234 lines
6.0 KiB
C
234 lines
6.0 KiB
C
/* spline.c: spline and spline list (represented as arrays) manipulation.
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*
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* Copyright (C) 1992 Free Software Foundation, Inc.
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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#include "config.h"
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#include <assert.h>
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#include <glib.h>
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#include "global.h"
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#include "bounding-box.h"
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#include "spline.h"
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#include "vector.h"
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/* Return a new spline structure, initialized with (recognizable)
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garbage. */
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spline_type
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new_spline (void)
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{
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real_coordinate_type coord = { -100.0, -100.0 };
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spline_type spline;
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START_POINT (spline)
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= CONTROL1 (spline)
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= CONTROL2 (spline)
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= END_POINT (spline)
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= coord;
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SPLINE_DEGREE (spline) = -1;
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SPLINE_LINEARITY (spline) = 0;
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return spline;
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}
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/* Print a spline in human-readable form. */
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void
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print_spline (FILE *f, spline_type s)
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{
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if (SPLINE_DEGREE (s) == LINEAR)
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fprintf (f, "(%.3f,%.3f)--(%.3f,%.3f).\n",
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START_POINT (s).x, START_POINT (s).y,
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END_POINT (s).x, END_POINT (s).y);
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else if (SPLINE_DEGREE (s) == CUBIC)
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fprintf (f, "(%.3f,%.3f)..ctrls(%.3f,%.3f)&(%.3f,%.3f)..(%.3f,%.3f).\n",
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START_POINT (s).x, START_POINT (s).y,
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CONTROL1 (s).x, CONTROL1 (s).y,
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CONTROL2 (s).x, CONTROL2 (s).y,
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END_POINT (s).x, END_POINT (s).y);
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else
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{
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/* FATAL1 ("print_spline: strange degree (%d)", SPLINE_DEGREE (s)); */
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}
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}
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/* Evaluate the spline S at a given T value. This is an implementation
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of de Casteljau's algorithm. See Schneider's thesis (reference in
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../limn/README), p.37. The variable names are taken from there. */
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real_coordinate_type
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evaluate_spline (spline_type s, real t)
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{
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spline_type V[4]; /* We need degree+1 splines, but assert degree <= 3. */
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unsigned i, j;
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real one_minus_t = 1.0 - t;
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polynomial_degree degree = SPLINE_DEGREE (s);
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for (i = 0; i <= degree; i++)
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V[0].v[i] = s.v[i];
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for (j = 1; j <= degree; j++)
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for (i = 0; i <= degree - j; i++)
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{
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#if defined (__GNUC__)
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real_coordinate_type t1 = Pmult_scalar (V[j - 1].v[i], one_minus_t);
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real_coordinate_type t2 = Pmult_scalar (V[j - 1].v[i + 1], t);
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V[j].v[i] = Padd (t1, t2);
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#else
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/* HB: the above is really nice, but is there any other compiler
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* supporting this ??
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*/
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real_coordinate_type t1;
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real_coordinate_type t2;
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t1.x = V[j - 1].v[i].x * one_minus_t;
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t1.y = V[j - 1].v[i].y * one_minus_t;
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t2.x = V[j - 1].v[i + 1].x * t;
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t2.y = V[j - 1].v[i + 1].y * t;
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V[j].v[i].x = t1.x + t2.x;
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V[j].v[i].y = t1.y + t2.y;
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#endif
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}
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return V[degree].v[0];
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}
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/* Return a new, empty, spline list. */
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spline_list_type *
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new_spline_list (void)
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{
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spline_list_type *answer = g_new (spline_list_type, 1);
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SPLINE_LIST_DATA (*answer) = NULL;
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SPLINE_LIST_LENGTH (*answer) = 0;
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return answer;
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}
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/* Return a new spline list with SPLINE as the first element. */
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spline_list_type *
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init_spline_list (spline_type spline)
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{
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spline_list_type *answer = g_new (spline_list_type, 1);
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SPLINE_LIST_DATA (*answer) = g_new (spline_type, 1);
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SPLINE_LIST_ELT (*answer, 0) = spline;
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SPLINE_LIST_LENGTH (*answer) = 1;
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return answer;
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}
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/* Free the storage in a spline list. We don't have to free the
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elements, since they are arrays in automatic storage. And we don't
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want to free the list if it was empty. */
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void
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free_spline_list (spline_list_type *spline_list)
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{
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if (SPLINE_LIST_DATA (*spline_list) != NULL)
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safe_free ((address *) &(SPLINE_LIST_DATA (*spline_list)));
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}
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/* Append the spline S to the list SPLINE_LIST. */
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void
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append_spline (spline_list_type *l, spline_type s)
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{
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assert (l != NULL);
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SPLINE_LIST_LENGTH (*l)++;
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SPLINE_LIST_DATA (*l) = g_realloc (SPLINE_LIST_DATA (*l),
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SPLINE_LIST_LENGTH (*l) * sizeof (spline_type));
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LAST_SPLINE_LIST_ELT (*l) = s;
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}
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/* Tack the elements in the list S2 onto the end of S1.
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S2 is not changed. */
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void
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concat_spline_lists (spline_list_type *s1, spline_list_type s2)
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{
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unsigned this_spline;
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unsigned new_length;
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assert (s1 != NULL);
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new_length = SPLINE_LIST_LENGTH (*s1) + SPLINE_LIST_LENGTH (s2);
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SPLINE_LIST_DATA (*s1) = g_realloc(SPLINE_LIST_DATA (*s1),new_length * sizeof(spline_type));
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for (this_spline = 0; this_spline < SPLINE_LIST_LENGTH (s2); this_spline++)
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SPLINE_LIST_ELT (*s1, SPLINE_LIST_LENGTH (*s1)++)
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= SPLINE_LIST_ELT (s2, this_spline);
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}
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/* Return a new, empty, spline list array. */
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spline_list_array_type
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new_spline_list_array (void)
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{
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spline_list_array_type answer;
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SPLINE_LIST_ARRAY_DATA (answer) = NULL;
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SPLINE_LIST_ARRAY_LENGTH (answer) = 0;
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return answer;
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}
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/* Free the storage in a spline list array. We don't
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want to free the list if it is empty. */
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void
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free_spline_list_array (spline_list_array_type *spline_list_array)
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{
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unsigned this_list;
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for (this_list = 0;
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this_list < SPLINE_LIST_ARRAY_LENGTH (*spline_list_array);
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this_list++)
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free_spline_list (&SPLINE_LIST_ARRAY_ELT (*spline_list_array, this_list));
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if (SPLINE_LIST_ARRAY_DATA (*spline_list_array) != NULL)
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safe_free ((address *) &(SPLINE_LIST_ARRAY_DATA (*spline_list_array)));
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}
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/* Append the spline S to the list SPLINE_LIST_ARRAY. */
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void
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append_spline_list (spline_list_array_type *l, spline_list_type s)
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{
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SPLINE_LIST_ARRAY_LENGTH (*l)++;
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SPLINE_LIST_ARRAY_DATA (*l) = g_realloc(SPLINE_LIST_ARRAY_DATA (*l),(SPLINE_LIST_ARRAY_LENGTH (*l))*sizeof(spline_list_type));
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LAST_SPLINE_LIST_ARRAY_ELT (*l) = s;
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}
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