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/* pnmedge.c - edge-detection
**
** Copyright (C) 1989 by Jef Poskanzer.
** modified for pnm by Peter Kirchgessner, 1995.
**
** Permission to use, copy, modify, and distribute this software and its
** documentation for any purpose and without fee is hereby granted, provided
** that the above copyright notice appear in all copies and that both that
** copyright notice and this permission notice appear in supporting
** documentation. This software is provided "as is" without express or
** implied warranty.
*/
#include <math.h>
#include "pm_c_util.h"
#include "pam.h"
static void
writeBlackRow(struct pam * const pamP) {
tuple * const tuplerow = pnm_allocpamrow(pamP);
unsigned int col;
for (col = 0; col < pamP->width; ++col) {
unsigned int plane;
for (plane = 0; plane < pamP->depth; ++plane)
tuplerow[col][plane] = 0;
}
pnm_writepamrow(pamP, tuplerow);
}
static void
rotateRows(tuple ** const row0P,
tuple ** const row1P,
tuple ** const row2P) {
/* Rotate rows. */
tuple * const formerRow0 = *row0P;
*row0P = *row1P;
*row1P = *row2P;
*row2P = formerRow0;
}
static long
horizGradient(tuple * const tuplerow,
unsigned int const col,
unsigned int const plane) {
return (long)tuplerow[col+1][plane] - (long)tuplerow[col-1][plane];
}
static long
horizAvg(tuple * const tuplerow,
unsigned int const col,
unsigned int const plane) {
return
1 * (long)tuplerow[col-1][plane] +
2 * (long)tuplerow[col ][plane] +
1 * (long)tuplerow[col+1][plane];
}
static void
computeOneRow(struct pam * const inpamP,
struct pam * const outpamP,
tuple * const row0,
tuple * const row1,
tuple * const row2,
tuple * const orow) {
/*----------------------------------------------------------------------------
Compute an output row from 3 input rows.
The input rows must have the same maxval as the output row.
-----------------------------------------------------------------------------*/
unsigned int plane;
for (plane = 0; plane < inpamP->depth; ++plane) {
unsigned int col;
/* Left column is black */
orow[0][plane] = 0;
for (col = 1; col < inpamP->width - 1; ++col) {
double const grad1 =
1 * horizGradient(row0, col, plane) +
2 * horizGradient(row1, col, plane) +
1 * horizGradient(row2, col, plane);
double const grad2 =
horizAvg(row2, col, plane) - horizAvg(row0, col, plane);
double const gradient = sqrt(SQR(grad1) + SQR(grad2));
/* apply arbitrary scaling factor and maxval clipping */
orow[col][plane] = MIN(outpamP->maxval, (long)(gradient / 1.8));
/* Right column is black */
orow[inpamP->width - 1][plane] = 0;
}
}
}
static void
writeMiddleRows(struct pam * const inpamP,
struct pam * const outpamP) {
tuple *row0, *row1, *row2;
tuple *orow, *irow;
unsigned int row;
irow = pnm_allocpamrow(inpamP);
orow = pnm_allocpamrow(outpamP);
row0 = pnm_allocpamrow(outpamP);
row1 = pnm_allocpamrow(outpamP);
row2 = pnm_allocpamrow(outpamP);
/* Read in the first two rows. */
pnm_readpamrow(inpamP, irow);
pnm_scaletuplerow(inpamP, row0, irow, outpamP->maxval);
pnm_readpamrow(inpamP, irow);
pnm_scaletuplerow(inpamP, row1, irow, outpamP->maxval);
pm_message("row1[0][0]=%lu", row1[0][0]);
for (row = 1; row < inpamP->height - 1; ++row) {
/* Read in the next row and write out the current row. */
pnm_readpamrow(inpamP, irow);
pnm_scaletuplerow(inpamP, row2, irow, outpamP->maxval);
computeOneRow(inpamP, outpamP, row0, row1, row2, orow);
pnm_writepamrow(outpamP, orow);
rotateRows(&row0, &row1, &row2);
}
pnm_freepamrow(orow);
pnm_freepamrow(row2);
pnm_freepamrow(row1);
pnm_freepamrow(row0);
}
int
main(int argc, char *argv[]) {
FILE *ifP;
struct pam inpam, outpam;
pnm_init( &argc, argv );
if (argc-1 == 1)
ifP = pm_openr(argv[1]);
else if (argc-1 == 0)
ifP = stdin;
else
pm_error("Too many arguments. Program takes at most 1 argument: "
"input file name");
pnm_readpaminit(ifP, &inpam, PAM_STRUCT_SIZE(tuple_type));
if (inpam.width < 3)
pm_error("Image is %u columns wide. It must be at least 3.",
inpam.width);
if (inpam.height < 3)
pm_error("Image is %u rows high. It must be at least 3.",
inpam.height);
outpam = inpam;
outpam.file = stdout;
if (PAM_FORMAT_TYPE(inpam.format) == PBM_TYPE) {
outpam.format = PGM_FORMAT;
outpam.maxval = 255;
}
pnm_writepaminit(&outpam);
/* First row is black: */
writeBlackRow(&outpam );
writeMiddleRows(&inpam, &outpam);
pm_close(ifP);
/* Last row is black: */
writeBlackRow(&outpam);
pm_close(stdout);
return 0;
}
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