#include <stdio.h>
#include <stdlib.h>
#include <math.h>

/*
Puzzle I08 -- filled circle
29 Apr 15 --  modified to concentric circles - lrb
*/

void makeCircles( FILE *image, int nrows, int ncols, int minGray, int maxGray, int numCircles )
{
  const int levelInc  = (maxGray-minGray)/numCircles; /* increment for gray level */

  int r, c ;       /* row and col of current pixel */
  int rc, cc ;      /* row and col of center of image */
  int rd, cd ;      /* row and col difference from center */
  double radius, dist ; /* radius of circle, distance from center */

  int rwidth; /* width of ring */
  int w; /* work variable */

  /* calculate center of image, size of radius */
  rc = nrows/2;
  cc = ncols/2;
  if ( nrows<ncols ) radius = nrows/3;
  else               radius = ncols/3;
  rwidth = radius/numCircles;

// radius is radius of biggest circle

  /* write out the pixel data */
  for ( r=0; r<nrows; r++ )
  {
    rd = r - rc;
    for ( c=0; c<ncols; c++ )
    {
      cd   = c - cc;
      dist = sqrt( (double)(rd*rd + cd*cd) );
      w    = (radius-dist)/rwidth;
      if (dist>radius) fputc( maxGray, image );
      else fputc( maxGray-w*levelInc, image );
    }
  }
}

void openImage( char *argv[], FILE **image, int *nrows, int *ncols, int *minGray, int *maxGray, int *numCircles )
{

  /* open the image file for writing */
  if ( (*image = fopen( argv[1], "wb") ) == NULL )
  {
    printf("file %s could not be created\n", argv[1] );
    exit( EXIT_FAILURE );
  }

  *nrows = atoi( argv[2] );
  if ( *nrows < 1 )
  {
    printf("number of rows must be positive\n");
    exit( EXIT_FAILURE );
  }

  *ncols = atoi( argv[3] );
  if ( *ncols < 1 )
  {
    printf("number of columns must be positive\n");
    exit( EXIT_FAILURE );
  }

  *minGray = atoi( argv[4] );
  if ( *minGray < 1 || *minGray > 255 )
  {
    printf("minGray must be > 0 and < 256\n");
    exit( EXIT_FAILURE );
  }

  *maxGray = atoi( argv[5] );
  if ( *maxGray < 1 || *maxGray > 255 )
  {
    printf("maxGray must be > 0 and < 256\n");
    exit( EXIT_FAILURE );
  }

  *numCircles = atoi( argv[6] );
  if ( *numCircles < 1 )
  {
    printf("numCircles must be > 0\n");
    exit( EXIT_FAILURE );
  }
}

/* write out the PGM Header information
|
| The number of gray levels is assumed to be 255.
|
*/

void writeHeader( FILE *image, int nrows, int ncols )
{
  fprintf( image, "P5 ");
  fprintf( image, "# Created by conCircles\n");

  /* width, height, number of gray levels */
  fprintf( image, "%d %d %d ", ncols, nrows, 255 );
}

int main( int argc, char *argv[] )
{
  int nrows, ncols;
  FILE *image;
  int minGray, maxGray, numCircles;

  /* check the command line parameters */
  if ( argc != 7 )
  {
  printf("concircles fileName.pgm nrows ncols minGray maxGray numCircles\n"); return 0; }

  /* Open the image file, get number of rows and columns */
  openImage( argv, &image, &nrows, &ncols, &minGray, &maxGray, &numCircles );

  /* write header information */
  writeHeader( image, nrows, ncols );

  /* Create the Image */
  makeCircles( image, nrows, ncols, minGray, maxGray, numCircles);

  /* close the file */
  fclose ( image );
  return 1;
}