/*
 * usage:  autocolor <inputfile>
 *
 * inputfile is "-" to read from stdin.  result (a PPM) is produced on stdout.
 * maps input gray levels to arbitrary unique colors.  leaves black pixels
 * unchanged.
 */

#include <iostream>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <string.h>
#include <math.h>


using namespace std;

void hsv_to_rgb( double h, double s, double v,
		 unsigned char* r, unsigned char* g, unsigned char* b );
unsigned char* read_pgm( char* filename, int* width, int* height );
void write_ppm( FILE* f, int width, int height, unsigned char* data );

main( int argc, char **argv )
{
	unsigned char* image;
	unsigned char* colimage;
	int width, height;
	int i;
	int max;
	unsigned char map[256][3];


	if ( argc != 2 )
	{
		fprintf( stderr, "usage: %s inputfile\n", argv[0] );
		exit( 1 );
	}

	image = read_pgm( argv[1], &width, &height );
	colimage = (unsigned char*)malloc( width * height * 3 );

    max = 0;
    for ( i = 0; i < width*height; ++i )
		if ( image[i] > max )
			max = image[i];

    for ( i = 1; i <= max; ++i )
		hsv_to_rgb( (i-1) * M_PI * 2 / max, 1.0, 1.0, map[i]+0, map[i]+1, map[i]+2 );

    for ( i = 0; i < width*height; ++i )
    {
		colimage[i*3+0] = map[image[i]][0];
		colimage[i*3+1] = map[image[i]][1];
		colimage[i*3+2] = map[image[i]][2];
	}

	write_ppm( stdout, width, height, colimage );

}

void hsv_to_rgb( double h, double s, double v,
		 unsigned char* r, unsigned char* g, unsigned char* b )
{
    int i;
    double f;
    unsigned char p, q, t, z;
     
    if ( s == 0 )
    {
		*r = *g = *b = v*255;
		return;
	}

    h /= (M_PI/3);

    i = h;
    f = h - i;

    p = 255 * v * (1-s);
    q = 255 * v * (1-s*f);
    t = 255 * v * (1-(s*(1-f)));
    z = 255 * v;

    *r = (i==0||i==5) ? z : ( (i==2||i==3) ? p : ( i==1 ? q : t ) );
    *g = (i==1||i==2) ? z : ( (i==4||i==5) ? p : ( i==3 ? q : t ) );
    *b = (i==3||i==4) ? z : ( (i==0||i==1) ? p : ( i==5 ? q : t ) );
}

unsigned char* read_pgm( char* filename, int* width, int* height )
{
    char buffer[80];
    int phase = 0;
    int type, maxval;
    int j;
    unsigned char* data;
    FILE* f;

    if ( strcmp( filename, "-" ) == 0 )
    {
		f = stdin;
	}
    else
    {
		f = fopen( filename, "rb" );
		if ( f == NULL )
			return NULL;
	}
     
    while ( phase < 4 )
    {
		fgets( buffer, 80, f );
		if ( buffer[0] == '#' ) continue;
		switch( phase )
		{
			case 0: j = sscanf( buffer, "P%d %d %d %d\n", &type, width, height, &maxval ); break;
			case 1: j = sscanf( buffer, "%d %d %d\n", width, height, &maxval ); break;
			case 2: j = sscanf( buffer, "%d %d\n", height, &maxval ); break;
			case 3: j = sscanf( buffer, "%d\n", &maxval ); break;
			case 4: j = 0; break;
		}
	phase += j;
    }

    if ( type != 5 )
    {
		fprintf( stderr, "bad input image format.\n" );
		return NULL;
    }

    data = (unsigned char*)malloc ( *width * *height );
    fread( data, *width * *height, 1, f );

    fclose( f );
     
    return data;
}

void write_ppm( FILE* f, int width, int height, unsigned char* data )
{
    fprintf( f, "P6\n%d %d\n%d\n", width, height, 255 );
    fwrite( data, width*height*3, 1, f );
    fclose( f );
}