kicad/potrace/curve.h

/* Copyright (C) 2001-2015 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. */

#ifndef CURVE_H
#define CURVE_H

#include "auxiliary.h"

/* vertex is c[1] for tag=POTRACE_CORNER, and the intersection of
 *  .c[-1][2]..c[0] and c[1]..c[2] for tag=POTRACE_CURVETO. alpha is only
 *  defined for tag=POTRACE_CURVETO and is the alpha parameter of the curve:
 *  .c[-1][2]..c[0] = alpha*(.c[-1][2]..vertex), and
 *  c[2]..c[1] = alpha*(c[2]..vertex).
 *  Beta is so that (.beta[i])[.vertex[i],.vertex[i+1]] = .c[i][2].
 */

struct privcurve_s
{
    int n;              /* number of segments */
    int* tag;           /* tag[n]: POTRACE_CORNER or POTRACE_CURVETO */
    dpoint_t( *c )[3];  /* c[n][i]: control points.
                         *  c[n][0] is unused for tag[n]=POTRACE_CORNER */
    /* the remainder of this structure is special to privcurve, and is
     *  used in EPS debug output and special EPS "short coding". These
     *  fields are valid only if "alphacurve" is set. */
    int alphacurve;     /* have the following fields been initialized? */
    dpoint_t*   vertex; /* for POTRACE_CORNER, this equals c[1] */
    double*     alpha;  /* only for POTRACE_CURVETO */
    double*     alpha0; /* "uncropped" alpha parameter - for debug output only */
    double*     beta;
};
typedef struct privcurve_s privcurve_t;

struct sums_s
{
    double  x;
    double  y;
    double  x2;
    double  xy;
    double  y2;
};
typedef struct sums_s sums_t;

/* the path structure is filled in with information about a given path
 *  as it is accumulated and passed through the different stages of the
 *  Potrace algorithm. Backends only need to read the fcurve and fm
 *  fields of this data structure, but debugging backends may read
 *  other fields. */
struct potrace_privpath_s
{
    int len;
    point_t* pt;            /* pt[len]: path as extracted from bitmap */
    int* lon;               /* lon[len]: (i,lon[i]) = longest straight line from i */

    int x0, y0;             /* origin for sums */
    sums_t* sums;           /* sums[len+1]: cache for fast summing */

    int m;                  /* length of optimal polygon */
    int* po;                /* po[m]: optimal polygon */

    privcurve_t curve;      /* curve[m]: array of curve elements */
    privcurve_t ocurve;     /* ocurve[om]: array of curve elements */
    privcurve_t* fcurve;    /* final curve: this points to either curve or
                             *  ocurve. Do not free this separately. */
};
typedef struct potrace_privpath_s potrace_privpath_t;

/* shorter names */
typedef potrace_privpath_t  privpath_t;
typedef potrace_path_t      path_t;

path_t* path_new( void );
void    path_free( path_t* p );
void    pathlist_free( path_t* plist );
int     privcurve_init( privcurve_t* curve, int n );
void    privcurve_to_curve( privcurve_t* pc, potrace_curve_t* c );

#endif /* CURVE_H */