#include <iostream>
#include <fstream>
#include <cstring>
#include <cstdlib>
using namespace std;

class Image_pgm {
  int w;
  int h;
  int *content;
public:
  Image_pgm();
  Image_pgm(int, int);
  ~Image_pgm();

  int width() { return w; }
  int height() { return h; }
  int p_read(const char *);
  int p_write(const char *);
  int read_v(int y, int x, unsigned char *c) {
    if (x >= 0 && x < w && y >= 0 && y < h) {
      *c = content[y * this->w + x];
      return 0;
    } else
      return 1;
  }
  int write_v(int y, int x, unsigned char c) {
    if (x >= 0 && x < w && y >= 0 && y < h) {
      content[y * this->w + x] = c;
      return 0;
    } else
      return 1;
  }
};

Image_pgm::Image_pgm() {
  w = h = 0;
  content = 0;
}

Image_pgm::Image_pgm(int w, int h) {
  this->w = w;
  this->h = h;
  this->content = new int[w * h];
}

Image_pgm::~Image_pgm() {
  delete [] content;
}

const int cbuffsize = 1024;
int Image_pgm::p_read(const char *path) {
  ifstream f;
  f.open(path);
  if (!f) {
    cerr << "cannot open the file: " << path << '.' << endl;
    return -1;
  }
  char *p, *p1, *p2, cbuff[cbuffsize];
  int count = 0, max = 255;
  int y = 0;
  f.getline(cbuff, cbuffsize);
  if (strstr(cbuff, "P2") != cbuff) {
    cerr << "cannot find pgm header." << endl;
    return -1;
  }
  while (f.getline(cbuff, cbuffsize)) {
    if (cbuff[0] == '#')
      continue;
    count++;
    if (count == 1) {
      if ((p1 = strtok(cbuff, " ,")) == 0) goto error_handler;
      if ((p2 = strtok(cbuff, " ,")) == 0) goto error_handler;
      this->w = atoi(p1);
      this->h = atoi(p2);
      this->content = new int[this->w * this->h];
    } else if (count == 2) {
      if ((p1 = strtok(cbuff, " ,")) == 0) goto error_handler;
      max = atoi(p1);
    } else {
      for (int i = 0; i < this->w; i++) {
        content[y * this->w + i] = (int)((double)atoi(strtok((i == 0) ? cbuff : 0, " ,")) / max * 255.0);
      }
      y++;
      if (y > h) goto error_handler;
    }
  }
  f.close();
  return 0;
error_handler:
  cerr << "bad format." << endl;
  f.close();
  return -1;
}

int Image_pgm::p_write(const char *path) {
  ofstream f(path);
  if (!f) {
    cerr << "cannot open the file: " << path << endl;
    return -1;
  }
  f << "P2" << endl;
  f << w << " " << h << endl;
  for (int y = 0; y < this->h; y++) {
    for (int x = 0; x < this->w; x++) {
      f << content[y * this->w + x];
      f << " ";
    }
    f << endl;
  }
  return 0;
}

int main() {
  Image_pgm sample1;
  sample1.p_read("a.pgm");
  int wid, hei;
  wid = sample1.width();
  hei = sample1.height();
  Image_pgm sample2(wid, hei);

  for(int i = 0; i < hei; i++) {
    for(int j = 0; j < wid; j++) {
      unsigned char value;
      sample1.read_v(i, j, &value);
      sample2.write_v(i, j, value);
    }
  }
  sample2.p_write("b.pgm");
  return 0;
}
/* end */

cc1plus: warnings being treated as errors
In function 'int main()':
Line 124: warning: 'value' may be used uninitialized in this function