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histogram.c
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histogram.c
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/* -*- mode:C; indent-tabs-mode:nil; tab-width:8; c-basic-offset:8; -*-
*
* Histogram functions
*
* Author: William Jon McCann
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
* $Id: histogram.c,v 1.7 2004/04/30 18:28:12 mccannwj Exp $
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <pwd.h>
#include <errno.h>
#include "getopt.h"
#include <signal.h>
#include <ctype.h>
#include <math.h>
#include <float.h>
#ifdef STDC_HEADERS
#include <stdlib.h>
#else /* Not STDC_HEADERS */
extern void exit ();
extern char *malloc ();
#endif /* STDC_HEADERS */
#include "fitscut.h"
#include "histogram.h"
#ifdef DMALLOC
#include <dmalloc.h>
#define DMALLOC_FUNC_CHECK 1
#endif
/*
** returns a (length+1) bin histogram with one bin for objects below dmin, length-1 bins for objects
** between dmin and dmax, and one bin for objects above dmax
**/
float *
compute_histogram (float *arrayp, int length, double dmin, double dmax, long npix, float bad_data_value, long *pixcount, float *inmin, float *inmax)
{
float *hist;
double binsize;
long i, ind;
float value;
float fmin, fmax;
long lpixcount;
/* allocate histogram */
hist = (float*) malloc (sizeof (float) * (length + 1));
/* Initialize histogram */
for (i = 0; i <= length; i++)
hist[i] = 0;
/* Build histogram */
fitscut_message (3, "\tbuilding histogram...\n");
binsize = (dmax - dmin) / (length - 1);
fitscut_message (4, "\tdmax: %lf dmin: %lf length: %d binsize: %lf npix: %ld...\n",
dmax, dmin, length, binsize, npix);
lpixcount = 0;
fmin = FLT_MAX;
fmax = -FLT_MAX;
for (i = 0; i < npix; i++) {
value = arrayp[i];
/* exclude blanked values */
if (finite(value) && (value != bad_data_value)) {
if (value < dmin) {
ind = 0;
} else if (value > dmax) {
ind = length-1;
} else {
ind = ceil ((value-dmin) / binsize);
if (value > fmax) fmax = value;
if (value < fmin) fmin = value;
}
hist[ind] += 1.0;
lpixcount++;
}
}
/* return total number of pixels excluding blanks in pixcount */
*pixcount = lpixcount;
/* return min/max range for pixels within histogram bounds to allow refinement */
if (fmin > fmax) {
/* no pixels in bounds */
*inmin = 0.5*(dmin+dmax);
*inmax = *inmin;
} else {
*inmin = fmin;
*inmax = fmax;
}
return (hist);
}
unsigned char *
eq_histogram (float *hist, int length, long npix)
{
int i, j;
int *part;
unsigned char *lut;
double pixels_per_value;
double desired;
double sum, dif;
/* allocate partition */
part = (int*) malloc (sizeof (int) * 257);
/* allocate look up table */
lut = (unsigned char*) malloc (sizeof (unsigned char) * (length + 1));
/* Find partition points */
pixels_per_value = ((double) npix) / 256.0;
/* First and last points in partition */
part[0] = 0;
part[256] = 256;
/* Find intermediate points */
j = 0;
sum = hist[0] + hist[1];
for (i = 1; i < 256; i++) {
desired = i * pixels_per_value;
while (sum <= desired) {
j++;
sum += hist[j+1];
}
/* Nearest sum */
dif = sum - hist[j];
if ((sum - desired) > (dif / 2.0))
part[i] = j;
else
part[i] = j + 1;
}
/* Create equalization LUT */
for (j = 0; j < length; j++) {
i = 0;
while (part[i + 1] <= j)
i++;
if (i > 255)
i = 255;
lut[j] = i;
}
free (part);
return (lut);
}