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/*********************************************************************/
/* ppmspread - randomly displace a PPM's pixels by a certain amount */
/* Frank Neumann, October 1993 */
/* V1.1 16.11.1993 */
/* */
/* version history: */
/* V1.0 12.10.1993 first version */
/* V1.1 16.11.1993 Rewritten to be NetPBM.programming conforming */
/*********************************************************************/
#include <string.h>
#include "ppm.h"
/* global variables */
#ifdef AMIGA
static char *version = "$VER: ppmspread 1.1 (16.11.93)"; /* Amiga version identification */
#endif
/**************************/
/* start of main function */
/**************************/
int main(argc, argv)
int argc;
char *argv[];
{
FILE* ifp;
int argn, rows, cols, i, j;
int xdis, ydis, xnew, ynew;
pixel **destarray, **srcarray;
pixel *pP, *pP2;
pixval maxval;
pixval r1, g1, b1;
int amount;
time_t timenow;
const char * const usage = "amount [ppmfile]\n amount: # of pixels to displace a pixel by at most\n";
/* parse in 'default' parameters */
ppm_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 = ppm_readppm(ifp, &cols, &rows, &maxval);
/* allocate an entire picture buffer for dest picture */
destarray = ppm_allocarray(cols, rows);
/* clear out the buffer */
for (i=0; i < rows; i++)
memset(destarray[i], 0, cols * sizeof(pixel));
/* set seed for random number generator */
/* get time of day to feed the random number generator */
timenow = time(NULL);
srand(timenow);
/* start displacing pixels */
for (i = 0; i < rows; i++)
{
pP = srcarray[i];
for (j = 0; j < cols; j++)
{
xdis = (rand() % (amount+1)) - ((amount+1) / 2);
ydis = (rand() % (amount+1)) - ((amount+1) / 2);
xnew = j + xdis;
ynew = i + ydis;
/* only set the displaced pixel if it's within the bounds of the image */
if (xnew >= 0 && xnew < cols && ynew >= 0 && ynew < rows)
{
/* displacing a pixel is accomplished by swapping it with another */
/* pixel in its vicinity - so, first store other pixel's RGB */
pP2 = srcarray[ynew] + xnew;
r1 = PPM_GETR(*pP2);
g1 = PPM_GETG(*pP2);
b1 = PPM_GETB(*pP2);
/* set second pixel to new value */
pP2 = destarray[ynew] + xnew;
PPM_ASSIGN(*pP2, PPM_GETR(*pP), PPM_GETG(*pP), PPM_GETB(*pP));
/* now, set first pixel to (old) value of second */
pP2 = destarray[i] + j;
PPM_ASSIGN(*pP2, r1, g1, b1);
}
else
{
/* displaced pixel is out of bounds; leave the old pixel there */
pP2 = destarray[i] + j;
PPM_ASSIGN(*pP2, PPM_GETR(*pP), PPM_GETG(*pP), PPM_GETB(*pP));
}
pP++;
}
}
/* write out entire dest picture in one go */
ppm_writeppm(stdout, destarray, cols, rows, maxval, 0);
pm_close(ifp);
ppm_freearray(srcarray, rows);
ppm_freearray(destarray, rows);
exit(0);
}
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