potracelib_demo.c

Go to the documentation of this file.

/* Copyright (C) 2001-2007 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. */

/* A simple and self-contained demo of the potracelib API */

#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <stdlib.h>

#include "potracelib.h"

#define WIDTH 250
#define HEIGHT 250

/* ---------------------------------------------------------------------- */
/* auxiliary bitmap functions */

/* macros for writing individual bitmap pixels */
#define BM_WORDSIZE ((int)sizeof(potrace_word))
#define BM_WORDBITS (8*BM_WORDSIZE)
#define BM_HIBIT (((potrace_word)1)<<(BM_WORDBITS-1))
#define bm_scanline(bm, y) ((bm)->map + (y)*(bm)->dy)
#define bm_index(bm, x, y) (&bm_scanline(bm, y)[(x)/BM_WORDBITS])
#define bm_mask(x) (BM_HIBIT >> ((x) & (BM_WORDBITS-1)))
#define bm_range(x, a) ((int)(x) >= 0 && (int)(x) < (a))
#define bm_safe(bm, x, y) (bm_range(x, (bm)->w) && bm_range(y, (bm)->h))
#define BM_USET(bm, x, y) (*bm_index(bm, x, y) |= bm_mask(x))
#define BM_UCLR(bm, x, y) (*bm_index(bm, x, y) &= ~bm_mask(x))
#define BM_UPUT(bm, x, y, b) ((b) ? BM_USET(bm, x, y) : BM_UCLR(bm, x, y))
#define BM_PUT(bm, x, y, b) (bm_safe(bm, x, y) ? BM_UPUT(bm, x, y, b) : 0)

/* return new un-initialized bitmap. NULL with errno on error */
static potrace_bitmap_t *bm_new(int w, int h) {
  potrace_bitmap_t *bm;
  int dy = (w + BM_WORDBITS - 1) / BM_WORDBITS;

  bm = (potrace_bitmap_t *) malloc(sizeof(potrace_bitmap_t));
  if (!bm) {
    return NULL;
  }
  bm->w = w;
  bm->h = h;
  bm->dy = dy;
  bm->map = (potrace_word *) malloc(dy * h * BM_WORDSIZE);
  if (!bm->map) {
    free(bm);
    return NULL;
  }
  return bm;
}

/* free a bitmap */
static void bm_free(potrace_bitmap_t *bm) {
  if (bm != NULL) {
    free(bm->map);
  }
  free(bm);
}

/* ---------------------------------------------------------------------- */
/* demo */

int main() {
  int x, y, i;
  potrace_bitmap_t *bm;
  potrace_param_t *param;
  potrace_path_t *p;
  potrace_state_t *st;
  int n, *tag;
  potrace_dpoint_t (*c)[3];

  /* create a bitmap */
  bm = bm_new(WIDTH, HEIGHT);
  if (!bm) {
    fprintf(stderr, "Error allocating bitmap: %s\n", strerror(errno)); 
    return 1;
  }

  /* fill the bitmap with some pattern */
  for (y=0; y<HEIGHT; y++) {
    for (x=0; x<WIDTH; x++) {
      BM_PUT(bm, x, y, ((x*x + y*y*y) % 10000 < 5000) ? 1 : 0);
    }
  }

  /* set tracing parameters, starting from defaults */
  param = potrace_param_default();
  if (!param) {
    fprintf(stderr, "Error allocating parameters: %s\n", strerror(errno)); 
    return 1;
  }
  param->turdsize = 0;

  /* trace the bitmap */
  st = potrace_trace(param, bm);
  if (!st || st->status != POTRACE_STATUS_OK) {
    fprintf(stderr, "Error tracing bitmap: %s\n", strerror(errno));
    return 1;
  }
  bm_free(bm);
  
  /* output vector data, e.g. as a rudimentary EPS file */
  printf("%%!PS-Adobe-3.0 EPSF-3.0\n");
  printf("%%%%BoundingBox: 0 0 %d %d\n", WIDTH, HEIGHT);
  printf("gsave\n");

  /* draw each curve */
  p = st->plist;
  while (p != NULL) {
    n = p->curve.n;
    tag = p->curve.tag;
    c = p->curve.c;
    printf("%f %f moveto\n", c[n-1][2].x, c[n-1][2].y);
    for (i=0; i<n; i++) {
      switch (tag[i]) {
      case POTRACE_CORNER:
        printf("%f %f lineto\n", c[i][1].x, c[i][1].y);
        printf("%f %f lineto\n", c[i][2].x, c[i][2].y);
        break;
      case POTRACE_CURVETO:
        printf("%f %f %f %f %f %f curveto\n", 
               c[i][0].x, c[i][0].y,
               c[i][1].x, c[i][1].y,
               c[i][2].x, c[i][2].y);
        break;
      }
    }
    /* at the end of a group of a positive path and its negative
       children, fill. */
    if (p->next == NULL || p->next->sign == '+') {
      printf("0 setgray fill\n");
    }
    p = p->next;
  }
  printf("grestore\n");
  printf("%%EOF\n");
  
  potrace_state_free(st);
  potrace_param_free(param);

  return 0;
}