libart-lgpl/art_vpath.c

/* Libart_LGPL - library of basic graphic primitives
 * Copyright (C) 1998-2000 Raph Levien
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

/* Basic constructors and operations for vector paths */

#include "config.h"
#include "art_vpath.h"

#include <math.h>
#include <stdlib.h>

#include "art_misc.h"

#include "art_rect.h"

/**
 * art_vpath_add_point: Add point to vpath.
 * @p_vpath: Where the pointer to the #ArtVpath structure is stored.
 * @pn_points: Pointer to the number of points in *@p_vpath.
 * @pn_points_max: Pointer to the number of points allocated.
 * @code: The pathcode for the new point.
 * @x: The X coordinate of the new point.
 * @y: The Y coordinate of the new point.
 *
 * Adds a new point to *@p_vpath, reallocating and updating *@p_vpath
 * and *@pn_points_max as necessary. *@pn_points is incremented.
 *
 * This routine always adds the point after all points already in the
 * vpath. Thus, it should be called in the order the points are
 * desired.
 **/
void
art_vpath_add_point (ArtVpath **p_vpath, int *pn_points, int *pn_points_max,
		     ArtPathcode code, double x, double y)
{
  int i;

  i = (*pn_points)++;
  if (i == *pn_points_max)
    art_expand (*p_vpath, ArtVpath, *pn_points_max);
  (*p_vpath)[i].code = code;
  (*p_vpath)[i].x = x;
  (*p_vpath)[i].y = y;
}

/* number of steps should really depend on radius. */
#define CIRCLE_STEPS 128

/**
 * art_vpath_new_circle: Create a new circle.
 * @x: X coordinate of center.
 * @y: Y coordinate of center.
 * @r: radius.
 *
 * Creates a new polygon closely approximating a circle with center
 * (@x, @y) and radius @r. Currently, the number of points used in the
 * approximation is fixed, but that will probably change.
 *
 * Return value: The newly created #ArtVpath.
 **/
ArtVpath *
art_vpath_new_circle (double x, double y, double r)
{
  int i;
  ArtVpath *vec;
  double theta;

  vec = art_new (ArtVpath, CIRCLE_STEPS + 2);

  for (i = 0; i < CIRCLE_STEPS + 1; i++)
    {
      vec[i].code = i ? ART_LINETO : ART_MOVETO;
      theta = (i & (CIRCLE_STEPS - 1)) * (M_PI * 2.0 / CIRCLE_STEPS);
      vec[i].x = x + r * cos (theta);
      vec[i].y = y - r * sin (theta);
    }
  vec[i].code = ART_END;

  return vec;
}

/**
 * art_vpath_affine_transform: Affine transform a vpath.
 * @src: Source vpath to transform.
 * @matrix: Affine transform.
 *
 * Computes the affine transform of the vpath, using @matrix as the
 * transform. @matrix is stored in the same format as PostScript, ie.
 * x' = @matrix[0] * x + @matrix[2] * y + @matrix[4]
 * y' = @matrix[1] * x + @matrix[3] * y + @matrix[5]
 *
 * Return value: the newly allocated vpath resulting from the transform.
**/
ArtVpath *
art_vpath_affine_transform (const ArtVpath *src, const double matrix[6])
{
  int i;
  int size;
  ArtVpath *new;
  double x, y;

  for (i = 0; src[i].code != ART_END; i++);
  size = i;

  new = art_new (ArtVpath, size + 1);

  for (i = 0; i < size; i++)
    {
      new[i].code = src[i].code;
      x = src[i].x;
      y = src[i].y;
      new[i].x = matrix[0] * x + matrix[2] * y + matrix[4];
      new[i].y = matrix[1] * x + matrix[3] * y + matrix[5];
    }
  new[i].code = ART_END;

  return new;
}

/**
 * art_vpath_bbox_drect: Determine bounding box of vpath.
 * @vec: Source vpath.
 * @drect: Where to store bounding box.
 *
 * Determines bounding box of @vec, and stores it in @drect.
 **/
void
art_vpath_bbox_drect (const ArtVpath *vec, ArtDRect *drect)
{
  int i;
  double x0, y0, x1, y1;

  if (vec[0].code == ART_END)
    {
      x0 = y0 = x1 = y1 = 0;
    }
  else
    {
      x0 = x1 = vec[0].x;
      y0 = y1 = vec[0].y;
      for (i = 1; vec[i].code != ART_END; i++)
	{
	  if (vec[i].x < x0) x0 = vec[i].x;
	  if (vec[i].x > x1) x1 = vec[i].x;
	  if (vec[i].y < y0) y0 = vec[i].y;
	  if (vec[i].y > y1) y1 = vec[i].y;
	}
    }
  drect->x0 = x0;
  drect->y0 = y0;
  drect->x1 = x1;
  drect->y1 = y1;
}

/**
 * art_vpath_bbox_irect: Determine integer bounding box of vpath.
 * @vec: Source vpath.
 * idrect: Where to store bounding box.
 *
 * Determines integer bounding box of @vec, and stores it in @irect.
 **/
void
art_vpath_bbox_irect (const ArtVpath *vec, ArtIRect *irect)
{
  ArtDRect drect;

  art_vpath_bbox_drect (vec, &drect);
  art_drect_to_irect (irect, &drect);
}

#define PERTURBATION 2e-3

/**
 * art_vpath_perturb: Perturb each point in vpath by small random amount.
 * @src: Source vpath.
 *
 * Perturbs each of the points by a small random amount. This is
 * helpful for cheating in cases when algorithms haven't attained
 * numerical stability yet.
 *
 * Return value: Newly allocated vpath containing perturbed @src.
 **/ 
ArtVpath *
art_vpath_perturb (ArtVpath *src)
{
  int i;
  int size;
  ArtVpath *new;
  double x, y;
  double x_start, y_start;
  int open;

  for (i = 0; src[i].code != ART_END; i++);
  size = i;

  new = art_new (ArtVpath, size + 1);

  x_start = 0;
  y_start = 0;
  open = 0;
  for (i = 0; i < size; i++)
    {
      new[i].code = src[i].code;
      x = src[i].x + (PERTURBATION * rand ()) / RAND_MAX - PERTURBATION * 0.5;
      y = src[i].y + (PERTURBATION * rand ()) / RAND_MAX - PERTURBATION * 0.5;
      if (src[i].code == ART_MOVETO)
	{
	  x_start = x;
	  y_start = y;
	  open = 0;
	}
      else if (src[i].code == ART_MOVETO_OPEN)
	open = 1;
      if (!open && (i + 1 == size || src[i + 1].code != ART_LINETO))
	{
	  x = x_start;
	  y = y_start;
	}
      new[i].x = x;
      new[i].y = y;
    }
  new[i].code = ART_END;

  return new;
}