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/*
* Copyright (c) 1993-2003, Silicon Graphics, Inc.
* All Rights Reserved
*
* Permission to use, copy, modify, and distribute this software for any
* purpose and without fee is hereby granted, provided that the above
* copyright notice appear in all copies and that both the copyright
* notice and this permission notice appear in supporting documentation,
* and that the name of Silicon Graphics, Inc. not be used in
* advertising or publicity pertaining to distribution of the software
* without specific, written prior permission.
*
* THE MATERIAL EMBODIED ON THIS SOFTWARE IS PROVIDED TO YOU "AS-IS" AND
* WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED OR OTHERWISE,
* INCLUDING WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY OR
* FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL SILICON
* GRAPHICS, INC. BE LIABLE TO YOU OR ANYONE ELSE FOR ANY DIRECT,
* SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
* OR ANY DAMAGES WHATSOEVER, INCLUDING WITHOUT LIMITATION, LOSS OF
* PROFIT, LOSS OF USE, SAVINGS OR REVENUE, OR THE CLAIMS OF THIRD
* PARTIES, WHETHER OR NOT SILICON GRAPHICS, INC. HAS BEEN ADVISED OF
* THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE POSSESSION, USE
* OR PERFORMANCE OF THIS SOFTWARE.
*
* US Government Users Restricted Rights
* Use, duplication, or disclosure by the Government is subject to
* restrictions set forth in FAR 52.227.19(c)(2) or subparagraph
* (c)(1)(ii) of the Rights in Technical Data and Computer Software
* clause at DFARS 252.227-7013 and/or in similar or successor clauses
* in the FAR or the DOD or NASA FAR Supplement. Unpublished - rights
* reserved under the copyright laws of the United States.
*
* Contractor/manufacturer is:
* Silicon Graphics, Inc.
* 1500 Crittenden Lane
* Mountain View, CA 94043
* United State of America
*
* OpenGL(R) is a registered trademark of Silicon Graphics, Inc.
*/
/*
* histogram.c
* Compute the histogram of the image. This program illustrates the
* use of the glHistogram() function.
*/
#include <GL/glut.h>
#include <assert.h>
#include <stdlib.h>
#include <stdio.h>
#define HISTOGRAM_SIZE 256 /* Must be a power of 2 */
static GLubyte *pixels;
static GLsizei width, height;
static GLuint bswap(GLuint x)
{
const GLuint ui = 1;
const GLubyte *ubp = (const GLubyte *) &ui;
if (*ubp == 1) {
/* we're on little endiang so byteswap x */
GLsizei y = ((x >> 24)
| ((x >> 8) & 0xff00)
| ((x << 8) & 0xff0000)
| ((x << 24) & 0xff000000));
return y;
}
else {
return x;
}
}
static GLubyte*
readImage( const char* filename, GLsizei* width, GLsizei *height )
{
int n;
GLubyte* pixels;
FILE* infile = fopen( filename, "rb" );
if ( !infile ) {
fprintf( stderr, "Unable to open file '%s'\n", filename );
exit(1);
}
fread( width, sizeof( GLsizei ), 1, infile );
fread( height, sizeof( GLsizei ), 1, infile );
*width = bswap(*width);
*height = bswap(*height);
n = 3 * (*width) * (*height);
pixels = (GLubyte *) malloc( n * sizeof( GLubyte ));
if ( !pixels ) {
fprintf( stderr, "Unable to malloc() bytes for pixels\n" );
return NULL;
}
fread( pixels, sizeof( GLubyte ), n, infile );
fclose( infile );
return pixels;
}
static void init(void)
{
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glClearColor(0.0, 0.0, 0.0, 0.0);
glHistogram(GL_HISTOGRAM, HISTOGRAM_SIZE, GL_RGB, GL_FALSE);
glEnable(GL_HISTOGRAM);
}
static void display(void)
{
int i;
GLushort values[HISTOGRAM_SIZE][3];
glClear(GL_COLOR_BUFFER_BIT);
glRasterPos2i(1, 1);
glDrawPixels(width, height, GL_RGB, GL_UNSIGNED_BYTE, pixels);
glGetHistogram(GL_HISTOGRAM, GL_TRUE, GL_RGB, GL_UNSIGNED_SHORT, values);
/* Plot histogram */
glBegin(GL_LINE_STRIP);
glColor3f(1.0, 0.0, 0.0);
for ( i = 0; i < HISTOGRAM_SIZE; i++ )
glVertex2s(i, values[i][0]);
glEnd();
glBegin(GL_LINE_STRIP);
glColor3f(0.0, 1.0, 0.0);
for ( i = 0; i < HISTOGRAM_SIZE; i++ )
glVertex2s(i, values[i][1]);
glEnd();
glBegin(GL_LINE_STRIP);
glColor3f(0.0, 0.0, 1.0);
for ( i = 0; i < HISTOGRAM_SIZE; i++ )
glVertex2s(i, values[i][2]);
glEnd();
glFlush();
}
static void reshape(int w, int h)
{
glViewport(0, 0, (GLsizei) w, (GLsizei) h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, 256, 0, 10000, -1.0, 1.0);
glMatrixMode(GL_MODELVIEW);
}
static void keyboard(unsigned char key, int x, int y)
{
static GLboolean sink = GL_FALSE;
switch (key) {
case 's' :
sink = !sink;
glHistogram(GL_HISTOGRAM, HISTOGRAM_SIZE, GL_RGB, sink);
break;
case 27:
exit(0);
}
glutPostRedisplay();
}
/* Main Loop
* Open window with initial window size, title bar,
* RGBA display mode, and handle input events.
*/
int main(int argc, char** argv)
{
pixels = readImage("leeds.bin", &width, &height);
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize(width, height);
glutInitWindowPosition(100, 100);
glutCreateWindow(argv[0]);
init();
glutReshapeFunc(reshape);
glutKeyboardFunc(keyboard);
glutDisplayFunc(display);
glutMainLoop();
return 0;
}
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