125 lines
4.1 KiB
C
125 lines
4.1 KiB
C
/* spline.h: manipulate the spline representation.
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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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#ifndef SPLINE_H
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#define SPLINE_H
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#include <stdio.h>
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#include "bounding-box.h"
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#include "types.h"
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/* Third degree is the highest we deal with. */
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typedef enum
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{
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LINEAR = 1, QUADRATIC = 2, CUBIC = 3
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} polynomial_degree;
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/* A Bezier spline can be represented as four points in the real plane:
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a starting point, ending point, and two control points. The
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curve always lies in the convex hull defined by the four points. It
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is also convenient to save the divergence of the spline from the
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straight line defined by the endpoints. */
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typedef struct
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{
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real_coordinate_type v[4]; /* The control points. */
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polynomial_degree degree;
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real linearity;
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} spline_type;
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#define START_POINT(spl) ((spl).v[0])
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#define CONTROL1(spl) ((spl).v[1])
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#define CONTROL2(spl) ((spl).v[2])
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#define END_POINT(spl) ((spl).v[3])
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#define SPLINE_DEGREE(spl) ((spl).degree)
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#define SPLINE_LINEARITY(spl) ((spl).linearity)
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/* Return a spline structure. */
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extern spline_type new_spline (void);
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/* Print a spline on the given file. */
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extern void print_spline (FILE *, spline_type);
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/* Evaluate SPLINE at the given T value. */
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extern real_coordinate_type evaluate_spline (spline_type spline, real t);
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/* Each outline in a character is typically represented by many
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splines. So, here is a list structure for that: */
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typedef struct
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{
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spline_type *data;
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unsigned length;
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} spline_list_type;
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/* An empty list will have length zero (and null data). */
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#define SPLINE_LIST_LENGTH(s_l) ((s_l).length)
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/* The address of the beginning of the array of data. */
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#define SPLINE_LIST_DATA(s_l) ((s_l).data)
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/* The element INDEX in S_L. */
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#define SPLINE_LIST_ELT(s_l, index) (SPLINE_LIST_DATA (s_l)[index])
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/* The last element in S_L. */
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#define LAST_SPLINE_LIST_ELT(s_l) \
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(SPLINE_LIST_DATA (s_l)[SPLINE_LIST_LENGTH (s_l) - 1])
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/* The previous and next elements to INDEX in S_L. */
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#define NEXT_SPLINE_LIST_ELT(s_l, index) \
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SPLINE_LIST_ELT (s_l, ((index) + 1) % SPLINE_LIST_LENGTH (s_l))
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#define PREV_SPLINE_LIST_ELT(s_l, index) \
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SPLINE_LIST_ELT (s_l, index == 0 \
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? SPLINE_LIST_LENGTH (s_l) - 1 \
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: index - 1)
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/* Construct and destroy new `spline_list_type' objects. */
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extern spline_list_type *new_spline_list (void);
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extern spline_list_type *init_spline_list (spline_type);
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extern void free_spline_list (spline_list_type *);
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/* Append the spline S to the list S_LIST. */
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extern void append_spline (spline_list_type *s_list, spline_type s);
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/* Append the elements in list S2 to S1, changing S1. */
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extern void concat_spline_lists (spline_list_type *s1, spline_list_type s2);
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/* Each character is in general made up of many outlines. So here is one
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more list structure. */
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typedef struct
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{
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spline_list_type *data;
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unsigned length;
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} spline_list_array_type;
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/* Turns out we can use the same definitions for lists of lists as for
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just lists. But we define the usual names, just in case. */
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#define SPLINE_LIST_ARRAY_LENGTH SPLINE_LIST_LENGTH
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#define SPLINE_LIST_ARRAY_DATA SPLINE_LIST_DATA
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#define SPLINE_LIST_ARRAY_ELT SPLINE_LIST_ELT
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#define LAST_SPLINE_LIST_ARRAY_ELT LAST_SPLINE_LIST_ELT
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/* The usual routines. */
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extern spline_list_array_type new_spline_list_array (void);
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extern void free_spline_list_array (spline_list_array_type *);
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extern void append_spline_list (spline_list_array_type *, spline_list_type);
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#endif /* not SPLINE_H */
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