src/redbook/minmax.c

   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  Unpublished - rights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
  55 static GLubyte  *pixels;
  56 static GLsizei   width, height;
  57
  58
  59 static 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
  77 static GLubyte *
  78 readImage( 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
 116 static 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
 130 static 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
 145 static 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
 154 static 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  */
 166 int 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 }