause ^= 1;
break;
case '\033':
exit(0);
break;
default:
glutPostRedisplay();
}
}
int
main(int argc, char *argv[])
{
glutInit(&argc, argv);
glutInitWindowSize(w, h);
glutInitDisplayMode(GLUT_RGBA | GLUT_ACCUM);
(void) glutCreateWindow("genmipmap");
if (argc > 1)
init(argv[1]);
else
init(0);
glutDisplayFunc(display);
glutKeyboardFunc(key);
glutReshapeFunc(reshape);
glutMainLoop();
return 0; /* ANSI C requires main to return int. */
}
|
