/* Libart_LGPL - library of basic graphic primitives
* Copyright (C) 1998 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 bezier paths */
#include "config.h"
#include "art_vpath_bpath.h"
#include <math.h>
#include "art_misc.h"
#include "art_bpath.h"
#include "art_vpath.h"
/* p must be allocated 2^level points. */
/* level must be >= 1 */
ArtPoint *
art_bezier_to_vec (gdouble x0, gdouble y0,
gdouble x1, gdouble y1,
gdouble x2, gdouble y2,
gdouble x3, gdouble y3,
ArtPoint *p,
gint level)
{
gdouble x_m, y_m;
if (level == 1) {
x_m = (x0 + 3 * (x1 + x2) + x3) * 0.125;
y_m = (y0 + 3 * (y1 + y2) + y3) * 0.125;
p->x = x_m;
p->y = y_m;
p++;
p->x = x3;
p->y = y3;
p++;
} else {
gdouble xa1, ya1;
gdouble xa2, ya2;
gdouble xb1, yb1;
gdouble xb2, yb2;
xa1 = (x0 + x1) * 0.5;
ya1 = (y0 + y1) * 0.5;
xa2 = (x0 + 2 * x1 + x2) * 0.25;
ya2 = (y0 + 2 * y1 + y2) * 0.25;
xb1 = (x1 + 2 * x2 + x3) * 0.25;
yb1 = (y1 + 2 * y2 + y3) * 0.25;
xb2 = (x2 + x3) * 0.5;
yb2 = (y2 + y3) * 0.5;
x_m = (xa2 + xb1) * 0.5;
y_m = (ya2 + yb1) * 0.5;
p = art_bezier_to_vec (x0, y0, xa1, ya1, xa2, ya2, x_m, y_m, p, level - 1);
p = art_bezier_to_vec (x_m, y_m, xb1, yb1, xb2, yb2, x3, y3, p, level - 1);
}
return p;
}
#define RENDER_LEVEL 4
#define RENDER_SIZE (1 << (RENDER_LEVEL))
/**
* art_vpath_render_bez: Render a bezier segment into the 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.
* @x0: X coordinate of starting bezier point.
* @y0: Y coordinate of starting bezier point.
* @x1: X coordinate of first bezier control point.
* @y1: Y coordinate of first bezier control point.
* @x2: X coordinate of second bezier control point.
* @y2: Y coordinate of second bezier control point.
* @x3: X coordinate of ending bezier point.
* @y3: Y coordinate of ending bezier point.
* @flatness: Flatness control.
*
* Renders a bezier segment into the vector path, reallocating and
* updating *@p_vpath and *@pn_vpath_max as necessary. *@pn_vpath is
* incremented by the number of vector points added.
*
* This step includes (@x0, @y0) but not (@x3, @y3).
*
* The @flatness argument guides the amount of subdivision. The Adobe
* PostScript reference manual defines flatness as the maximum
* deviation between the any point on the vpath approximation and the
* corresponding point on the "true" curve, and we follow this
* definition here. A value of 0.25 should ensure high quality for aa
* rendering.
**/
static void
art_vpath_render_bez (ArtVpath **p_vpath, gint *pn, gint *pn_max,
gdouble x0, gdouble y0,
gdouble x1, gdouble y1,
gdouble x2, gdouble y2,
gdouble x3, gdouble y3,
gdouble flatness)
{
gdouble x3_0, y3_0;
gdouble z3_0_dot;
gdouble z1_dot, z2_dot;
gdouble z1_perp, z2_perp;
gdouble max_perp_sq;
gdouble x_m, y_m;
gdouble xa1, ya1;
gdouble xa2, ya2;
gdouble xb1, yb1;
gdouble xb2, yb2;
/* It's possible to optimize this routine a fair amount.
First, once the _dot conditions are met, they will also be met in
all further subdivisions. So we might recurse to a different
routine that only checks the _perp conditions.
Second, the distance _should_ decrease according to fairly
predictable rules (a factor of 4 with each subdivision). So it might
be possible to note that the distance is within a factor of 4 of
acceptable, and subdivide once. But proving this might be hard.
Third, at the last subdivision, x_m and y_m can be computed more
expeditiously (as in the routine above).
Finally, if we were able to subdivide by, say 2 or 3, this would
allow considerably finer-grain control, i.e. fewer points for the
same flatness tolerance. This would speed things up downstream.
In any case, this routine is unlikely to be the bottleneck. It's
just that I have this undying quest for more speed...
*/
x3_0 = x3 - x0;
y3_0 = y3 - y0;
/* z3_0_dot is dist z0-z3 squared */
z3_0_dot = x3_0 * x3_0 + y3_0 * y3_0;
if (z3_0_dot < 0.001)
{
/* if start and end point are almost identical, the flatness tests
* don't work properly, so fall back on testing whether both of
* the other two control points are the same as the start point,
* too.
*/
if (hypot (x1 - x0, y1 - y0) < 0.001
&& hypot (x2 - x0, y2 - y0) < 0.001)
goto nosubdivide;
else
goto subdivide;
}
/* we can avoid subdivision if:
z1 has distance no more than flatness from the z0-z3 line
z1 is no more z0'ward than flatness past z0-z3
z1 is more z0'ward than z3'ward on the line traversing z0-z3
and correspondingly for z2 */
/* perp is distance from line, multiplied by dist z0-z3 */
max_perp_sq = flatness * flatness * z3_0_dot;
z1_perp = (y1 - y0) * x3_0 - (x1 - x0) * y3_0;
if (z1_perp * z1_perp > max_perp_sq)
goto subdivide;
z2_perp = (y3 - y2) * x3_0 - (x3 - x2) * y3_0;
if (z2_perp * z2_perp > max_perp_sq)
goto subdivide;
z1_dot = (x1 - x0) * x3_0 + (y1 - y0) * y3_0;
if (z1_dot < 0 && z1_dot * z1_dot > max_perp_sq)
goto subdivide;
z2_dot = (x3 - x2) * x3_0 + (y3 - y2) * y3_0;
if (z2_dot < 0 && z2_dot * z2_dot > max_perp_sq)
goto subdivide;
if (z1_dot + z1_dot > z3_0_dot)
goto subdivide;
if (z2_dot + z2_dot > z3_0_dot)
goto subdivide;
nosubdivide:
/* don't subdivide */
art_vpath_add_point (p_vpath, pn, pn_max,
ART_LINETO, x3, y3);
return;
subdivide:
xa1 = (x0 + x1) * 0.5;
ya1 = (y0 + y1) * 0.5;
xa2 = (x0 + 2 * x1 + x2) * 0.25;
ya2 = (y0 + 2 * y1 + y2) * 0.25;
xb1 = (x1 + 2 * x2 + x3) * 0.25;
yb1 = (y1 + 2 * y2 + y3) * 0.25;
xb2 = (x2 + x3) * 0.5;
yb2 = (y2 + y3) * 0.5;
x_m = (xa2 + xb1) * 0.5;
y_m = (ya2 + yb1) * 0.5;
art_vpath_render_bez (p_vpath, pn, pn_max,
x0, y0, xa1, ya1, xa2, ya2, x_m, y_m, flatness);
art_vpath_render_bez (p_vpath, pn, pn_max,
x_m, y_m, xb1, yb1, xb2, yb2, x3, y3, flatness);
}
/**
* art_bez_path_to_vec: Create vpath from bezier path.
* @bez: Bezier path.
* @flatness: Flatness control.
*
* Creates a vector path closely approximating the bezier path defined by
* @bez. The @flatness argument controls the amount of subdivision. In
* general, the resulting vpath deviates by at most @flatness pixels
* from the "ideal" path described by @bez.
*
* Return value: Newly allocated vpath.
**/
ArtVpath *
art_bez_path_to_vec (const ArtBpath *bez, gdouble flatness)
{
ArtVpath *vec;
gint vec_n, vec_n_max;
gint bez_index;
gdouble x, y;
vec_n = 0;
vec_n_max = RENDER_SIZE;
vec = art_new (ArtVpath, vec_n_max);
/* Initialization is unnecessary because of the precondition that the
bezier path does not begin with LINETO or CURVETO, but is here
to make the code warning-free. */
x = 0;
y = 0;
bez_index = 0;
do
{
/* make sure space for at least one more code */
if (vec_n >= vec_n_max)
art_expand (vec, ArtVpath, vec_n_max);
switch (bez[bez_index].code)
{
case ART_MOVETO_OPEN:
case ART_MOVETO:
case ART_LINETO:
x = bez[bez_index].x3;
y = bez[bez_index].y3;
vec[vec_n].code = bez[bez_index].code;
vec[vec_n].x = x;
vec[vec_n].y = y;
vec_n++;
break;
case ART_END:
vec[vec_n].code = bez[bez_index].code;
vec[vec_n].x = 0;
vec[vec_n].y = 0;
vec_n++;
break;
case ART_CURVETO:
art_vpath_render_bez (&vec, &vec_n, &vec_n_max,
x, y,
bez[bez_index].x1, bez[bez_index].y1,
bez[bez_index].x2, bez[bez_index].y2,
bez[bez_index].x3, bez[bez_index].y3,
flatness);
x = bez[bez_index].x3;
y = bez[bez_index].y3;
break;
}
}
while (bez[bez_index++].code != ART_END);
return vec;
}
