Practical Algorithms for Image Analysis/Practical Algorithms for Image Analysis.iso/CH_2.2/HISTEX/HISTEX.C

C/C++ Source or Header | 1999-09-11 | 5.4 KB | 190 lines

/*
 * histstats.c
 *
 * Practical Algorithms for Image Analysis
 *
 * Copyright (c) 1997, 1998, 1999 MLMSoftwareGroup, LLC
 */

/* HISTEX: program performs histogram expansion upon a b/w image - removing
 *       the tails of the probability density function and expanding that
 *         function to the entire range, where <hiValue> is the max intensity
 *              usage: histex inimg outimg [-p PCT_KEEP] [-m MAXVAL] [-L]
 *
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <tiffimage.h>          /* tiff info on images */
#include <images.h>
extern void print_sos_lic ();

#define NBINS 256               /* no. of histogram bins */
#define PCT_KEEP 98.0           /* percentage of histogram to keep */

int usage (short);
int input (int, char **, double *, long *);
int histogram (char *, int, int *);

main (argc, argv)
     int argc;
     char *argv[];
{
  Image *imgI;                  /* I/O image structure */
  unsigned char **image;        /* input/output image */
  double pctKeep;               /* percent of histogram to keep */
  double tail,                  /* percent of histogram tail to remove */
    expand,                     /* factor for histogram expansion */
    value;                      /* pixel value after hist. expansion */
  long nTotal,                  /* total no. of elements in image */
    hiValue,                    /* high intensity value */
    nRemove,                    /* no. pixels to remove in hist. tail */
    sum,                        /* running sum of pixels in tail */
    shift,                      /* shift (down to zero) for hist. exp. */
    top,                        /* top value for expansion */
    i, j;
  int hist[NBINS];              /* image histogram array */

  struct point imgSize;         /* image dimensions */

/* read user parameter values */
  if ((input (argc, argv, &pctKeep, &hiValue)) < 0)
    return (-1);
  tail = (100.0 - pctKeep) / 2.0;

/* open image */
  imgI = ImageIn (argv[1]);
  if (imgI->bps == 8 && imgI->spp == 3) {
    printf ("Got RGB image!!!\nInput image must be Grayscale or B&W!!\n");
    exit (1);
  }
  image = imgI->img;
  imgSize.y = ImageGetHeight (imgI);
  imgSize.x = ImageGetWidth (imgI);
  printf ("image size is %dx%d\n", imgSize.x, imgSize.y);

/* zero histogram array */
  for (i = 0; i < NBINS; i++)
    hist[i] = 0;

/* construct histogram */
  for (j = 0, nTotal = 0; j < imgSize.y; j++) {
    nTotal += imgSize.x;
    histogram (image[j], imgSize.x, hist);
  }
  nRemove = (int) (nTotal * tail / 100.0);

/* find lower tail */
  for (i = 0, sum = 0; i < NBINS; i++) {
    sum += hist[i];
    if (sum >= nRemove)
      break;
  }
  shift = i;

/* find upper tail */
  for (i = NBINS - 1, sum = 0; i > 0; --i) {
    sum += hist[i];
    if (sum >= nRemove)
      break;
  }
  top = i;
  expand = (double) (hiValue) / (double) (top - shift + 1);

  printf ("Tails: %d, %d. Histogram expansion = %5.2f.\n",
          shift, top, expand);

/* do histogram expansion on input data and write output */
  for (j = 0; j < imgSize.y; j++) {
    for (i = 0; i < imgSize.x; i++) {
      value = (((double) image[j][i]) - shift) * expand;
      if (value < 0.0)
        value = 0.0;
      else if (value > hiValue)
        value = hiValue;
      image[j][i] = (unsigned char) value;
    }
  }
  ImageOut (argv[2], imgI);
  return (0);
}

/* USAGE:       function gives instructions on usage of program
 *                    usage: usage (flag)
 *              When flag is 1, the long message is given, 0 gives short.
 */

int
usage (flag)
     short flag;                /* flag =1 for long message; =0 for short message */
{

/* print short usage message or long */
  printf ("USAGE: histex inimg outimg [-p PCT_KEEP] [-m MAXVAL] [-L]\n");
  if (flag == 0)
    return (-1);

  printf ("\nhistex enhances image contrast by performing\n");
  printf ("histogram expansion.\n\n");
  printf ("ARGUMENTS:\n");
  printf ("    inimg: input image filename (TIF)\n");
  printf ("   outimg: output image filename (TIF)\n\n");
  printf ("OPTIONS:\n");
  printf ("  -p PCT_KEEP: percent of histogram to keep. Tails at upper\n");
  printf ("               and lower of histogram are removed equally.\n");
  printf ("               (default = %d%%)\n", (long) PCT_KEEP);
  printf ("  -m MAXVALUE: maximum value of image intensity (if different\n");
  printf ("               than 255), default = %d\n", NBINS - 1);
  printf ("           -L: print Software License for this module\n");

  return (-1);
}


/* INPUT:       function reads input parameters
 *                  usage: input (argc, argv, pctKeep, hiValue)
 */

#define USAGE_EXIT(VALUE) {usage (VALUE); return (-1);}

int
input (argc, argv, pctKeep, hiValue)
     int argc;
     char *argv[];
     double *pctKeep;           /* percentage of histogram to keep */
     long *hiValue;             /* maximum output intensity value */
{
  long n;

  if (argc == 1)
    USAGE_EXIT (1);
  if (argc == 2)
    USAGE_EXIT (0);

  *pctKeep = PCT_KEEP;
  *hiValue = NBINS - 1;

  for (n = 3; n < argc; n++) {
    if (strcmp (argv[n], "-p") == 0) {
      if (++n == argc || argv[n][0] == '-')
        USAGE_EXIT (0);
      *pctKeep = (double) atol (argv[n]);
    }
    else if (strcmp (argv[n], "-m") == 0) {
      if (++n == argc || argv[n][0] == '-')
        USAGE_EXIT (0);
      *hiValue = atol (argv[n]);
    }
    else if (strcmp (argv[n], "-L") == 0) {
      print_sos_lic ();
      exit (0);
    }
    else
      USAGE_EXIT (0);
  }

  return (0);
}