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/* Copyright (C) 2001-2019 Peter Selinger.
This file is part of Potrace. It is free software and it is covered
by the GNU General Public License. See the file COPYING for details. */
/* The GeoJSON backend of Potrace. */
/* Written 2012 by Christoph Hormann <chris_hormann@gmx.de> */
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <stdio.h>
#include <stdarg.h>
#include <string.h>
#include <math.h>
#include "potracelib.h"
#include "curve.h"
#include "main.h"
#include "backend_geojson.h"
#include "lists.h"
#include "auxiliary.h"
/* ---------------------------------------------------------------------- */
/* auxiliary */
/* return a point on a 1-dimensional Bezier segment */
static inline double bezier(double t, double x0, double x1, double x2, double x3) {
double s = 1-t;
return s*s*s*x0 + 3*(s*s*t)*x1 + 3*(t*t*s)*x2 + t*t*t*x3;
}
static const char *format = "%f";
/* Convert a floating-point number to a string, using a pre-determined
format. The format must be previously set with set_format().
Returns one of a small number of statically allocated strings. */
static char *round_to_unit(double x) {
static int n = 0;
static char buf[4][100];
n++;
if (n >= 4) {
n = 0;
}
sprintf(buf[n], format, x);
return buf[n];
}
/* Select a print format for floating point numbers, appropriate for
the given scaling and info.unit. Note: the format must be so that
the resulting number fits into a buffer of size 100. */
static void set_format(trans_t tr) {
double s;
int d;
static char buf[10];
s = min(fabs(tr.scalex), fabs(tr.scaley));
if (info.unit != 0.0 && s != 0.0) {
d = (int)ceil(log(info.unit/s) / log(10));
} else {
d = 0;
}
if (d <= 0) {
format = "%.0f";
} else if (d <= 20) {
sprintf(buf, "%%.%df", d);
format = buf;
} else {
format = "%e";
}
}
/* ---------------------------------------------------------------------- */
/* path-drawing auxiliary functions */
static dpoint_t cur;
static void geojson_moveto(FILE *fout, dpoint_t p, trans_t tr) {
dpoint_t q;
q = trans(p, tr);
fprintf(fout, "[%s, %s]", round_to_unit(q.x), round_to_unit(q.y));
cur = q;
}
static void geojson_lineto(FILE *fout, dpoint_t p, trans_t tr) {
dpoint_t q;
q = trans(p, tr);
fprintf(fout, ", [%s, %s]", round_to_unit(q.x), round_to_unit(q.y));
cur = q;
}
static void geojson_curveto(FILE *fout, dpoint_t p1, dpoint_t p2, dpoint_t p3, trans_t tr) {
dpoint_t q1;
dpoint_t q2;
dpoint_t q3;
double step, t;
int i;
double x, y;
q1 = trans(p1, tr);
q2 = trans(p2, tr);
q3 = trans(p3, tr);
step = 1.0 / 8.0;
for (i=0, t=step; i<8; i++, t+=step) {
x = bezier(t, cur.x, q1.x, q2.x, q3.x);
y = bezier(t, cur.y, q1.y, q2.y, q3.y);
fprintf(fout, ", [%s, %s]", round_to_unit(x), round_to_unit(y));
}
cur = q3;
}
/* ---------------------------------------------------------------------- */
/* functions for converting a path to an SVG path element */
static int geojson_path(FILE *fout, potrace_curve_t *curve, trans_t tr) {
int i;
dpoint_t *c;
int m = curve->n;
fprintf(fout, " [");
c = curve->c[m-1];
geojson_moveto(fout, c[2], tr);
for (i=0; i<m; i++) {
c = curve->c[i];
switch (curve->tag[i]) {
case POTRACE_CORNER:
geojson_lineto(fout, c[1], tr);
geojson_lineto(fout, c[2], tr);
break;
case POTRACE_CURVETO:
geojson_curveto(fout, c[0], c[1], c[2], tr);
break;
}
}
fprintf(fout, " ]");
return 0;
}
static void write_polygons(FILE *fout, potrace_path_t *tree, trans_t tr, int first) {
potrace_path_t *p, *q;
for (p=tree; p; p=p->sibling) {
if (!first) fprintf(fout, ",\n");
fprintf(fout, "{ \"type\": \"Feature\",\n");
fprintf(fout, " \"properties\": { },\n");
fprintf(fout, " \"geometry\": {\n");
fprintf(fout, " \"type\": \"Polygon\",\n");
fprintf(fout, " \"coordinates\": [\n");
geojson_path(fout, &p->curve, tr);
for (q=p->childlist; q; q=q->sibling) {
fprintf(fout, ",\n");
geojson_path(fout, &q->curve, tr);
}
fprintf(fout, " ]\n");
fprintf(fout, " }\n");
fprintf(fout, "}");
for (q=p->childlist; q; q=q->sibling) {
write_polygons(fout, q->childlist, tr, 0);
}
first = 0;
}
}
/* ---------------------------------------------------------------------- */
/* Backend. */
/* public interface for GeoJSON */
int page_geojson(FILE *fout, potrace_path_t *plist, imginfo_t *imginfo) {
trans_t tr;
/* set up the coordinate transform (rotation) */
tr.bb[0] = imginfo->trans.bb[0]+imginfo->lmar+imginfo->rmar;
tr.bb[1] = imginfo->trans.bb[1]+imginfo->tmar+imginfo->bmar;
tr.orig[0] = imginfo->trans.orig[0]+imginfo->lmar;
tr.orig[1] = imginfo->trans.orig[1]+imginfo->bmar;
tr.x[0] = imginfo->trans.x[0];
tr.x[1] = imginfo->trans.x[1];
tr.y[0] = imginfo->trans.y[0];
tr.y[1] = imginfo->trans.y[1];
/* set the print format for floating point numbers */
set_format(imginfo->trans);
/* header */
fprintf(fout, "{\n");
fprintf(fout, "\"type\": \"FeatureCollection\",\n");
fprintf(fout, "\"features\": [\n");
write_polygons(fout, plist, tr, 1);
/* write footer */
fprintf(fout, "\n]\n");
fprintf(fout, "}\n");
fflush(fout);
return 0;
}
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