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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"
/**************************/
/* start of main function */
/**************************/
int
main(int argc,
char * argv[]) {
FILE * ifP;
unsigned int row;
int argn, rows, cols, format;
pixel * srcrow;
pixel * destrow;
pixval maxval;
int shift, nowshift;
int shiftArg;
const char * const 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", &shiftArg) != 1)
pm_usage(usage);
if (shiftArg < 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 (shiftArg > cols) {
shift = cols;
pm_message("shift amount is larger than picture width - reset to %d",
shift);
} else
shift = shiftArg;
srcrow = ppm_allocrow(cols);
destrow = ppm_allocrow(cols);
ppm_writeppminit(stdout, cols, rows, maxval, 0);
srand(pm_randseed());
/** 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 (row = 0; row < rows; ++row) {
pixel * pP;
pixel * pP2;
if (shift != 0)
nowshift = (rand() % (shift+1)) - ((shift+1) / 2);
else
nowshift = 0;
ppm_readppmrow(ifP, srcrow, cols, maxval, format);
pP = &srcrow[0];
pP2 = &destrow[0];
/* 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) {
unsigned int col;
pP += abs(nowshift);
for (col = 0; col < cols; ++col) {
PPM_ASSIGN(*pP2, PPM_GETR(*pP), PPM_GETG(*pP), PPM_GETB(*pP));
++pP2;
if (col < (cols + nowshift) - 1)
++pP;
}
} else {
unsigned int col;
/* The shift value is 0 or positive, so fill the first
<nowshift> pixels of the destination line with the
first pixel from the source line, and copy the rest of
the source line to the dest line
*/
for (col = 0; col < cols; ++col) {
PPM_ASSIGN(*pP2, PPM_GETR(*pP), PPM_GETG(*pP), PPM_GETB(*pP));
++pP2;
if (col >= nowshift)
++pP;
}
}
ppm_writeppmrow(stdout, destrow, cols, maxval, 0);
}
pm_close(ifP);
ppm_freerow(srcrow);
ppm_freerow(destrow);
return 0;
}
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