/*
 *  A sample code drawing an image with gnuplot
 *  A.Date 
 *  3 May 2009
 *
 */

#include <stdlib.h>  /*  drand48() */
#include <stdio.h>

#define N_XPIXELS 20
#define N_YPIXELS 20
#define RAND_SEED 20090503
#define SLEEP 100000000

void write_2d_data(unsigned char *img);
unsigned char *alloc_1d_uchar(int n);

FILE *gp;

int main (int argc, char *argv[] )
{ 
	int i, n;
	int nx, ny;
	unsigned char *img;
	long seed = RAND_SEED; 
	
	srand48(seed);

	nx = N_XPIXELS;
	ny = N_YPIXELS;
	n = nx*ny;
	img = alloc_1d_uchar(n); 

	for (i=0; i < n; i++){
		img[i] = (unsigned char)(255.0*drand48());
	}

	gp = popen("gnuplot -geometry 480x480","w");

//	gp = popen("gnuplot","w");
//	fprintf(gp, "set terminal postscript eps color \"Times\" 20\n");
//	fprintf(gp, "set terminal tgif\n");
//      fprintf(gp, "set term x11\n");

	fprintf(gp, "set yrange [] reverse\n");
	fprintf(gp, "unset key\n");

//  fprintf(gp, "set out 'image000.eps'\n");
//  fprintf(gp, "set out 'image000.obj'\n");

	fprintf(gp, "plot '-' matrix with image\n");

	write_2d_data(img); 
	fprintf(gp,"e\n");
	fprintf(gp,"e\n");
	fflush(gp); 

	usleep(SLEEP); /* comment out when generate a file */

	fclose(gp);
	free(img);

}

/* write data for gnuplot */
void write_2d_data(unsigned char *img){

        int n_pixels = N_XPIXELS*N_YPIXELS;
        int i;

        for (i=0; i<n_pixels; i++){
                fprintf(gp, "%d ", img[i]);
                if (  (i+1)%N_XPIXELS  ==  0 ){
                        fprintf(gp, "\n");
                }
        }
}


/*** Allocate 1d array of uchars ***/
unsigned char *alloc_1d_uchar(int n){

	unsigned char *new;
	new = (unsigned char *) malloc ((unsigned) (n * sizeof (char)));
	if (new == NULL) {
		printf("ALLOC_1D_CHAR: Couldn't allocate array of uchars\n");
		return (NULL);
	}
	return (new);

}