/*********************************************************************/
/* pnmspread -  randomly displace a PPM's xels by a certain amount */
/* Frank Neumann, October 1993                                       */
/* V1.2 27.11.1999                                                   */
/*                                                                   */
/* version history:                                                  */
/* V1.0 12.10.1993    first version                                  */
/* V1.1 16.11.1993    Rewritten to be NetPBM.programming conforming  */
/* V1.2 27.11.1999    Promoted from ppmspread to pnmspread.          */
/*********************************************************************/

#include <time.h>
#include "pnm.h"

/* global variables */
#ifdef AMIGA
static char *version = "$VER: pnmspread 1.2 (27.11.99)"; /* Amiga version identification */
#endif

/**************************/
/* start of main function */
/**************************/
int
main( int argc, char* argv[] )
{
	FILE* ifp;
	int argn, rows, cols, format, i, j;
	int xdis, ydis, xnew, ynew;
	xel **destarray, **srcarray;
	xel *xP, *xP2;
	xelval maxval;
	xel x;
	int amount;
	char *usage = "amount [pnmfile]\n        amount: # of xels to displace a xel by at most\n";

	/* parse in 'default' parameters */
	pnm_init(&argc, argv);

	argn = 1;

	/* parse in amount & seed */
	if (argn == argc)
		pm_usage(usage);
	if (sscanf(argv[argn], "%d", &amount) != 1)
		pm_usage(usage);
	if (amount < 0)
		pm_error("amount should be a positive number");
	++argn;

	/* parse in filename (if present, stdin otherwise) */
	if (argn != argc)
	{
		ifp = pm_openr(argv[argn]);
		++argn;
	}
	else
		ifp = stdin;

	if (argn != argc)
		pm_usage(usage);

	/* read entire picture into buffer */
	srcarray = pnm_readpnm(ifp, &cols, &rows, &maxval, &format);

	/* allocate an entire picture buffer for dest picture */
	destarray = pnm_allocarray(cols, rows);

	/* clear out the buffer */
	for (i=0; i < rows; i++)
		bzero(destarray[i], cols * sizeof(xel));

	/* set seed for random number generator */
	/* get time of day to feed the random number generator */
	srandom( time( (time_t*) 0 ) );

	/* start displacing xels */
	for (i = 0; i < rows; i++)
	{
		xP = srcarray[i];

		for (j = 0; j < cols; j++)
		{
			xdis = (random() % (amount+1)) - ((amount+1) / 2);
			ydis = (random() % (amount+1)) - ((amount+1) / 2);

			xnew = j + xdis;
			ynew = i + ydis;

			/* only set the displaced xel if it's within the bounds of the image */
			if (xnew >= 0 && xnew < cols && ynew >= 0 && ynew < rows)
			{
				/* displacing a xel is accomplished by swapping it with another */
				/* xel in its vicinity - so, first store other xel's RGB      */
				xP2 = srcarray[ynew] + xnew;
				x = *xP2;
				/* set second xel to new value */
				xP2 = destarray[ynew] + xnew;
				*xP2 = *xP;
				/* now, set first xel to (old) value of second*/
				xP2 = destarray[i] + j;
				*xP2 = x;
			}
			else
			{
                /* displaced xel is out of bounds; leave the old xel there */
                xP2 = destarray[i] + j;
				*xP2 = *xP;
			}
			xP++;
		}
	}

	/* write out entire dest picture in one go */
	pnm_writepnm(stdout, destarray, cols, rows, maxval, format, 0);

	pm_closer(ifp);
	pm_closew(stdout);
	pnm_freearray(srcarray, rows);
	pnm_freearray(destarray, rows);

	exit(0);
}