// ------------------------------------------------------------------------
  // This program is complementary material for the book:
  //
  // Frank Nielsen
  //
  // Visual Computing: Geometry, Graphics, and Vision
  //
  // ISBN: 1-58450-427-7
  //
  // Charles River Media, Inc.
  //
  //
  // All programs are available at www.charlesriver.com/visualcomputing/
  //
  // You may use this program for ACADEMIC and PERSONAL purposes ONLY. 
  //
  //
  // The use of this program in a commercial product requires EXPLICITLY
  // written permission from the author. The author is NOT responsible or 
  // liable for damage or loss that may be caused by the use of this program. 
  //
  // Copyright (c) 2005. Frank Nielsen. All rights reserved.
  // ------------------------------------------------------------------------
   
  // ------------------------------------------------------------------------
  // File: zoneplate2.cpp
  // 
  // Description: create a zone plate image to study the aliasing effect of 
  // resampling
  // ------------------------------------------------------------------------
  
  include <stdafx.h>
  
  include <fstream>
  include <math.h>
  
  using namespace std;
  
  void SaveImagePPM(unsigned char * data, int w, int h, char * file);
  
  int _tmain(int argc, _TCHAR* argv[])
  {
  unsigned char * img;
  int x,y,index;
  int w,h;
  float v,X,Y,c=64;
  
  cout<<"Visual Computing: Geometry, Graphics, and Vision (ISBN:1-58450-427-7)"<<endl;
  cout<<"Demo program\n\n"<<endl;
  
  cout<<"Create a zone plate image."<<endl;
  
  w=h=512;
  img=new unsigned char [3*w*h];
  
  for(x=0;x<w;x++)
          for(y=0;y<h;y++)
          {
          index=3*(y*w+x);
  
          X=c*(x-w/2)/(float)w; Y=c*(y-h/2)/(float)h;
  
          v=sin((float)(X*X+Y*Y));
  
          
          img[index]=img[index+1]=img[index+2]=(unsigned char)(127.5*(v+1));
          
  }
  
  SaveImagePPM(img,w,h,"zoneplate2.ppm");
  delete [] img;
  
  char line[256];
  cout<<"Press Return key"<<endl;
  gets(line);
  
          return 0;
  }
  
  // Save a PPM Image
  void SaveImagePPM(unsigned char * data, int w, int h, char * file)
  {
          ofstream OUT(file, ios::binary);
          if (OUT){
      OUT << "P6" << endl << w << ' ' << h << endl << 255 << endl;
          OUT.write((char *)data, 3*w*h);
          OUT.close();}
  }