mirror of https://github.com/GNOME/gimp.git
211 lines
8.1 KiB
C
211 lines
8.1 KiB
C
/* GIMP - The GNU Image Manipulation Program
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* Copyright (C) 1995 Spencer Kimball and Peter Mattis
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*
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* gimpcoords-interpolate.c
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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 2 of the License, or
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* (at your option) 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, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*/
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#include "config.h"
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#include <glib-object.h>
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#include "libgimpmath/gimpmath.h"
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#include "core-types.h"
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#include "gimpcoords.h"
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#include "gimpcoords-interpolate.h"
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/* Local helper functions declarations*/
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static void gimp_coords_interpolate_bezier_internal (const GimpCoords bezier_pt1,
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const GimpCoords bezier_pt2,
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const GimpCoords bezier_pt3,
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const GimpCoords bezier_pt4,
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const gdouble start_t,
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const gdouble end_t,
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const gdouble precision,
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GArray **ret_coords,
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GArray **ret_params,
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gint depth);
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/* Functions for bezier subdivision */
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void
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gimp_coords_interpolate_bezier (const GimpCoords bezier_pt1,
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const GimpCoords bezier_pt2,
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const GimpCoords bezier_pt3,
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const GimpCoords bezier_pt4,
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const gdouble precision,
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GArray **ret_coords,
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GArray **ret_params)
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{
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gimp_coords_interpolate_bezier_internal (bezier_pt1,
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bezier_pt2,
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bezier_pt3,
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bezier_pt4,
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0.0, 1.0,
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precision,
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ret_coords, ret_params, 10);
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}
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/* Recursive subdivision helper function */
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static void
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gimp_coords_interpolate_bezier_internal (const GimpCoords bezier_pt1,
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const GimpCoords bezier_pt2,
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const GimpCoords bezier_pt3,
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const GimpCoords bezier_pt4,
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const gdouble start_t,
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const gdouble end_t,
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const gdouble precision,
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GArray **ret_coords,
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GArray **ret_params,
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gint depth)
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{
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/*
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* beziercoords has to contain four GimpCoords with the four control points
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* of the bezier segment. We subdivide it at the parameter 0.5.
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*/
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GimpCoords subdivided[8];
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gdouble middle_t = (start_t + end_t) / 2;
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subdivided[0] = bezier_pt1;
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subdivided[6] = bezier_pt4;
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/* if (!depth) g_printerr ("Hit recursion depth limit!\n"); */
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gimp_coords_average (&bezier_pt1, &bezier_pt2, &(subdivided[1]));
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gimp_coords_average (&bezier_pt2, &bezier_pt3, &(subdivided[7]));
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gimp_coords_average (&bezier_pt3, &bezier_pt4, &(subdivided[5]));
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gimp_coords_average (&(subdivided[1]), &(subdivided[7]),
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&(subdivided[2]));
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gimp_coords_average (&(subdivided[7]), &(subdivided[5]),
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&(subdivided[4]));
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gimp_coords_average (&(subdivided[2]), &(subdivided[4]),
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&(subdivided[3]));
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/*
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* We now have the coordinates of the two bezier segments in
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* subdivided [0-3] and subdivided [3-6]
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*/
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/*
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* Here we need to check, if we have sufficiently subdivided, i.e.
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* if the stroke is sufficiently close to a straight line.
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*/
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if (!depth || gimp_coords_bezier_is_straight (subdivided[0],
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subdivided[1],
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subdivided[2],
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subdivided[3],
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precision)) /* 1st half */
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{
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*ret_coords = g_array_append_vals (*ret_coords, &(subdivided[0]), 3);
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if (ret_params)
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{
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gdouble params[3];
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params[0] = start_t;
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params[1] = (2 * start_t + middle_t) / 3;
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params[2] = (start_t + 2 * middle_t) / 3;
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*ret_params = g_array_append_vals (*ret_params, &(params[0]), 3);
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}
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}
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else
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{
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gimp_coords_interpolate_bezier_internal (subdivided[0],
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subdivided[1],
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subdivided[2],
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subdivided[3],
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start_t, (start_t + end_t) / 2,
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precision,
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ret_coords, ret_params, depth-1);
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}
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if (!depth || gimp_coords_bezier_is_straight (subdivided[3],
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subdivided[4],
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subdivided[5],
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subdivided[6],
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precision)) /* 2nd half */
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{
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*ret_coords = g_array_append_vals (*ret_coords, &(subdivided[3]), 3);
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if (ret_params)
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{
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gdouble params[3];
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params[0] = middle_t;
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params[1] = (2 * middle_t + end_t) / 3;
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params[2] = (middle_t + 2 * end_t) / 3;
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*ret_params = g_array_append_vals (*ret_params, &(params[0]), 3);
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}
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}
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else
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{
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gimp_coords_interpolate_bezier_internal (subdivided[3],
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subdivided[4],
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subdivided[5],
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subdivided[6],
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(start_t + end_t) / 2, end_t,
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precision,
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ret_coords, ret_params, depth-1);
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}
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}
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/*
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* a helper function that determines if a bezier segment is "straight
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* enough" to be approximated by a line.
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*
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* To be more exact, it also checks for the control points to be distributed
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* evenly along the line. This makes it easier to reconstruct parameters for
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* a given point along the segment.
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*
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* Needs four GimpCoords in an array.
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*/
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gboolean
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gimp_coords_bezier_is_straight (const GimpCoords bezier_pt1,
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const GimpCoords bezier_pt2,
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const GimpCoords bezier_pt3,
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const GimpCoords bezier_pt4,
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gdouble precision)
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{
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GimpCoords pt1, pt2;
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/* calculate the "ideal" positions for the control points */
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gimp_coords_mix (2.0 / 3.0, &bezier_pt1,
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1.0 / 3.0, &bezier_pt4,
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&pt1);
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gimp_coords_mix (1.0 / 3.0, &bezier_pt1,
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2.0 / 3.0, &bezier_pt4,
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&pt2);
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/* calculate the deviation of the actual control points */
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return (gimp_coords_manhattan_dist (&bezier_pt2, &pt1) < precision &&
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gimp_coords_manhattan_dist (&bezier_pt3, &pt2) < precision);
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}
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