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/*********************************************************************/
/* ppmshift - shift lines of a picture left or right by x pixels */
/* Frank Neumann, October 1993 */
/* V1.1 16.11.1993 */
/* */
/* version history: */
/* V1.0 11.10.1993 first version */
/* V1.1 16.11.1993 Rewritten to be NetPBM.programming conforming */
/*********************************************************************/
#include "ppm.h"
/* global variables */
#ifdef AMIGA
static char *version = "$VER: ppmshift 1.1 (16.11.93)"; /* Amiga version identification */
#endif
/**************************/
/* start of main function */
/**************************/
int main(argc, argv)
int argc;
char *argv[];
{
FILE* ifp;
time_t timenow;
int argn, rows, cols, format, i = 0, j = 0;
pixel *srcrow, *destrow;
pixel *pP = NULL, *pP2 = NULL;
pixval maxval;
int shift, nowshift;
char *usage = "shift [ppmfile]\n shift: maximum number of pixels to shift a line by\n";
/* parse in 'default' parameters */
ppm_init(&argc, argv);
argn = 1;
/* parse in shift number */
if (argn == argc)
pm_usage(usage);
if (sscanf(argv[argn], "%d", &shift) != 1)
pm_usage(usage);
if (shift < 0)
pm_error("shift factor must be 0 or more");
++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 first data from file */
ppm_readppminit(ifp, &cols, &rows, &maxval, &format);
if (shift > cols)
{
shift = cols;
pm_message("shift amount is larger than picture width - reset to %d", shift);
}
/* no error checking required here, ppmlib does it all for us */
srcrow = ppm_allocrow(cols);
/* allocate a row of pixel data for the new pixels */
destrow = ppm_allocrow(cols);
ppm_writeppminit(stdout, cols, rows, maxval, 0);
/* get time of day to feed the random number generator */
timenow = time(NULL);
srandom(timenow);
/** now do the shifting **/
/* the range by which a line is shifted lays in the range from */
/* -shift/2 .. +shift/2 pixels; however, within this range it is */
/* randomly chosen */
for (i = 0; i < rows; i++)
{
if (shift != 0)
nowshift = (random() % (shift+1)) - ((shift+1) / 2);
else
nowshift = 0;
ppm_readppmrow(ifp, srcrow, cols, maxval, format);
pP = srcrow;
pP2 = destrow;
/* if the shift value is less than zero, we take the original pixel line and */
/* copy it into the destination line translated to the left by x pixels. The */
/* empty pixels on the right end of the destination line are filled up with */
/* the pixel that is the right-most in the original pixel line. */
if (nowshift < 0)
{
pP+= abs(nowshift);
for (j = 0; j < cols; j++)
{
PPM_ASSIGN(*pP2, PPM_GETR(*pP), PPM_GETG(*pP), PPM_GETB(*pP));
pP2++;
if (j < (cols+nowshift)-1)
pP++;
}
}
/* if the shift value is 0 or positive, the first <nowshift> pixels of the */
/* destination line are filled with the first pixel from the source line, */
/* and the rest of the source line is copied to the dest line */
else
{
for (j = 0; j < cols; j++)
{
PPM_ASSIGN(*pP2, PPM_GETR(*pP), PPM_GETG(*pP), PPM_GETB(*pP));
pP2++;
if (j >= nowshift)
pP++;
}
}
/* write out one line of graphic data */
ppm_writeppmrow(stdout, destrow, cols, maxval, 0);
}
pm_close(ifp);
ppm_freerow(srcrow);
ppm_freerow(destrow);
exit(0);
}
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