/* imghisteq.c
 *
 * Program to read a masked or unmasked v7.2 img file and dump cumulative
 * histogram in 5 mGal steps between -100 and +100 mGal.
 *
 * MODIFIED 9 July 1996 to comment out the track encoding.  Also added
 * test for itest < 0, and shifted cumulative backward by 0.5
 *
 * W. H. F. Smith, 30 January 1996
 *
 */

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

#define NXIN 10800	/* Number of pixels in a v7.2 row (360x30)  */
#define NY72 6336	/* Number of rows in a v7.2 file  */
#define NHIST 41	/* Number of cells for histogram of 5 mGal steps  */

short buffline[NXIN];

int hist[NHIST];

main(argc, argv)
int	argc;
char	**argv;
{
	FILE	*fp;
	int	i, j, k, itest, ntot;

	if (argc != 2 || (fp = fopen(argv[1], "r")) == NULL) {
		fprintf(stderr,"usage:  imghisteq <img 7.2 filename>.\n");
		exit(-1);
	}

	for (i = 0; i < NHIST; i++) hist[i] = 0;

	ntot = 0;

	for (j = 0; j < NY72; j++) {
		if ( (fread(buffline, 2, NXIN, fp)) != NXIN) {
			fprintf(stderr,"imghisteq:  READ ERROR.  j = %d\n", j);
			exit(-1);
		}
		for (i = 0; i < NXIN; i++) {
			if (buffline[i] == 32767) continue;
			ntot++;
/*			if (buffline[i]%2) buffline[i] --;	*/
			itest = ceil((double)(buffline[i] + 1000)/(double)50);
			if (itest < 0) itest = 0;
			for (k = itest; k < NHIST; k++) hist[k]++;
		}
	}
	fclose(fp);

	for (k = 0; k < NHIST; k++) {
		printf("%d\t%.8lg\n", 5*k - 100, ((double)hist[k]-0.5)/(double)ntot);
	}


	exit(0);
}