The salt&Pepper and Gaussian Noise generate Code

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#include <iostream.h>
#include <fstream.h>
#include <stdlib.h> /* ANSI C standard library routines */
#include <string.h> /* ANSI standard string routines */
#include <limits.h>
#include <math.h>
#include <stdio.h>
#include "image.h"
//****************************************************
void GrayImage::addSaltandPepperNoise (double percent)
{
 cout << " Adding " << percent <<
 "% salt and pepper noise to the image...";
 srand(1);
 int count = 0;

 double pr = 1.0-percent/100.0;
 for (int i = 0; i < width; ++i)
  for (int j = 0; j < height; ++j)
  {
   // Generate random number between -1.0 and +1.0
   double random = 2.0*(rand()-RAND_MAX/2.0)/RAND_MAX;
   if (random > pr)
   {
    p[i][j] = 255; // Salt noise
    ++count;
   }
   else if (random < -pr)
   {
    p[i][j] = 0; // Pepper noise
    ++count;
   } 
  }
 double actualpercent = 100.0*count/(width*height);
 cout << "done! (" << actualpercent << "%)" << endl;
}

//************************************************

void GrayImage::addGaussianNoise (double mean, double variance)
{
 cout << " Adding Gaussian noise with mean = " << mean << "and variance = "
   << variance << " to the image...";
 cout.flush();
 srand(1);
 #define unit_random() (1.0*rand()/RAND_MAX)
 #define TWO_PI 6.28318530717958647688

 double temp, u1, u2;
 int ix, iy;
 int num = width*height;
 int tempint;

 u1=0.0;
 for(int i = 0; i < num/2; i++)
 {
  while (u1 == 0.0) u1 = unit_random();
  u2 = unit_random();
  temp = sqrt(-2.0*variance*log(u1));
  ix = 2*i/width;
  iy = 2*i%width;
  tempint = p[ix][iy] + (int) (temp * cos(TWO_PI*u2) + mean);
  if (tempint > 255)
   p[ix][iy] = 255;
  else if (tempint < 0)
   p[ix][iy] = 0;
  else
   p[ix][iy] = (unsigned char) tempint;
  ix = (2*i+1)/width;
  iy = (2*i+1)%width;
  tempint = p[ix][iy] + (int) (temp * sin(TWO_PI*u2) + mean);
  if (tempint > 255)
   p[ix][iy] = 255;
  else if (tempint < 0)
   p[ix][iy] = 0;
  else
   p[ix][iy] = (unsigned char) tempint;
  u1 = 0.0;
 }

 u1=0.0;
 if(num & 1) // If num is odd
 {
  while (u1 == 0.0) u1 = unit_random();
  u2 = unit_random();
  temp = sqrt(-2.0*variance*log(u1));
  ix = (num-1)/width;
  iy = (num-1)%width;
  tempint = p[ix][iy] + (int) (temp * cos(TWO_PI*u2) + mean);
  if (tempint > 255)
   p[ix][iy] = 255;
  else if (tempint < 0)
   p[ix][iy] = 0;
  else
   p[ix][iy] = (unsigned char) tempint;
  u1 = 0.0;
 }

 cout << "done!" << endl;
}