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random.c

Go to the documentation of this file.

#include        "sadie.h"

#define         NTIMES          12

/*-Copyright Information------------------------------------------------------*/
/* Copyright (c) 1990 by the University of Arizona Digital Image Analysis Lab */
/*----------------------------------------------------------------------------*/
/*-General Information--------------------------------------------------------*/
/*                                                                            */
/*   This function creates an image consisting of random noise. The noise     */
/*   either has a uniform distribution with a range of sigma, or it has a     */
/*   Gaussian distribution with a standard deviation of sigma.                */
/*                                                                            */
/*----------------------------------------------------------------------------*/
/*-Interface Information------------------------------------------------------*/
void
RANDOM (short nlin,             /*  I   Number of lines in the output image.                  */
        short npix,             /*  I   Number of pixels/line in the output image.            */
        short option,           /*  I   Switch, indicating the noise distribution:            */
        /*      UNIFORM    -   Uniform distribution.                  */
        /*      GAUSSIAN   -   Gaussian distribution.                 */
        double sigma,           /*  I   Standard deviation of the noise.                      */
        IMAGE ** out            /*  O   Address of a pointer to the output image.             */
/*----------------------------------------------------------------------------*/
  )
{
  register short j, k, l;
  double noise, factor, bias;
  char msg[SLEN];

  if (TIMES)
    TIMING (T_RANDOM);
  if (NAMES)
    {
      MESSAGE ('I', "");
      MESSAGE ('I', "RANDOM");
      MESSAGE ('I', "");
      sprintf (msg, " Image size: lines:    %d", nlin);
      MESSAGE ('I', msg);
      sprintf (msg, "             pixels:   %d", npix);
      MESSAGE ('I', msg);
      if (option == UNIFORM)
        {
          sprintf (msg, " Uniform distribution, range: %12.4e", sigma);
        }
      else if (option == GAUSSIAN)
        {
          sprintf (msg, " Gaussian distribution, standard deviation: %12.4e",
                   sigma);
        }
      MESSAGE ('I', msg);
      MESSAGE ('I', " ...............");
    }

  /* check input */
  if (nlin <= 0)
    {
      MESSAGE ('E', " Number of lines must be greater than zero.");
      goto the_end;
    }
  else if (npix <= 0)
    {
      MESSAGE ('E', " Number of pixels/line must be greater than zero.");
      goto the_end;
    }
  else if (option != UNIFORM && option != GAUSSIAN)
    {
      MESSAGE ('E', " Option must be one of UNIFORM or GAUSSIAN.");
      goto the_end;
    }
  else if (sigma <= 0.0)
    {
      MESSAGE ('E', " Noise variance must be greater than zero.");
      goto the_end;
    }

  /* create image of appropriate size */
  if (!CHECKIMG (*out))
    GETMEM (1, nlin, npix, out);
  if (!*out)
    goto the_end;

  factor = (double) RAND_MAX;
  if (option == UNIFORM)
    {
      bias = 0.5;
      for (j = 0; j < nlin; j++)
        {
          for (k = 0; k < npix; k++)
            {

              /* convert uniform distribution to range zero to one */
              noise = (double) rand () / factor;

              /* zero mean and scale to sigma */
              (*out)->data[0][j][k] = (PIXEL) (sigma * (noise - bias));
            }
        }
    }
  else                          /* (option == GAUSSIAN) */
    {
      bias = (double) NTIMES / 2.0;
      for (j = 0; j < nlin; j++)
        {
          for (k = 0; k < npix; k++)
            {

              /* convert uniform distribution to gaussian over range zero to one */
              for (noise = 0.0, l = 0; l < NTIMES; l++)
                {
                  noise += (double) rand ();
                }
              noise /= factor;

              /* zero mean and scale to sigma */
              (*out)->data[0][j][k] = (PIXEL) (sigma * (noise - bias));
            }
        }
    }

the_end:
  if (TIMES)
    TIMING (T_EXIT);
}

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