minmax.c revision 32001f49 
1/*
2 * Copyright (c) 1993-2003, Silicon Graphics, Inc.
3 * All Rights Reserved
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose and without fee is hereby granted, provided that the above
7 * copyright notice appear in all copies and that both the copyright
8 * notice and this permission notice appear in supporting documentation,
9 * and that the name of Silicon Graphics, Inc. not be used in
10 * advertising or publicity pertaining to distribution of the software
11 * without specific, written prior permission.
12 *
13 * THE MATERIAL EMBODIED ON THIS SOFTWARE IS PROVIDED TO YOU "AS-IS" AND
14 * WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED OR OTHERWISE,
15 * INCLUDING WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY OR
16 * FITNESS FOR A PARTICULAR PURPOSE.  IN NO EVENT SHALL SILICON
17 * GRAPHICS, INC.  BE LIABLE TO YOU OR ANYONE ELSE FOR ANY DIRECT,
18 * SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
19 * OR ANY DAMAGES WHATSOEVER, INCLUDING WITHOUT LIMITATION, LOSS OF
20 * PROFIT, LOSS OF USE, SAVINGS OR REVENUE, OR THE CLAIMS OF THIRD
21 * PARTIES, WHETHER OR NOT SILICON GRAPHICS, INC.  HAS BEEN ADVISED OF
22 * THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED AND ON ANY THEORY OF
23 * LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE POSSESSION, USE
24 * OR PERFORMANCE OF THIS SOFTWARE.
25 *
26 * US Government Users Restricted Rights
27 * Use, duplication, or disclosure by the Government is subject to
28 * restrictions set forth in FAR 52.227.19(c)(2) or subparagraph
29 * (c)(1)(ii) of the Rights in Technical Data and Computer Software
30 * clause at DFARS 252.227-7013 and/or in similar or successor clauses
31 * in the FAR or the DOD or NASA FAR Supplement.  Unpublished - rights
32 * reserved under the copyright laws of the United States.
33 *
34 * Contractor/manufacturer is:
35 *	Silicon Graphics, Inc.
36 *	1500 Crittenden Lane
37 *	Mountain View, CA  94043
38 *	United State of America
39 *
40 * OpenGL(R) is a registered trademark of Silicon Graphics, Inc.
41 */
42
43/*
44 *  minmax.c
45 *  Determine the minimum and maximum values of a group of pixels.
46 *  This demonstrates use of the glMinmax() call.
47 */
48#include <GL/glew.h>
49#include "glut_wrap.h"
50#include <assert.h>
51#include <stdlib.h>
52#include <stdio.h>
53
54
55static GLubyte  *pixels;
56static GLsizei   width, height;
57
58
59static GLuint bswap(GLuint x)
60{
61   const GLuint ui = 1;
62   const GLubyte *ubp = (const GLubyte *) &ui;
63   if (*ubp == 1) {
64      /* we're on little endiang so byteswap x */
65      GLsizei y =  ((x >> 24)
66                    | ((x >> 8) & 0xff00)
67                    | ((x << 8) & 0xff0000)
68                    | ((x << 24) & 0xff000000));
69      return y;
70   }
71   else {
72      return x;
73   }
74}
75
76
77static GLubyte *
78readImage( const char* filename, GLsizei* width, GLsizei *height )
79{
80    int       n;
81    GLubyte*  pixels;
82    size_t    num_read;
83
84    FILE* infile = fopen( filename, "rb" );
85
86    if ( !infile ) {
87	fprintf( stderr, "Unable to open file '%s'\n", filename );
88	return NULL;
89    }
90
91    num_read = fread( width, sizeof( GLsizei ), 1, infile );
92    assert(num_read == 1);
93    num_read = fread( height, sizeof( GLsizei ), 1, infile );
94    assert(num_read == 1);
95
96    *width = bswap(*width);
97    *height = bswap(*height);
98
99    n = 3 * (*width) * (*height);
100
101    pixels = (GLubyte *) malloc( n * sizeof( GLubyte ));
102    if ( !pixels ) {
103	fprintf( stderr, "Unable to malloc() bytes for pixels\n" );
104	fclose( infile );
105	return NULL;
106    }
107
108    num_read = fread( pixels, sizeof( GLubyte ), n, infile );
109    assert(num_read == n);
110
111    fclose( infile );
112
113    return pixels;
114}
115
116static void init(void)
117{
118   if (!glutExtensionSupported("GL_ARB_imaging")) {
119      fprintf(stderr, "Sorry, this program requires GL_ARB_imaging.\n");
120      exit(1);
121   }
122
123   glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
124   glClearColor(0.0, 0.0, 0.0, 0.0);
125
126   glMinmax(GL_MINMAX, GL_RGB, GL_FALSE);
127   glEnable(GL_MINMAX);
128}
129
130static void display(void)
131{
132   GLubyte  values[6];
133
134   glClear(GL_COLOR_BUFFER_BIT);
135   glRasterPos2i(1, 1);
136   glDrawPixels(width, height, GL_RGB, GL_UNSIGNED_BYTE, pixels);
137   glFlush();
138
139   glGetMinmax(GL_MINMAX, GL_TRUE, GL_RGB, GL_UNSIGNED_BYTE, values);
140   printf(" Red   : min = %d   max = %d\n", values[0], values[3]);
141   printf(" Green : min = %d   max = %d\n", values[1], values[4]);
142   printf(" Blue  : min = %d   max = %d\n", values[2], values[5]);
143}
144
145static void reshape(int w, int h)
146{
147   glViewport(0, 0, (GLsizei) w, (GLsizei) h);
148   glMatrixMode(GL_PROJECTION);
149   glLoadIdentity();
150   glOrtho(0, w, 0, h, -1.0, 1.0);
151   glMatrixMode(GL_MODELVIEW);
152}
153
154static void keyboard(unsigned char key, int x, int y)
155{
156   switch (key) {
157      case 27:
158         exit(0);
159   }
160}
161
162/*  Main Loop
163 *  Open window with initial window size, title bar,
164 *  RGBA display mode, and handle input events.
165 */
166int main(int argc, char** argv)
167{
168   pixels = readImage("leeds.bin", &width, &height);
169
170   glutInit(&argc, argv);
171   glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
172   glutInitWindowSize(width, height);
173   glutInitWindowPosition(100, 100);
174   glutCreateWindow(argv[0]);
175   glewInit();
176   init();
177   glutReshapeFunc(reshape);
178   glutKeyboardFunc(keyboard);
179   glutDisplayFunc(display);
180   glutMainLoop();
181   return 0;
182}
183