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scummvm-cursorfix/engines/sword25/gfx/image/art.cpp
Leon Krieg 5b11698731 Initial commit
2026-02-02 04:50:13 +01:00

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/* ScummVM - Graphic Adventure Engine
*
* ScummVM is the legal property of its developers, whose names
* are too numerous to list here. Please refer to the COPYRIGHT
* file distributed with this source distribution.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
/*
* This code is based on Libart_LGPL - library of basic graphic primitives
*
* Copyright (c) 1998 Raph Levien
*
* Licensed under GNU LGPL v2
*
*/
/* Various utility functions RLL finds useful. */
#include "common/textconsole.h"
#include "math/utils.h"
#include "sword25/gfx/image/art.h"
namespace Sword25 {
/**
* art_svp_free: Free an #ArtSVP structure.
* @svp: #ArtSVP to free.
*
* Frees an #ArtSVP structure and all the segments in it.
**/
void art_svp_free(ArtSVP *svp) {
int n_segs = svp->n_segs;
int i;
for (i = 0; i < n_segs; i++)
free(svp->segs[i].points);
free(svp);
}
#define EPSILON 0
/**
* art_svp_seg_compare: Compare two segments of an svp.
* @seg1: First segment to compare.
* @seg2: Second segment to compare.
*
* Compares two segments of an svp. Return 1 if @seg2 is below or to the
* right of @seg1, -1 otherwise.
**/
int art_svp_seg_compare(const void *s1, const void *s2) {
const ArtSVPSeg *seg1 = (const ArtSVPSeg *)s1;
const ArtSVPSeg *seg2 = (const ArtSVPSeg *)s2;
if (seg1->points[0].y - EPSILON > seg2->points[0].y) return 1;
else if (seg1->points[0].y + EPSILON < seg2->points[0].y) return -1;
else if (seg1->points[0].x - EPSILON > seg2->points[0].x) return 1;
else if (seg1->points[0].x + EPSILON < seg2->points[0].x) return -1;
else if ((seg1->points[1].x - seg1->points[0].x) *
(seg2->points[1].y - seg2->points[0].y) -
(seg1->points[1].y - seg1->points[0].y) *
(seg2->points[1].x - seg2->points[0].x) > 0) return 1;
else return -1;
}
/**
* 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;
}
/* Sort vector paths into sorted vector paths */
/* reverse a list of points in place */
static void reverse_points(ArtPoint *points, int n_points) {
int i;
ArtPoint tmp_p;
for (i = 0; i < (n_points >> 1); i++) {
tmp_p = points[i];
points[i] = points[n_points - (i + 1)];
points[n_points - (i + 1)] = tmp_p;
}
}
/**
* art_svp_from_vpath: Convert a vpath to a sorted vector path.
* @vpath: #ArtVPath to convert.
*
* Converts a vector path into sorted vector path form. The svp form is
* more efficient for rendering and other vector operations.
*
* Basically, the implementation is to traverse the vector path,
* generating a new segment for each "run" of points in the vector
* path with monotonically increasing Y values. All the resulting
* values are then sorted.
*
* Note: I'm not sure that the sorting rule is correct with respect
* to numerical stability issues.
*
* Return value: Resulting sorted vector path.
**/
ArtSVP *art_svp_from_vpath(ArtVpath *vpath) {
int n_segs, n_segs_max;
ArtSVP *svp;
int dir;
int new_dir;
int i;
ArtPoint *points;
int n_points, n_points_max;
double x, y;
double x_min, x_max;
n_segs = 0;
n_segs_max = 16;
svp = (ArtSVP *)malloc(sizeof(ArtSVP) +
(n_segs_max - 1) * sizeof(ArtSVPSeg));
if (!svp)
error("[art_svp_from_vpath] Cannot allocate memory");
dir = 0;
n_points = 0;
n_points_max = 0;
points = NULL;
i = 0;
x = y = 0; /* unnecessary, given "first code must not be LINETO" invariant,
but it makes gcc -Wall -ansi -pedantic happier */
x_min = x_max = 0; /* same */
while (vpath[i].code != ART_END) {
if (vpath[i].code == ART_MOVETO || vpath[i].code == ART_MOVETO_OPEN) {
if (points != NULL && n_points >= 2) {
if (n_segs == n_segs_max) {
n_segs_max <<= 1;
ArtSVP *tmp = (ArtSVP *)realloc(svp, sizeof(ArtSVP) +
(n_segs_max - 1) *
sizeof(ArtSVPSeg));
if (!tmp)
error("Cannot reallocate memory in art_svp_from_vpath()");
svp = tmp;
}
svp->segs[n_segs].n_points = n_points;
svp->segs[n_segs].dir = (dir > 0);
if (dir < 0)
reverse_points(points, n_points);
svp->segs[n_segs].points = points;
svp->segs[n_segs].bbox.x0 = x_min;
svp->segs[n_segs].bbox.x1 = x_max;
svp->segs[n_segs].bbox.y0 = points[0].y;
svp->segs[n_segs].bbox.y1 = points[n_points - 1].y;
n_segs++;
points = NULL;
}
if (points == NULL) {
n_points_max = 4;
points = art_new(ArtPoint, n_points_max);
}
n_points = 1;
points[0].x = x = vpath[i].x;
points[0].y = y = vpath[i].y;
x_min = x;
x_max = x;
dir = 0;
} else { /* must be LINETO */
new_dir = (vpath[i].y > y ||
(vpath[i].y == y && vpath[i].x > x)) ? 1 : -1;
if (dir && dir != new_dir) {
/* new segment */
x = points[n_points - 1].x;
y = points[n_points - 1].y;
if (n_segs == n_segs_max) {
n_segs_max <<= 1;
ArtSVP *tmp = (ArtSVP *)realloc(svp, sizeof(ArtSVP) +
(n_segs_max - 1) *
sizeof(ArtSVPSeg));
if (!tmp)
error("Cannot reallocate memory in art_svp_from_vpath()");
svp = tmp;
}
svp->segs[n_segs].n_points = n_points;
svp->segs[n_segs].dir = (dir > 0);
if (dir < 0)
reverse_points(points, n_points);
svp->segs[n_segs].points = points;
svp->segs[n_segs].bbox.x0 = x_min;
svp->segs[n_segs].bbox.x1 = x_max;
svp->segs[n_segs].bbox.y0 = points[0].y;
svp->segs[n_segs].bbox.y1 = points[n_points - 1].y;
n_segs++;
n_points = 1;
n_points_max = 4;
points = art_new(ArtPoint, n_points_max);
points[0].x = x;
points[0].y = y;
x_min = x;
x_max = x;
}
if (points != NULL) {
if (n_points == n_points_max)
art_expand(points, ArtPoint, n_points_max);
points[n_points].x = x = vpath[i].x;
points[n_points].y = y = vpath[i].y;
if (x < x_min) x_min = x;
else if (x > x_max) x_max = x;
n_points++;
}
dir = new_dir;
}
i++;
}
if (points != NULL) {
if (n_points >= 2) {
if (n_segs == n_segs_max) {
n_segs_max <<= 1;
ArtSVP *tmp = (ArtSVP *)realloc(svp, sizeof(ArtSVP) +
(n_segs_max - 1) *
sizeof(ArtSVPSeg));
if (!tmp)
error("Cannot reallocate memory in art_svp_from_vpath()");
svp = tmp;
}
svp->segs[n_segs].n_points = n_points;
svp->segs[n_segs].dir = (dir > 0);
if (dir < 0)
reverse_points(points, n_points);
svp->segs[n_segs].points = points;
svp->segs[n_segs].bbox.x0 = x_min;
svp->segs[n_segs].bbox.x1 = x_max;
svp->segs[n_segs].bbox.y0 = points[0].y;
svp->segs[n_segs].bbox.y1 = points[n_points - 1].y;
n_segs++;
} else
free(points);
}
svp->n_segs = n_segs;
qsort(&svp->segs, n_segs, sizeof(ArtSVPSeg), art_svp_seg_compare);
return svp;
}
/* Basic constructors and operations for bezier paths */
#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, int *pn, int *pn_max,
double x0, double y0,
double x1, double y1,
double x2, double y2,
double x3, double y3,
double flatness) {
/* 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...
*/
bool subDivide = false;
double x3_0 = x3 - x0;
double y3_0 = y3 - y0;
// z3_0_dot is dist z0-z3 squared
double 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 (!(Math::hypotenuse(x1 - x0, y1 - y0) < 0.001
&& Math::hypotenuse(x2 - x0, y2 - y0) < 0.001))
subDivide = true;
} else {
/* 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
double max_perp_sq = flatness * flatness * z3_0_dot;
double z1_perp = (y1 - y0) * x3_0 - (x1 - x0) * y3_0;
if (z1_perp * z1_perp > max_perp_sq) {
subDivide = true;
} else {
double z2_perp = (y3 - y2) * x3_0 - (x3 - x2) * y3_0;
if (z2_perp * z2_perp > max_perp_sq) {
subDivide = true;
} else {
double z1_dot = (x1 - x0) * x3_0 + (y1 - y0) * y3_0;
if (z1_dot < 0 && z1_dot * z1_dot > max_perp_sq) {
subDivide = true;
} else {
double z2_dot = (x3 - x2) * x3_0 + (y3 - y2) * y3_0;
if (z2_dot < 0 && z2_dot * z2_dot > max_perp_sq)
subDivide = true;
else if (z1_dot + z1_dot > z3_0_dot)
subDivide = true;
else if (z2_dot + z2_dot > z3_0_dot)
subDivide = true;
}
}
}
}
if (subDivide) {
double xa1 = (x0 + x1) * 0.5;
double ya1 = (y0 + y1) * 0.5;
double xa2 = (x0 + 2 * x1 + x2) * 0.25;
double ya2 = (y0 + 2 * y1 + y2) * 0.25;
double xb1 = (x1 + 2 * x2 + x3) * 0.25;
double yb1 = (y1 + 2 * y2 + y3) * 0.25;
double xb2 = (x2 + x3) * 0.5;
double yb2 = (y2 + y3) * 0.5;
double x_m = (xa2 + xb1) * 0.5;
double 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);
} else {
// don't subdivide
art_vpath_add_point(p_vpath, pn, pn_max, ART_LINETO, x3, y3);
}
}
/**
* 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, double flatness) {
ArtVpath *vec;
int vec_n, vec_n_max;
int bez_index;
double 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;
default:
break;
}
} while (bez[bez_index++].code != ART_END);
return vec;
}
#define EPSILON_6 1e-6
#define EPSILON_2 1e-12
/* Render an arc segment starting at (xc + x0, yc + y0) to (xc + x1,
yc + y1), centered at (xc, yc), and with given radius. Both x0^2 +
y0^2 and x1^2 + y1^2 should be equal to radius^2.
A positive value of radius means curve to the left, negative means
curve to the right.
*/
static void art_svp_vpath_stroke_arc(ArtVpath **p_vpath, int *pn, int *pn_max,
double xc, double yc,
double x0, double y0,
double x1, double y1,
double radius,
double flatness) {
double theta;
double th_0, th_1;
int n_pts;
int i;
double aradius;
aradius = fabs(radius);
theta = 2 * M_SQRT2 * sqrt(flatness / aradius);
th_0 = atan2(y0, x0);
th_1 = atan2(y1, x1);
if (radius > 0) {
/* curve to the left */
if (th_0 < th_1) th_0 += M_PI * 2;
n_pts = (int)ceil((th_0 - th_1) / theta);
} else {
/* curve to the right */
if (th_1 < th_0) th_1 += M_PI * 2;
n_pts = (int)ceil((th_1 - th_0) / theta);
}
art_vpath_add_point(p_vpath, pn, pn_max,
ART_LINETO, xc + x0, yc + y0);
for (i = 1; i < n_pts; i++) {
theta = th_0 + (th_1 - th_0) * i / n_pts;
art_vpath_add_point(p_vpath, pn, pn_max,
ART_LINETO, xc + cos(theta) * aradius,
yc + sin(theta) * aradius);
}
art_vpath_add_point(p_vpath, pn, pn_max,
ART_LINETO, xc + x1, yc + y1);
}
/* Assume that forw and rev are at point i0. Bring them to i1,
joining with the vector i1 - i2.
This used to be true, but isn't now that the stroke_raw code is
filtering out (near)zero length vectors: {It so happens that all
invocations of this function maintain the precondition i1 = i0 + 1,
so we could decrease the number of arguments by one. We haven't
done that here, though.}
forw is to the line's right and rev is to its left.
Precondition: no zero-length vectors, otherwise a divide by
zero will happen. */
static void render_seg(ArtVpath **p_forw, int *pn_forw, int *pn_forw_max,
ArtVpath **p_rev, int *pn_rev, int *pn_rev_max,
ArtVpath *vpath, int i0, int i1, int i2,
ArtPathStrokeJoinType join,
double line_width, double miter_limit, double flatness) {
double dx0, dy0;
double dx1, dy1;
double dlx0, dly0;
double dlx1, dly1;
double dmx, dmy;
double dmr2;
double scale;
double cross;
/* The vectors of the lines from i0 to i1 and i1 to i2. */
dx0 = vpath[i1].x - vpath[i0].x;
dy0 = vpath[i1].y - vpath[i0].y;
dx1 = vpath[i2].x - vpath[i1].x;
dy1 = vpath[i2].y - vpath[i1].y;
/* Set dl[xy]0 to the vector from i0 to i1, rotated counterclockwise
90 degrees, and scaled to the length of line_width. */
scale = line_width / sqrt(dx0 * dx0 + dy0 * dy0);
dlx0 = dy0 * scale;
dly0 = -dx0 * scale;
/* Set dl[xy]1 to the vector from i1 to i2, rotated counterclockwise
90 degrees, and scaled to the length of line_width. */
scale = line_width / sqrt(dx1 * dx1 + dy1 * dy1);
dlx1 = dy1 * scale;
dly1 = -dx1 * scale;
/* now, forw's last point is expected to be colinear along d[xy]0
to point i0 - dl[xy]0, and rev with i0 + dl[xy]0. */
/* positive for positive area (i.e. left turn) */
cross = dx1 * dy0 - dx0 * dy1;
dmx = (dlx0 + dlx1) * 0.5;
dmy = (dly0 + dly1) * 0.5;
dmr2 = dmx * dmx + dmy * dmy;
if (join == ART_PATH_STROKE_JOIN_MITER &&
dmr2 * miter_limit * miter_limit < line_width * line_width)
join = ART_PATH_STROKE_JOIN_BEVEL;
/* the case when dmr2 is zero or very small bothers me
(i.e. near a 180 degree angle)
ALEX: So, we avoid the optimization when dmr2 is very small. This should
be safe since dmx/y is only used in optimization and in MITER case, and MITER
should be converted to BEVEL when dmr2 is very small. */
if (dmr2 > EPSILON_2) {
scale = line_width * line_width / dmr2;
dmx *= scale;
dmy *= scale;
}
if (cross *cross < EPSILON_2 && dx0 *dx1 + dy0 *dy1 >= 0) {
/* going straight */
art_vpath_add_point(p_forw, pn_forw, pn_forw_max,
ART_LINETO, vpath[i1].x - dlx0, vpath[i1].y - dly0);
art_vpath_add_point(p_rev, pn_rev, pn_rev_max,
ART_LINETO, vpath[i1].x + dlx0, vpath[i1].y + dly0);
} else if (cross > 0) {
/* left turn, forw is outside and rev is inside */
if (
(dmr2 > EPSILON_2) &&
/* check that i1 + dm[xy] is inside i0-i1 rectangle */
(dx0 + dmx) * dx0 + (dy0 + dmy) * dy0 > 0 &&
/* and that i1 + dm[xy] is inside i1-i2 rectangle */
((dx1 - dmx) * dx1 + (dy1 - dmy) * dy1 > 0)
#ifdef PEDANTIC_INNER
&&
/* check that i1 + dl[xy]1 is inside i0-i1 rectangle */
(dx0 + dlx1) * dx0 + (dy0 + dly1) * dy0 > 0 &&
/* and that i1 + dl[xy]0 is inside i1-i2 rectangle */
((dx1 - dlx0) * dx1 + (dy1 - dly0) * dy1 > 0)
#endif
) {
/* can safely add single intersection point */
art_vpath_add_point(p_rev, pn_rev, pn_rev_max,
ART_LINETO, vpath[i1].x + dmx, vpath[i1].y + dmy);
} else {
/* need to loop-de-loop the inside */
art_vpath_add_point(p_rev, pn_rev, pn_rev_max,
ART_LINETO, vpath[i1].x + dlx0, vpath[i1].y + dly0);
art_vpath_add_point(p_rev, pn_rev, pn_rev_max,
ART_LINETO, vpath[i1].x, vpath[i1].y);
art_vpath_add_point(p_rev, pn_rev, pn_rev_max,
ART_LINETO, vpath[i1].x + dlx1, vpath[i1].y + dly1);
}
if (join == ART_PATH_STROKE_JOIN_BEVEL) {
/* bevel */
art_vpath_add_point(p_forw, pn_forw, pn_forw_max,
ART_LINETO, vpath[i1].x - dlx0, vpath[i1].y - dly0);
art_vpath_add_point(p_forw, pn_forw, pn_forw_max,
ART_LINETO, vpath[i1].x - dlx1, vpath[i1].y - dly1);
} else if (join == ART_PATH_STROKE_JOIN_MITER) {
art_vpath_add_point(p_forw, pn_forw, pn_forw_max,
ART_LINETO, vpath[i1].x - dmx, vpath[i1].y - dmy);
} else if (join == ART_PATH_STROKE_JOIN_ROUND)
art_svp_vpath_stroke_arc(p_forw, pn_forw, pn_forw_max,
vpath[i1].x, vpath[i1].y,
-dlx0, -dly0,
-dlx1, -dly1,
line_width,
flatness);
} else {
/* right turn, rev is outside and forw is inside */
if (
(dmr2 > EPSILON_2) &&
/* check that i1 - dm[xy] is inside i0-i1 rectangle */
(dx0 - dmx) * dx0 + (dy0 - dmy) * dy0 > 0 &&
/* and that i1 - dm[xy] is inside i1-i2 rectangle */
((dx1 + dmx) * dx1 + (dy1 + dmy) * dy1 > 0)
#ifdef PEDANTIC_INNER
&&
/* check that i1 - dl[xy]1 is inside i0-i1 rectangle */
(dx0 - dlx1) * dx0 + (dy0 - dly1) * dy0 > 0 &&
/* and that i1 - dl[xy]0 is inside i1-i2 rectangle */
((dx1 + dlx0) * dx1 + (dy1 + dly0) * dy1 > 0)
#endif
) {
/* can safely add single intersection point */
art_vpath_add_point(p_forw, pn_forw, pn_forw_max,
ART_LINETO, vpath[i1].x - dmx, vpath[i1].y - dmy);
} else {
/* need to loop-de-loop the inside */
art_vpath_add_point(p_forw, pn_forw, pn_forw_max,
ART_LINETO, vpath[i1].x - dlx0, vpath[i1].y - dly0);
art_vpath_add_point(p_forw, pn_forw, pn_forw_max,
ART_LINETO, vpath[i1].x, vpath[i1].y);
art_vpath_add_point(p_forw, pn_forw, pn_forw_max,
ART_LINETO, vpath[i1].x - dlx1, vpath[i1].y - dly1);
}
if (join == ART_PATH_STROKE_JOIN_BEVEL) {
/* bevel */
art_vpath_add_point(p_rev, pn_rev, pn_rev_max,
ART_LINETO, vpath[i1].x + dlx0, vpath[i1].y + dly0);
art_vpath_add_point(p_rev, pn_rev, pn_rev_max,
ART_LINETO, vpath[i1].x + dlx1, vpath[i1].y + dly1);
} else if (join == ART_PATH_STROKE_JOIN_MITER) {
art_vpath_add_point(p_rev, pn_rev, pn_rev_max,
ART_LINETO, vpath[i1].x + dmx, vpath[i1].y + dmy);
} else if (join == ART_PATH_STROKE_JOIN_ROUND)
art_svp_vpath_stroke_arc(p_rev, pn_rev, pn_rev_max,
vpath[i1].x, vpath[i1].y,
dlx0, dly0,
dlx1, dly1,
-line_width,
flatness);
}
}
/* caps i1, under the assumption of a vector from i0 */
static void render_cap(ArtVpath **p_result, int *pn_result, int *pn_result_max,
ArtVpath *vpath, int i0, int i1,
ArtPathStrokeCapType cap, double line_width, double flatness) {
double dx0, dy0;
double dlx0, dly0;
double scale;
int n_pts;
int i;
dx0 = vpath[i1].x - vpath[i0].x;
dy0 = vpath[i1].y - vpath[i0].y;
/* Set dl[xy]0 to the vector from i0 to i1, rotated counterclockwise
90 degrees, and scaled to the length of line_width. */
scale = line_width / sqrt(dx0 * dx0 + dy0 * dy0);
dlx0 = dy0 * scale;
dly0 = -dx0 * scale;
switch (cap) {
case ART_PATH_STROKE_CAP_BUTT:
art_vpath_add_point(p_result, pn_result, pn_result_max,
ART_LINETO, vpath[i1].x - dlx0, vpath[i1].y - dly0);
art_vpath_add_point(p_result, pn_result, pn_result_max,
ART_LINETO, vpath[i1].x + dlx0, vpath[i1].y + dly0);
break;
case ART_PATH_STROKE_CAP_ROUND:
n_pts = (int)ceil(M_PI / (2.0 * M_SQRT2 * sqrt(flatness / line_width)));
art_vpath_add_point(p_result, pn_result, pn_result_max,
ART_LINETO, vpath[i1].x - dlx0, vpath[i1].y - dly0);
for (i = 1; i < n_pts; i++) {
double theta, c_th, s_th;
theta = M_PI * i / n_pts;
c_th = cos(theta);
s_th = sin(theta);
art_vpath_add_point(p_result, pn_result, pn_result_max,
ART_LINETO,
vpath[i1].x - dlx0 * c_th - dly0 * s_th,
vpath[i1].y - dly0 * c_th + dlx0 * s_th);
}
art_vpath_add_point(p_result, pn_result, pn_result_max,
ART_LINETO, vpath[i1].x + dlx0, vpath[i1].y + dly0);
break;
case ART_PATH_STROKE_CAP_SQUARE:
art_vpath_add_point(p_result, pn_result, pn_result_max,
ART_LINETO,
vpath[i1].x - dlx0 - dly0,
vpath[i1].y - dly0 + dlx0);
art_vpath_add_point(p_result, pn_result, pn_result_max,
ART_LINETO,
vpath[i1].x + dlx0 - dly0,
vpath[i1].y + dly0 + dlx0);
break;
default:
break;
}
}
/**
* art_svp_from_vpath_raw: Stroke a vector path, raw version
* @vpath: #ArtVPath to stroke.
* @join: Join style.
* @cap: Cap style.
* @line_width: Width of stroke.
* @miter_limit: Miter limit.
* @flatness: Flatness.
*
* Exactly the same as art_svp_vpath_stroke(), except that the resulting
* stroke outline may self-intersect and have regions of winding number
* greater than 1.
*
* Return value: Resulting raw stroked outline in svp format.
**/
ArtVpath *art_svp_vpath_stroke_raw(ArtVpath *vpath,
ArtPathStrokeJoinType join,
ArtPathStrokeCapType cap,
double line_width,
double miter_limit,
double flatness) {
int begin_idx, end_idx;
int i;
ArtVpath *forw, *rev;
int n_forw, n_rev;
int n_forw_max, n_rev_max;
ArtVpath *result;
int n_result, n_result_max;
double half_lw = 0.5 * line_width;
int closed;
int last, this_, next, second;
double dx, dy;
n_forw_max = 16;
forw = art_new(ArtVpath, n_forw_max);
n_rev_max = 16;
rev = art_new(ArtVpath, n_rev_max);
n_result = 0;
n_result_max = 16;
result = art_new(ArtVpath, n_result_max);
for (begin_idx = 0; vpath[begin_idx].code != ART_END; begin_idx = end_idx) {
n_forw = 0;
n_rev = 0;
closed = (vpath[begin_idx].code == ART_MOVETO);
/* we don't know what the first point joins with until we get to the
last point and see if it's closed. So we start with the second
line in the path.
Note: this is not strictly true (we now know it's closed from
the opening pathcode), but why fix code that isn't broken?
*/
this_ = begin_idx;
/* skip over identical points at the beginning of the subpath */
for (i = this_ + 1; vpath[i].code == ART_LINETO; i++) {
dx = vpath[i].x - vpath[this_].x;
dy = vpath[i].y - vpath[this_].y;
if (dx * dx + dy * dy > EPSILON_2)
break;
}
next = i;
second = next;
/* invariant: this doesn't coincide with next */
while (vpath[next].code == ART_LINETO) {
last = this_;
this_ = next;
/* skip over identical points after the beginning of the subpath */
for (i = this_ + 1; vpath[i].code == ART_LINETO; i++) {
dx = vpath[i].x - vpath[this_].x;
dy = vpath[i].y - vpath[this_].y;
if (dx * dx + dy * dy > EPSILON_2)
break;
}
next = i;
if (vpath[next].code != ART_LINETO) {
/* reached end of path */
/* make "closed" detection conform to PostScript
semantics (i.e. explicit closepath code rather than
just the fact that end of the path is the beginning) */
if (closed &&
vpath[this_].x == vpath[begin_idx].x &&
vpath[this_].y == vpath[begin_idx].y) {
int j;
/* path is closed, render join to beginning */
render_seg(&forw, &n_forw, &n_forw_max,
&rev, &n_rev, &n_rev_max,
vpath, last, this_, second,
join, half_lw, miter_limit, flatness);
/* do forward path */
art_vpath_add_point(&result, &n_result, &n_result_max,
ART_MOVETO, forw[n_forw - 1].x,
forw[n_forw - 1].y);
for (j = 0; j < n_forw; j++)
art_vpath_add_point(&result, &n_result, &n_result_max,
ART_LINETO, forw[j].x,
forw[j].y);
/* do reverse path, reversed */
art_vpath_add_point(&result, &n_result, &n_result_max,
ART_MOVETO, rev[0].x,
rev[0].y);
for (j = n_rev - 1; j >= 0; j--)
art_vpath_add_point(&result, &n_result, &n_result_max,
ART_LINETO, rev[j].x,
rev[j].y);
} else {
/* path is open */
int j;
/* add to forw rather than result to ensure that
forw has at least one point. */
render_cap(&forw, &n_forw, &n_forw_max,
vpath, last, this_,
cap, half_lw, flatness);
art_vpath_add_point(&result, &n_result, &n_result_max,
ART_MOVETO, forw[0].x,
forw[0].y);
for (j = 1; j < n_forw; j++)
art_vpath_add_point(&result, &n_result, &n_result_max,
ART_LINETO, forw[j].x,
forw[j].y);
for (j = n_rev - 1; j >= 0; j--)
art_vpath_add_point(&result, &n_result, &n_result_max,
ART_LINETO, rev[j].x,
rev[j].y);
render_cap(&result, &n_result, &n_result_max,
vpath, second, begin_idx,
cap, half_lw, flatness);
art_vpath_add_point(&result, &n_result, &n_result_max,
ART_LINETO, forw[0].x,
forw[0].y);
}
} else
render_seg(&forw, &n_forw, &n_forw_max,
&rev, &n_rev, &n_rev_max,
vpath, last, this_, next,
join, half_lw, miter_limit, flatness);
}
end_idx = next;
}
free(forw);
free(rev);
art_vpath_add_point(&result, &n_result, &n_result_max, ART_END, 0, 0);
return result;
}
/* Render a vector path into a stroked outline.
Status of this routine:
Basic correctness: Only miter and bevel line joins are implemented,
and only butt line caps. Otherwise, seems to be fine.
Numerical stability: We cheat (adding random perturbation). Thus,
it seems very likely that no numerical stability problems will be
seen in practice.
Speed: Should be pretty good.
Precision: The perturbation fuzzes the coordinates slightly,
but not enough to be visible. */
/**
* art_svp_vpath_stroke: Stroke a vector path.
* @vpath: #ArtVPath to stroke.
* @join: Join style.
* @cap: Cap style.
* @line_width: Width of stroke.
* @miter_limit: Miter limit.
* @flatness: Flatness.
*
* Computes an svp representing the stroked outline of @vpath. The
* width of the stroked line is @line_width.
*
* Lines are joined according to the @join rule. Possible values are
* ART_PATH_STROKE_JOIN_MITER (for mitered joins),
* ART_PATH_STROKE_JOIN_ROUND (for round joins), and
* ART_PATH_STROKE_JOIN_BEVEL (for bevelled joins). The mitered join
* is converted to a bevelled join if the miter would extend to a
* distance of more than @miter_limit * @line_width from the actual
* join point.
*
* If there are open subpaths, the ends of these subpaths are capped
* according to the @cap rule. Possible values are
* ART_PATH_STROKE_CAP_BUTT (squared cap, extends exactly to end
* point), ART_PATH_STROKE_CAP_ROUND (rounded half-circle centered at
* the end point), and ART_PATH_STROKE_CAP_SQUARE (squared cap,
* extending half @line_width past the end point).
*
* The @flatness parameter controls the accuracy of the rendering. It
* is most important for determining the number of points to use to
* approximate circular arcs for round lines and joins. In general, the
* resulting vector path will be within @flatness pixels of the "ideal"
* path containing actual circular arcs. I reserve the right to use
* the @flatness parameter to convert bevelled joins to miters for very
* small turn angles, as this would reduce the number of points in the
* resulting outline path.
*
* The resulting path is "clean" with respect to self-intersections, i.e.
* the winding number is 0 or 1 at each point.
*
* Return value: Resulting stroked outline in svp format.
**/
ArtSVP *art_svp_vpath_stroke(ArtVpath *vpath,
ArtPathStrokeJoinType join,
ArtPathStrokeCapType cap,
double line_width,
double miter_limit,
double flatness) {
ArtVpath *vpath_stroke;
ArtSVP *svp, *svp2;
ArtSvpWriter *swr;
vpath_stroke = art_svp_vpath_stroke_raw(vpath, join, cap,
line_width, miter_limit, flatness);
svp = art_svp_from_vpath(vpath_stroke);
free(vpath_stroke);
swr = art_svp_writer_rewind_new(ART_WIND_RULE_NONZERO);
art_svp_intersector(svp, swr);
svp2 = art_svp_writer_rewind_reap(swr);
art_svp_free(svp);
return svp2;
}
/* Testbed implementation of the new intersection code.
*/
typedef struct _ArtPriQ ArtPriQ;
typedef struct _ArtPriPoint ArtPriPoint;
struct _ArtPriQ {
int n_items;
int n_items_max;
ArtPriPoint **items;
};
struct _ArtPriPoint {
double x;
double y;
void *user_data;
};
static ArtPriQ *art_pri_new(void) {
ArtPriQ *result = art_new(ArtPriQ, 1);
if (!result)
error("[art_pri_new] Cannot allocate memory");
result->n_items = 0;
result->n_items_max = 16;
result->items = art_new(ArtPriPoint *, result->n_items_max);
return result;
}
static void art_pri_free(ArtPriQ *pq) {
free(pq->items);
free(pq);
}
static bool art_pri_empty(ArtPriQ *pq) {
return pq->n_items == 0;
}
/* This heap implementation is based on Vasek Chvatal's course notes:
https://users.encs.concordia.ca/~chvatal/notes/pq.html#heap */
static void art_pri_bubble_up(ArtPriQ *pq, int vacant, ArtPriPoint *missing) {
ArtPriPoint **items = pq->items;
int parent;
parent = (vacant - 1) >> 1;
while (vacant > 0 && (missing->y < items[parent]->y ||
(missing->y == items[parent]->y &&
missing->x < items[parent]->x))) {
items[vacant] = items[parent];
vacant = parent;
parent = (vacant - 1) >> 1;
}
items[vacant] = missing;
}
static void art_pri_insert(ArtPriQ *pq, ArtPriPoint *point) {
if (pq->n_items == pq->n_items_max)
art_expand(pq->items, ArtPriPoint *, pq->n_items_max);
art_pri_bubble_up(pq, pq->n_items++, point);
}
static void art_pri_sift_down_from_root(ArtPriQ *pq, ArtPriPoint *missing) {
ArtPriPoint **items = pq->items;
int vacant = 0, child = 2;
int n = pq->n_items;
while (child < n) {
if (items[child - 1]->y < items[child]->y ||
(items[child - 1]->y == items[child]->y &&
items[child - 1]->x < items[child]->x))
child--;
items[vacant] = items[child];
vacant = child;
child = (vacant + 1) << 1;
}
if (child == n) {
items[vacant] = items[n - 1];
vacant = n - 1;
}
art_pri_bubble_up(pq, vacant, missing);
}
static ArtPriPoint *art_pri_choose(ArtPriQ *pq) {
ArtPriPoint *result = pq->items[0];
art_pri_sift_down_from_root(pq, pq->items[--pq->n_items]);
return result;
}
/* A virtual class for an "svp writer". A client of this object creates an
SVP by repeatedly calling "add segment" and "add point" methods on it.
*/
typedef struct _ArtSvpWriterRewind ArtSvpWriterRewind;
/* An implementation of the svp writer virtual class that applies the
winding rule. */
struct _ArtSvpWriterRewind {
ArtSvpWriter super;
ArtWindRule rule;
ArtSVP *svp;
int n_segs_max;
int *n_points_max;
};
static int art_svp_writer_rewind_add_segment(ArtSvpWriter *self, int wind_left,
int delta_wind, double x, double y) {
ArtSvpWriterRewind *swr = (ArtSvpWriterRewind *)self;
ArtSVP *svp;
ArtSVPSeg *seg;
bool left_filled = 0, right_filled = 0;
int wind_right = wind_left + delta_wind;
int seg_num;
const int init_n_points_max = 4;
switch (swr->rule) {
case ART_WIND_RULE_NONZERO:
left_filled = (wind_left != 0);
right_filled = (wind_right != 0);
break;
case ART_WIND_RULE_INTERSECT:
left_filled = (wind_left > 1);
right_filled = (wind_right > 1);
break;
case ART_WIND_RULE_ODDEVEN:
left_filled = (wind_left & 1);
right_filled = (wind_right & 1);
break;
case ART_WIND_RULE_POSITIVE:
left_filled = (wind_left > 0);
right_filled = (wind_right > 0);
break;
default:
error("Unknown wind rule %d", swr->rule);
}
if (left_filled == right_filled) {
/* discard segment now */
return -1;
}
svp = swr->svp;
seg_num = svp->n_segs++;
if (swr->n_segs_max == seg_num) {
swr->n_segs_max <<= 1;
svp = (ArtSVP *)realloc(svp, sizeof(ArtSVP) +
(swr->n_segs_max - 1) *
sizeof(ArtSVPSeg));
swr->svp = svp;
int *tmp = art_renew(swr->n_points_max, int,
swr->n_segs_max);
if (!tmp)
error("Cannot reallocate memory in art_svp_writer_rewind_add_segment()");
swr->n_points_max = tmp;
}
seg = &svp->segs[seg_num];
seg->n_points = 1;
seg->dir = right_filled;
swr->n_points_max[seg_num] = init_n_points_max;
seg->bbox.x0 = x;
seg->bbox.y0 = y;
seg->bbox.x1 = x;
seg->bbox.y1 = y;
seg->points = art_new(ArtPoint, init_n_points_max);
if (!seg->points)
error("[art_svp_writer_rewind_add_segment] Cannot allocate memory");
seg->points[0].x = x;
seg->points[0].y = y;
return seg_num;
}
static void art_svp_writer_rewind_add_point(ArtSvpWriter *self, int seg_id,
double x, double y) {
ArtSvpWriterRewind *swr = (ArtSvpWriterRewind *)self;
ArtSVPSeg *seg;
int n_points;
if (seg_id < 0)
/* omitted segment */
return;
seg = &swr->svp->segs[seg_id];
n_points = seg->n_points++;
if (swr->n_points_max[seg_id] == n_points)
art_expand(seg->points, ArtPoint, swr->n_points_max[seg_id]);
seg->points[n_points].x = x;
seg->points[n_points].y = y;
if (x < seg->bbox.x0)
seg->bbox.x0 = x;
if (x > seg->bbox.x1)
seg->bbox.x1 = x;
seg->bbox.y1 = y;
}
static void art_svp_writer_rewind_close_segment(ArtSvpWriter *self, int seg_id) {
/* Not needed for this simple implementation. A potential future
optimization is to merge segments that can be merged safely. */
}
ArtSVP *art_svp_writer_rewind_reap(ArtSvpWriter *self) {
ArtSvpWriterRewind *swr = (ArtSvpWriterRewind *)self;
ArtSVP *result = swr->svp;
free(swr->n_points_max);
free(swr);
return result;
}
ArtSvpWriter *art_svp_writer_rewind_new(ArtWindRule rule) {
ArtSvpWriterRewind *result = art_new(ArtSvpWriterRewind, 1);
if (!result)
error("[art_svp_writer_rewind_new] Cannot allocate memory");
result->super.add_segment = art_svp_writer_rewind_add_segment;
result->super.add_point = art_svp_writer_rewind_add_point;
result->super.close_segment = art_svp_writer_rewind_close_segment;
result->rule = rule;
result->n_segs_max = 16;
result->svp = (ArtSVP *)malloc(sizeof(ArtSVP) +
(result->n_segs_max - 1) * sizeof(ArtSVPSeg));
if (!result->svp)
error("[art_svp_writer_rewind_new] Cannot allocate memory");
result->svp->n_segs = 0;
result->n_points_max = art_new(int, result->n_segs_max);
return &result->super;
}
/* Now, data structures for the active list */
typedef struct _ArtActiveSeg ArtActiveSeg;
/* Note: BNEG is 1 for \ lines, and 0 for /. Thus,
x[(flags & BNEG) ^ 1] <= x[flags & BNEG] */
#define ART_ACTIVE_FLAGS_BNEG 1
/* This flag is set if the segment has been inserted into the active
list. */
#define ART_ACTIVE_FLAGS_IN_ACTIVE 2
/* This flag is set when the segment is to be deleted in the
horiz commit process. */
#define ART_ACTIVE_FLAGS_DEL 4
/* This flag is set if the seg_id is a valid output segment. */
#define ART_ACTIVE_FLAGS_OUT 8
/* This flag is set if the segment is in the horiz list. */
#define ART_ACTIVE_FLAGS_IN_HORIZ 16
struct _ArtActiveSeg {
int flags;
int wind_left, delta_wind;
ArtActiveSeg *left, *right; /* doubly linked list structure */
const ArtSVPSeg *in_seg;
int in_curs;
double x[2];
double y0, y1;
double a, b, c; /* line equation; ax+by+c = 0 for the line, a^2 + b^2 = 1,
and a>0 */
/* bottom point and intersection point stack */
int n_stack;
int n_stack_max;
ArtPoint *stack;
/* horiz commit list */
ArtActiveSeg *horiz_left, *horiz_right;
double horiz_x;
int horiz_delta_wind;
int seg_id;
};
typedef struct _ArtIntersectCtx ArtIntersectCtx;
struct _ArtIntersectCtx {
const ArtSVP *in;
ArtSvpWriter *out;
ArtPriQ *pq;
ArtActiveSeg *active_head;
double y;
ArtActiveSeg *horiz_first;
ArtActiveSeg *horiz_last;
/* segment index of next input segment to be added to pri q */
int in_curs;
};
#define EPSILON_A 1e-5 /* Threshold for breaking lines at point insertions */
/**
* art_svp_intersect_setup_seg: Set up an active segment from input segment.
* @seg: Active segment.
* @pri_pt: Priority queue point to initialize.
*
* Sets the x[], a, b, c, flags, and stack fields according to the
* line from the current cursor value. Sets the priority queue point
* to the bottom point of this line. Also advances the input segment
* cursor.
**/
static void art_svp_intersect_setup_seg(ArtActiveSeg *seg, ArtPriPoint *pri_pt) {
const ArtSVPSeg *in_seg = seg->in_seg;
int in_curs = seg->in_curs++;
double x0, y0, x1, y1;
double dx, dy, s;
double a, b, r2;
x0 = in_seg->points[in_curs].x;
y0 = in_seg->points[in_curs].y;
x1 = in_seg->points[in_curs + 1].x;
y1 = in_seg->points[in_curs + 1].y;
pri_pt->x = x1;
pri_pt->y = y1;
dx = x1 - x0;
dy = y1 - y0;
r2 = dx * dx + dy * dy;
s = r2 == 0 ? 1 : 1 / sqrt(r2);
seg->a = a = dy * s;
seg->b = b = -dx * s;
seg->c = -(a * x0 + b * y0);
seg->flags = (seg->flags & ~ART_ACTIVE_FLAGS_BNEG) | (dx > 0);
seg->x[0] = x0;
seg->x[1] = x1;
seg->y0 = y0;
seg->y1 = y1;
seg->n_stack = 1;
seg->stack[0].x = x1;
seg->stack[0].y = y1;
}
/**
* art_svp_intersect_add_horiz: Add point to horizontal list.
* @ctx: Intersector context.
* @seg: Segment with point to insert into horizontal list.
*
* Inserts @seg into horizontal list, keeping it in ascending horiz_x
* order.
*
* Note: the horiz_commit routine processes "clusters" of segs in the
* horiz list, all sharing the same horiz_x value. The cluster is
* processed in active list order, rather than horiz list order. Thus,
* the order of segs in the horiz list sharing the same horiz_x
* _should_ be irrelevant. Even so, we use b as a secondary sorting key,
* as a "belt and suspenders" defensive coding tactic.
**/
static void art_svp_intersect_add_horiz(ArtIntersectCtx *ctx, ArtActiveSeg *seg) {
ArtActiveSeg **pp = &ctx->horiz_last;
ArtActiveSeg *place;
ArtActiveSeg *place_right = NULL;
if (seg->flags & ART_ACTIVE_FLAGS_IN_HORIZ) {
warning("attempt to put segment in horiz list twice");
return;
}
seg->flags |= ART_ACTIVE_FLAGS_IN_HORIZ;
for (place = *pp; place != NULL && (place->horiz_x > seg->horiz_x ||
(place->horiz_x == seg->horiz_x &&
place->b < seg->b));
place = *pp) {
place_right = place;
pp = &place->horiz_left;
}
*pp = seg;
seg->horiz_left = place;
seg->horiz_right = place_right;
if (place == NULL)
ctx->horiz_first = seg;
else
place->horiz_right = seg;
}
static void art_svp_intersect_push_pt(ArtIntersectCtx *ctx, ArtActiveSeg *seg,
double x, double y) {
ArtPriPoint *pri_pt;
int n_stack = seg->n_stack;
if (n_stack == seg->n_stack_max)
art_expand(seg->stack, ArtPoint, seg->n_stack_max);
seg->stack[n_stack].x = x;
seg->stack[n_stack].y = y;
seg->n_stack++;
seg->x[1] = x;
seg->y1 = y;
pri_pt = art_new(ArtPriPoint, 1);
if (!pri_pt)
error("[art_svp_intersect_push_pt] Cannot allocate memory");
pri_pt->x = x;
pri_pt->y = y;
pri_pt->user_data = seg;
art_pri_insert(ctx->pq, pri_pt);
}
typedef enum {
ART_BREAK_LEFT = 1,
ART_BREAK_RIGHT = 2
} ArtBreakFlags;
/**
* art_svp_intersect_break: Break an active segment.
*
* Note: y must be greater than the top point's y, and less than
* the bottom's.
*
* Return value: x coordinate of break point.
*/
static double art_svp_intersect_break(ArtIntersectCtx *ctx, ArtActiveSeg *seg,
double x_ref, double y, ArtBreakFlags break_flags) {
double x0, y0, x1, y1;
const ArtSVPSeg *in_seg = seg->in_seg;
int in_curs = seg->in_curs;
double x;
x0 = in_seg->points[in_curs - 1].x;
y0 = in_seg->points[in_curs - 1].y;
x1 = in_seg->points[in_curs].x;
y1 = in_seg->points[in_curs].y;
x = x0 + (x1 - x0) * ((y - y0) / (y1 - y0));
if ((break_flags == ART_BREAK_LEFT && x > x_ref) ||
(break_flags == ART_BREAK_RIGHT && x < x_ref)) {
}
/* I think we can count on min(x0, x1) <= x <= max(x0, x1) with sane
arithmetic, but it might be worthwhile to check just in case. */
if (y > ctx->y)
art_svp_intersect_push_pt(ctx, seg, x, y);
else {
seg->x[0] = x;
seg->y0 = y;
seg->horiz_x = x;
art_svp_intersect_add_horiz(ctx, seg);
}
return x;
}
/**
* art_svp_intersect_add_point: Add a point, breaking nearby neighbors.
* @ctx: Intersector context.
* @x: X coordinate of point to add.
* @y: Y coordinate of point to add.
* @seg: "nearby" segment, or NULL if leftmost.
*
* Return value: Segment immediately to the left of the new point, or
* NULL if the new point is leftmost.
**/
static ArtActiveSeg *art_svp_intersect_add_point(ArtIntersectCtx *ctx, double x, double y,
ArtActiveSeg *seg, ArtBreakFlags break_flags) {
ArtActiveSeg *left, *right;
double x_min = x, x_max = x;
bool left_live, right_live;
double d;
double new_x;
ArtActiveSeg *test, *result = NULL;
double x_test;
left = seg;
if (left == NULL)
right = ctx->active_head;
else
right = left->right;
left_live = (break_flags & ART_BREAK_LEFT) && (left != NULL);
right_live = (break_flags & ART_BREAK_RIGHT) && (right != NULL);
while (left_live || right_live) {
if (left_live) {
if (x <= left->x[left->flags & ART_ACTIVE_FLAGS_BNEG] &&
/* It may be that one of these conjuncts turns out to be always
true. We test both anyway, to be defensive. */
y != left->y0 && y < left->y1) {
d = x_min * left->a + y * left->b + left->c;
if (d < EPSILON_A) {
new_x = art_svp_intersect_break(ctx, left, x_min, y,
ART_BREAK_LEFT);
if (new_x > x_max) {
x_max = new_x;
right_live = (right != NULL);
} else if (new_x < x_min)
x_min = new_x;
left = left->left;
left_live = (left != NULL);
} else
left_live = false;
} else
left_live = false;
} else if (right_live) {
if (x >= right->x[(right->flags & ART_ACTIVE_FLAGS_BNEG) ^ 1] &&
/* It may be that one of these conjuncts turns out to be always
true. We test both anyway, to be defensive. */
y != right->y0 && y < right->y1) {
d = x_max * right->a + y * right->b + right->c;
if (d > -EPSILON_A) {
new_x = art_svp_intersect_break(ctx, right, x_max, y,
ART_BREAK_RIGHT);
if (new_x < x_min) {
x_min = new_x;
left_live = (left != NULL);
} else if (new_x >= x_max)
x_max = new_x;
right = right->right;
right_live = (right != NULL);
} else
right_live = false;
} else
right_live = false;
}
}
/* Ascending order is guaranteed by break_flags. Thus, we don't need
to actually fix up non-ascending pairs. */
/* Now, (left, right) defines an interval of segments broken. Sort
into ascending x order. */
test = left == NULL ? ctx->active_head : left->right;
result = left;
if (test != NULL && test != right) {
if (y == test->y0)
x_test = test->x[0];
else /* assert y == test->y1, I think */
x_test = test->x[1];
for (;;) {
if (x_test <= x)
result = test;
test = test->right;
if (test == right)
break;
new_x = x_test;
if (new_x < x_test) {
warning("art_svp_intersect_add_point: non-ascending x");
}
x_test = new_x;
}
}
return result;
}
static void art_svp_intersect_swap_active(ArtIntersectCtx *ctx,
ArtActiveSeg *left_seg, ArtActiveSeg *right_seg) {
right_seg->left = left_seg->left;
if (right_seg->left != NULL)
right_seg->left->right = right_seg;
else
ctx->active_head = right_seg;
left_seg->right = right_seg->right;
if (left_seg->right != NULL)
left_seg->right->left = left_seg;
left_seg->left = right_seg;
right_seg->right = left_seg;
}
/**
* art_svp_intersect_test_cross: Test crossing of a pair of active segments.
* @ctx: Intersector context.
* @left_seg: Left segment of the pair.
* @right_seg: Right segment of the pair.
* @break_flags: Flags indicating whether to break neighbors.
*
* Tests crossing of @left_seg and @right_seg. If there is a crossing,
* inserts the intersection point into both segments.
*
* Return value: True if the intersection took place at the current
* scan line, indicating further iteration is needed.
**/
static bool art_svp_intersect_test_cross(ArtIntersectCtx *ctx,
ArtActiveSeg *left_seg, ArtActiveSeg *right_seg,
ArtBreakFlags break_flags) {
double left_x0, left_y0, left_x1;
double left_y1 = left_seg->y1;
double right_y1 = right_seg->y1;
double d;
const ArtSVPSeg *in_seg;
int in_curs;
double d0, d1, t;
double x, y; /* intersection point */
if (left_seg->y0 == right_seg->y0 && left_seg->x[0] == right_seg->x[0]) {
/* Top points of left and right segments coincide. This case
feels like a bit of duplication - we may want to merge it
with the cases below. However, this way, we're sure that this
logic makes only localized changes. */
if (left_y1 < right_y1) {
/* Test left (x1, y1) against right segment */
left_x1 = left_seg->x[1];
if (left_x1 <
right_seg->x[(right_seg->flags & ART_ACTIVE_FLAGS_BNEG) ^ 1] ||
left_y1 == right_seg->y0)
return false;
d = left_x1 * right_seg->a + left_y1 * right_seg->b + right_seg->c;
if (d < -EPSILON_A)
return false;
else if (d < EPSILON_A) {
/* I'm unsure about the break flags here. */
double right_x1 = art_svp_intersect_break(ctx, right_seg,
left_x1, left_y1,
ART_BREAK_RIGHT);
if (left_x1 <= right_x1)
return false;
}
} else if (left_y1 > right_y1) {
/* Test right (x1, y1) against left segment */
double right_x1 = right_seg->x[1];
if (right_x1 > left_seg->x[left_seg->flags & ART_ACTIVE_FLAGS_BNEG] ||
right_y1 == left_seg->y0)
return false;
d = right_x1 * left_seg->a + right_y1 * left_seg->b + left_seg->c;
if (d > EPSILON_A)
return false;
else if (d > -EPSILON_A) {
/* See above regarding break flags. */
left_x1 = art_svp_intersect_break(ctx, left_seg,
right_x1, right_y1,
ART_BREAK_LEFT);
if (left_x1 <= right_x1)
return false;
}
} else { /* left_y1 == right_y1 */
left_x1 = left_seg->x[1];
double right_x1 = right_seg->x[1];
if (left_x1 <= right_x1)
return false;
}
art_svp_intersect_swap_active(ctx, left_seg, right_seg);
return true;
}
if (left_y1 < right_y1) {
/* Test left (x1, y1) against right segment */
left_x1 = left_seg->x[1];
if (left_x1 <
right_seg->x[(right_seg->flags & ART_ACTIVE_FLAGS_BNEG) ^ 1] ||
left_y1 == right_seg->y0)
return false;
d = left_x1 * right_seg->a + left_y1 * right_seg->b + right_seg->c;
if (d < -EPSILON_A)
return false;
else if (d < EPSILON_A) {
double right_x1 = art_svp_intersect_break(ctx, right_seg,
left_x1, left_y1,
ART_BREAK_RIGHT);
if (left_x1 <= right_x1)
return false;
}
} else if (left_y1 > right_y1) {
/* Test right (x1, y1) against left segment */
double right_x1 = right_seg->x[1];
if (right_x1 > left_seg->x[left_seg->flags & ART_ACTIVE_FLAGS_BNEG] ||
right_y1 == left_seg->y0)
return false;
d = right_x1 * left_seg->a + right_y1 * left_seg->b + left_seg->c;
if (d > EPSILON_A)
return false;
else if (d > -EPSILON_A) {
left_x1 = art_svp_intersect_break(ctx, left_seg,
right_x1, right_y1,
ART_BREAK_LEFT);
if (left_x1 <= right_x1)
return false;
}
} else { /* left_y1 == right_y1 */
left_x1 = left_seg->x[1];
double right_x1 = right_seg->x[1];
if (left_x1 <= right_x1)
return false;
}
/* The segments cross. Find the intersection point. */
in_seg = left_seg->in_seg;
in_curs = left_seg->in_curs;
left_x0 = in_seg->points[in_curs - 1].x;
left_y0 = in_seg->points[in_curs - 1].y;
left_x1 = in_seg->points[in_curs].x;
left_y1 = in_seg->points[in_curs].y;
d0 = left_x0 * right_seg->a + left_y0 * right_seg->b + right_seg->c;
d1 = left_x1 * right_seg->a + left_y1 * right_seg->b + right_seg->c;
if (d0 == d1) {
x = left_x0;
y = left_y0;
} else {
/* Is this division always safe? It could possibly overflow. */
t = d0 / (d0 - d1);
if (t <= 0) {
x = left_x0;
y = left_y0;
} else if (t >= 1) {
x = left_x1;
y = left_y1;
} else {
x = left_x0 + t * (left_x1 - left_x0);
y = left_y0 + t * (left_y1 - left_y0);
}
}
/* Make sure intersection point is within bounds of right seg. */
if (y < right_seg->y0) {
x = right_seg->x[0];
y = right_seg->y0;
} else if (y > right_seg->y1) {
x = right_seg->x[1];
y = right_seg->y1;
} else if (x < right_seg->x[(right_seg->flags & ART_ACTIVE_FLAGS_BNEG) ^ 1])
x = right_seg->x[(right_seg->flags & ART_ACTIVE_FLAGS_BNEG) ^ 1];
else if (x > right_seg->x[right_seg->flags & ART_ACTIVE_FLAGS_BNEG])
x = right_seg->x[right_seg->flags & ART_ACTIVE_FLAGS_BNEG];
if (y == left_seg->y0) {
if (y != right_seg->y0) {
art_svp_intersect_push_pt(ctx, right_seg, x, y);
if ((break_flags & ART_BREAK_RIGHT) && right_seg->right != NULL)
art_svp_intersect_add_point(ctx, x, y, right_seg->right,
break_flags);
} else {
/* Intersection takes place at current scan line; process
immediately rather than queueing intersection point into
priq. */
ArtActiveSeg *winner, *loser;
/* Choose "most vertical" segement */
if (left_seg->a > right_seg->a) {
winner = left_seg;
loser = right_seg;
} else {
winner = right_seg;
loser = left_seg;
}
loser->x[0] = winner->x[0];
loser->horiz_x = loser->x[0];
loser->horiz_delta_wind += loser->delta_wind;
winner->horiz_delta_wind -= loser->delta_wind;
art_svp_intersect_swap_active(ctx, left_seg, right_seg);
return true;
}
} else if (y == right_seg->y0) {
art_svp_intersect_push_pt(ctx, left_seg, x, y);
if ((break_flags & ART_BREAK_LEFT) && left_seg->left != NULL)
art_svp_intersect_add_point(ctx, x, y, left_seg->left,
break_flags);
} else {
/* Insert the intersection point into both segments. */
art_svp_intersect_push_pt(ctx, left_seg, x, y);
art_svp_intersect_push_pt(ctx, right_seg, x, y);
if ((break_flags & ART_BREAK_LEFT) && left_seg->left != NULL)
art_svp_intersect_add_point(ctx, x, y, left_seg->left, break_flags);
if ((break_flags & ART_BREAK_RIGHT) && right_seg->right != NULL)
art_svp_intersect_add_point(ctx, x, y, right_seg->right, break_flags);
}
return false;
}
/**
* art_svp_intersect_active_delete: Delete segment from active list.
* @ctx: Intersection context.
* @seg: Segment to delete.
*
* Deletes @seg from the active list.
**/
static void art_svp_intersect_active_delete(ArtIntersectCtx *ctx, ArtActiveSeg *seg) {
ArtActiveSeg *left = seg->left, *right = seg->right;
if (left != NULL)
left->right = right;
else
ctx->active_head = right;
if (right != NULL)
right->left = left;
}
/**
* art_svp_intersect_active_free: Free an active segment.
* @seg: Segment to delete.
*
* Frees @seg.
**/
static void art_svp_intersect_active_free(ArtActiveSeg *seg) {
free(seg->stack);
free(seg);
}
/**
* art_svp_intersect_insert_cross: Test crossings of newly inserted line.
*
* Tests @seg against its left and right neighbors for intersections.
* Precondition: the line in @seg is not purely horizontal.
**/
static void art_svp_intersect_insert_cross(ArtIntersectCtx *ctx,
ArtActiveSeg *seg) {
ArtActiveSeg *left = seg, *right = seg;
for (;;) {
if (left != NULL) {
ArtActiveSeg *leftc;
for (leftc = left->left; leftc != NULL; leftc = leftc->left)
if (!(leftc->flags & ART_ACTIVE_FLAGS_DEL))
break;
if (leftc != NULL &&
art_svp_intersect_test_cross(ctx, leftc, left,
ART_BREAK_LEFT)) {
if (left == right || right == NULL)
right = left->right;
} else {
left = NULL;
}
} else if (right != NULL && right->right != NULL) {
ArtActiveSeg *rightc;
for (rightc = right->right; rightc != NULL; rightc = rightc->right)
if (!(rightc->flags & ART_ACTIVE_FLAGS_DEL))
break;
if (rightc != NULL &&
art_svp_intersect_test_cross(ctx, right, rightc,
ART_BREAK_RIGHT)) {
if (left == right || left == NULL)
left = right->left;
} else {
right = NULL;
}
} else
break;
}
}
/**
* art_svp_intersect_horiz: Add horizontal line segment.
* @ctx: Intersector context.
* @seg: Segment on which to add horizontal line.
* @x0: Old x position.
* @x1: New x position.
*
* Adds a horizontal line from @x0 to @x1, and updates the current
* location of @seg to @x1.
**/
static void art_svp_intersect_horiz(ArtIntersectCtx *ctx, ArtActiveSeg *seg,
double x0, double x1) {
ArtActiveSeg *hs;
if (x0 == x1)
return;
hs = art_new(ArtActiveSeg, 1);
if (!hs)
error("[art_svp_intersect_horiz] Cannot allocate memory");
hs->flags = ART_ACTIVE_FLAGS_DEL | (seg->flags & ART_ACTIVE_FLAGS_OUT);
if (seg->flags & ART_ACTIVE_FLAGS_OUT) {
ArtSvpWriter *swr = ctx->out;
swr->add_point(swr, seg->seg_id, x0, ctx->y);
}
hs->seg_id = seg->seg_id;
hs->horiz_x = x0;
hs->horiz_delta_wind = seg->delta_wind;
hs->stack = NULL;
/* Ideally, the (a, b, c) values will never be read. However, there
are probably some tests remaining that don't check for _DEL
before evaluating the line equation. For those, these
initializations will at least prevent a UMR of the values, which
can crash on some platforms. */
hs->a = 0.0;
hs->b = 0.0;
hs->c = 0.0;
seg->horiz_delta_wind -= seg->delta_wind;
art_svp_intersect_add_horiz(ctx, hs);
if (x0 > x1) {
ArtActiveSeg *left;
bool first = true;
for (left = seg->left; left != NULL; left = seg->left) {
int left_bneg = left->flags & ART_ACTIVE_FLAGS_BNEG;
if (left->x[left_bneg] <= x1)
break;
if (left->x[left_bneg ^ 1] <= x1 &&
x1 *left->a + ctx->y *left->b + left->c >= 0)
break;
if (left->y0 != ctx->y && left->y1 != ctx->y) {
art_svp_intersect_break(ctx, left, x1, ctx->y, ART_BREAK_LEFT);
}
art_svp_intersect_swap_active(ctx, left, seg);
if (first && left->right != NULL) {
art_svp_intersect_test_cross(ctx, left, left->right,
ART_BREAK_RIGHT);
first = false;
}
}
} else {
ArtActiveSeg *right;
bool first = true;
for (right = seg->right; right != NULL; right = seg->right) {
int right_bneg = right->flags & ART_ACTIVE_FLAGS_BNEG;
if (right->x[right_bneg ^ 1] >= x1)
break;
if (right->x[right_bneg] >= x1 &&
x1 *right->a + ctx->y *right->b + right->c <= 0)
break;
if (right->y0 != ctx->y && right->y1 != ctx->y) {
art_svp_intersect_break(ctx, right, x1, ctx->y,
ART_BREAK_LEFT);
}
art_svp_intersect_swap_active(ctx, seg, right);
if (first && right->left != NULL) {
art_svp_intersect_test_cross(ctx, right->left, right,
ART_BREAK_RIGHT);
first = false;
}
}
}
seg->x[0] = x1;
seg->x[1] = x1;
seg->horiz_x = x1;
seg->flags &= ~ART_ACTIVE_FLAGS_OUT;
}
/**
* art_svp_intersect_insert_line: Insert a line into the active list.
* @ctx: Intersector context.
* @seg: Segment containing line to insert.
*
* Inserts the line into the intersector context, taking care of any
* intersections, and adding the appropriate horizontal points to the
* active list.
**/
static void art_svp_intersect_insert_line(ArtIntersectCtx *ctx, ArtActiveSeg *seg) {
if (seg->y1 == seg->y0) {
art_svp_intersect_horiz(ctx, seg, seg->x[0], seg->x[1]);
} else {
art_svp_intersect_insert_cross(ctx, seg);
art_svp_intersect_add_horiz(ctx, seg);
}
}
static void art_svp_intersect_process_intersection(ArtIntersectCtx *ctx,
ArtActiveSeg *seg) {
int n_stack = --seg->n_stack;
seg->x[1] = seg->stack[n_stack - 1].x;
seg->y1 = seg->stack[n_stack - 1].y;
seg->x[0] = seg->stack[n_stack].x;
seg->y0 = seg->stack[n_stack].y;
seg->horiz_x = seg->x[0];
art_svp_intersect_insert_line(ctx, seg);
}
static void art_svp_intersect_advance_cursor(ArtIntersectCtx *ctx, ArtActiveSeg *seg,
ArtPriPoint *pri_pt) {
const ArtSVPSeg *in_seg = seg->in_seg;
int in_curs = seg->in_curs;
ArtSvpWriter *swr = seg->flags & ART_ACTIVE_FLAGS_OUT ? ctx->out : NULL;
if (swr != NULL)
swr->add_point(swr, seg->seg_id, seg->x[1], seg->y1);
if (in_curs + 1 == in_seg->n_points) {
ArtActiveSeg *left = seg->left, *right = seg->right;
seg->flags |= ART_ACTIVE_FLAGS_DEL;
art_svp_intersect_add_horiz(ctx, seg);
art_svp_intersect_active_delete(ctx, seg);
if (left != NULL && right != NULL)
art_svp_intersect_test_cross(ctx, left, right,
(ArtBreakFlags)(ART_BREAK_LEFT | ART_BREAK_RIGHT));
free(pri_pt);
} else {
seg->horiz_x = seg->x[1];
art_svp_intersect_setup_seg(seg, pri_pt);
art_pri_insert(ctx->pq, pri_pt);
art_svp_intersect_insert_line(ctx, seg);
}
}
static void art_svp_intersect_add_seg(ArtIntersectCtx *ctx, const ArtSVPSeg *in_seg) {
ArtActiveSeg *seg = art_new(ArtActiveSeg, 1);
ArtActiveSeg *test;
double x0, y0;
ArtActiveSeg *last = NULL;
ArtActiveSeg *left, *right;
ArtPriPoint *pri_pt = art_new(ArtPriPoint, 1);
if (!pri_pt)
error("[art_svp_intersect_add_seg] Cannot allocate memory");
seg->flags = 0;
seg->in_seg = in_seg;
seg->in_curs = 0;
seg->n_stack_max = 4;
seg->stack = art_new(ArtPoint, seg->n_stack_max);
seg->horiz_delta_wind = 0;
seg->wind_left = 0;
pri_pt->user_data = seg;
art_svp_intersect_setup_seg(seg, pri_pt);
art_pri_insert(ctx->pq, pri_pt);
/* Find insertion place for new segment */
/* This is currently a left-to-right scan, but should be replaced
with a binary search as soon as it's validated. */
x0 = in_seg->points[0].x;
y0 = in_seg->points[0].y;
for (test = ctx->active_head; test != NULL; test = test->right) {
double d;
int test_bneg = test->flags & ART_ACTIVE_FLAGS_BNEG;
if (x0 < test->x[test_bneg]) {
if (x0 < test->x[test_bneg ^ 1])
break;
d = x0 * test->a + y0 * test->b + test->c;
if (d < 0)
break;
}
last = test;
}
left = art_svp_intersect_add_point(ctx, x0, y0, last, (ArtBreakFlags)(ART_BREAK_LEFT | ART_BREAK_RIGHT));
seg->left = left;
if (left == NULL) {
right = ctx->active_head;
ctx->active_head = seg;
} else {
right = left->right;
left->right = seg;
}
seg->right = right;
if (right != NULL)
right->left = seg;
seg->delta_wind = in_seg->dir ? 1 : -1;
seg->horiz_x = x0;
art_svp_intersect_insert_line(ctx, seg);
}
/**
* art_svp_intersect_horiz_commit: Commit points in horiz list to output.
* @ctx: Intersection context.
*
* The main function of the horizontal commit is to output new
* points to the output writer.
*
* This "commit" pass is also where winding numbers are assigned,
* because doing it here provides much greater tolerance for inputs
* which are not in strict SVP order.
*
* Each cluster in the horiz_list contains both segments that are in
* the active list (ART_ACTIVE_FLAGS_DEL is false) and that are not,
* and are scheduled to be deleted (ART_ACTIVE_FLAGS_DEL is true). We
* need to deal with both.
**/
static void art_svp_intersect_horiz_commit(ArtIntersectCtx *ctx) {
ArtActiveSeg *seg;
int winding_number = 0; /* initialization just to avoid warning */
int horiz_wind = 0;
double last_x = 0; /* initialization just to avoid warning */
/* Output points to svp writer. */
for (seg = ctx->horiz_first; seg != NULL;) {
/* Find a cluster with common horiz_x, */
ArtActiveSeg *curs;
double x = seg->horiz_x;
/* Generate any horizontal segments. */
if (horiz_wind != 0) {
ArtSvpWriter *swr = ctx->out;
int seg_id;
seg_id = swr->add_segment(swr, winding_number, horiz_wind,
last_x, ctx->y);
swr->add_point(swr, seg_id, x, ctx->y);
swr->close_segment(swr, seg_id);
}
/* Find first active segment in cluster. */
for (curs = seg; curs != NULL && curs->horiz_x == x;
curs = curs->horiz_right)
if (!(curs->flags & ART_ACTIVE_FLAGS_DEL))
break;
if (curs != NULL && curs->horiz_x == x) {
/* There exists at least one active segment in this cluster. */
/* Find beginning of cluster. */
for (; curs->left != NULL; curs = curs->left)
if (curs->left->horiz_x != x)
break;
if (curs->left != NULL)
winding_number = curs->left->wind_left + curs->left->delta_wind;
else
winding_number = 0;
do {
if (!(curs->flags & ART_ACTIVE_FLAGS_OUT) ||
curs->wind_left != winding_number) {
ArtSvpWriter *swr = ctx->out;
if (curs->flags & ART_ACTIVE_FLAGS_OUT) {
swr->add_point(swr, curs->seg_id,
curs->horiz_x, ctx->y);
swr->close_segment(swr, curs->seg_id);
}
curs->seg_id = swr->add_segment(swr, winding_number,
curs->delta_wind,
x, ctx->y);
curs->flags |= ART_ACTIVE_FLAGS_OUT;
}
curs->wind_left = winding_number;
winding_number += curs->delta_wind;
curs = curs->right;
} while (curs != NULL && curs->horiz_x == x);
}
/* Skip past cluster. */
do {
ArtActiveSeg *next = seg->horiz_right;
seg->flags &= ~ART_ACTIVE_FLAGS_IN_HORIZ;
horiz_wind += seg->horiz_delta_wind;
seg->horiz_delta_wind = 0;
if (seg->flags & ART_ACTIVE_FLAGS_DEL) {
if (seg->flags & ART_ACTIVE_FLAGS_OUT) {
ArtSvpWriter *swr = ctx->out;
swr->close_segment(swr, seg->seg_id);
}
art_svp_intersect_active_free(seg);
}
seg = next;
} while (seg != NULL && seg->horiz_x == x);
last_x = x;
}
ctx->horiz_first = NULL;
ctx->horiz_last = NULL;
}
void art_svp_intersector(const ArtSVP *in, ArtSvpWriter *out) {
ArtIntersectCtx *ctx;
ArtPriQ *pq;
ArtPriPoint *first_point;
if (in->n_segs == 0)
return;
ctx = art_new(ArtIntersectCtx, 1);
if (!ctx)
error("[art_svp_intersector] Cannot allocate memory");
ctx->in = in;
ctx->out = out;
pq = art_pri_new();
ctx->pq = pq;
ctx->active_head = NULL;
ctx->horiz_first = NULL;
ctx->horiz_last = NULL;
ctx->in_curs = 0;
first_point = art_new(ArtPriPoint, 1);
if (!first_point)
error("[art_svp_intersector] Cannot allocate memory");
first_point->x = in->segs[0].points[0].x;
first_point->y = in->segs[0].points[0].y;
first_point->user_data = NULL;
ctx->y = first_point->y;
art_pri_insert(pq, first_point);
while (!art_pri_empty(pq)) {
ArtPriPoint *pri_point = art_pri_choose(pq);
ArtActiveSeg *seg = (ArtActiveSeg *)pri_point->user_data;
if (ctx->y != pri_point->y) {
art_svp_intersect_horiz_commit(ctx);
ctx->y = pri_point->y;
}
if (seg == NULL) {
/* Insert new segment from input */
const ArtSVPSeg *in_seg = &in->segs[ctx->in_curs++];
art_svp_intersect_add_seg(ctx, in_seg);
if (ctx->in_curs < in->n_segs) {
const ArtSVPSeg *next_seg = &in->segs[ctx->in_curs];
pri_point->x = next_seg->points[0].x;
pri_point->y = next_seg->points[0].y;
/* user_data is already NULL */
art_pri_insert(pq, pri_point);
} else
free(pri_point);
} else {
int n_stack = seg->n_stack;
if (n_stack > 1) {
art_svp_intersect_process_intersection(ctx, seg);
free(pri_point);
} else {
art_svp_intersect_advance_cursor(ctx, seg, pri_point);
}
}
}
art_svp_intersect_horiz_commit(ctx);
art_pri_free(pq);
free(ctx);
}
/* The spiffy antialiased renderer for sorted vector paths. */
typedef double artfloat;
struct ArtSVPRenderAAIter {
const ArtSVP *svp;
int x0, x1;
int y;
int seg_ix;
int *active_segs;
int n_active_segs;
int *cursor;
artfloat *seg_x;
artfloat *seg_dx;
ArtSVPRenderAAStep *steps;
};
static void art_svp_render_insert_active(int i, int *active_segs, int n_active_segs,
artfloat *seg_x, artfloat *seg_dx) {
int j;
artfloat x;
int tmp1, tmp2;
/* this is a cheap hack to get ^'s sorted correctly */
x = seg_x[i] + 0.001 * seg_dx[i];
for (j = 0; j < n_active_segs && seg_x[active_segs[j]] < x; j++)
;
tmp1 = i;
while (j < n_active_segs) {
tmp2 = active_segs[j];
active_segs[j] = tmp1;
tmp1 = tmp2;
j++;
}
active_segs[j] = tmp1;
}
static void art_svp_render_delete_active(int *active_segs, int j, int n_active_segs) {
int k;
for (k = j; k < n_active_segs; k++)
active_segs[k] = active_segs[k + 1];
}
/* Render the sorted vector path in the given rectangle, antialiased.
This interface uses a callback for the actual pixel rendering. The
callback is called y1 - y0 times (once for each scan line). The y
coordinate is given as an argument for convenience (it could be
stored in the callback's private data and incremented on each
call).
The rendered polygon is represented in a semi-runlength format: a
start value and a sequence of "steps". Each step has an x
coordinate and a value delta. The resulting value at position x is
equal to the sum of the start value and all step delta values for
which the step x coordinate is less than or equal to x. An
efficient algorithm will traverse the steps left to right, keeping
a running sum.
All x coordinates in the steps are guaranteed to be x0 <= x < x1.
(This guarantee is a change from the gfonted vpaar renderer, and is
designed to simplify the callback).
There is now a further guarantee that no two steps will have the
same x value. This may allow for further speedup and simplification
of renderers.
The value 0x8000 represents 0% coverage by the polygon, while
0xff8000 represents 100% coverage. This format is designed so that
>> 16 results in a standard 0x00..0xff value range, with nice
rounding.
Status of this routine:
Basic correctness: OK
Numerical stability: pretty good, although probably not
bulletproof.
Speed: Needs more aggressive culling of bounding boxes. Can
probably speed up the [x0,x1) clipping of step values. Can do more
of the step calculation in fixed point.
Precision: No known problems, although it should be tested
thoroughly, especially for symmetry.
*/
ArtSVPRenderAAIter *art_svp_render_aa_iter(const ArtSVP *svp,
int x0, int y0, int x1, int y1) {
ArtSVPRenderAAIter *iter = art_new(ArtSVPRenderAAIter, 1);
if (!iter)
error("[art_svp_render_aa_iter] Cannot allocate memory");
iter->svp = svp;
iter->y = y0;
iter->x0 = x0;
iter->x1 = x1;
iter->seg_ix = 0;
iter->active_segs = art_new(int, svp->n_segs);
iter->cursor = art_new(int, svp->n_segs);
iter->seg_x = art_new(artfloat, svp->n_segs);
iter->seg_dx = art_new(artfloat, svp->n_segs);
iter->steps = art_new(ArtSVPRenderAAStep, x1 - x0);
iter->n_active_segs = 0;
return iter;
}
#define ADD_STEP(xpos, xdelta) \
/* stereotype code fragment for adding a step */ \
if (n_steps == 0 || steps[n_steps - 1].x < xpos) { \
sx = n_steps; \
steps[sx].x = xpos; \
steps[sx].delta = xdelta; \
n_steps++; \
} else { \
for (sx = n_steps; sx > 0; sx--) { \
if (steps[sx - 1].x == xpos) { \
steps[sx - 1].delta += xdelta; \
sx = n_steps; \
break; \
} else if (steps[sx - 1].x < xpos) { \
break; \
} \
} \
if (sx < n_steps) { \
memmove (&steps[sx + 1], &steps[sx], \
(n_steps - sx) * sizeof(steps[0])); \
steps[sx].x = xpos; \
steps[sx].delta = xdelta; \
n_steps++; \
} \
}
void art_svp_render_aa_iter_step(ArtSVPRenderAAIter *iter, int *p_start,
ArtSVPRenderAAStep **p_steps, int *p_n_steps) {
const ArtSVP *svp = iter->svp;
int *active_segs = iter->active_segs;
int n_active_segs = iter->n_active_segs;
int *cursor = iter->cursor;
artfloat *seg_x = iter->seg_x;
artfloat *seg_dx = iter->seg_dx;
int i = iter->seg_ix;
int j;
int x0 = iter->x0;
int x1 = iter->x1;
int y = iter->y;
int seg_index;
int x;
ArtSVPRenderAAStep *steps = iter->steps;
int n_steps;
artfloat y_top, y_bot;
artfloat x_top, x_bot;
artfloat x_min, x_max;
int ix_min, ix_max;
artfloat delta; /* delta should be int too? */
int last, this_;
int xdelta;
artfloat rslope, drslope;
int start;
const ArtSVPSeg *seg;
int curs;
artfloat dy;
int sx;
/* insert new active segments */
for (; i < svp->n_segs && svp->segs[i].bbox.y0 < y + 1; i++) {
if (svp->segs[i].bbox.y1 > y &&
svp->segs[i].bbox.x0 < x1) {
seg = &svp->segs[i];
/* move cursor to topmost vector which overlaps [y,y+1) */
for (curs = 0; seg->points[curs + 1].y < y; curs++)
;
cursor[i] = curs;
dy = seg->points[curs + 1].y - seg->points[curs].y;
if (fabs(dy) >= EPSILON_6)
seg_dx[i] = (seg->points[curs + 1].x - seg->points[curs].x) /
dy;
else
seg_dx[i] = 1e12;
seg_x[i] = seg->points[curs].x +
(y - seg->points[curs].y) * seg_dx[i];
art_svp_render_insert_active(i, active_segs, n_active_segs++,
seg_x, seg_dx);
}
}
n_steps = 0;
/* render the runlengths, advancing and deleting as we go */
start = 0x8000;
for (j = 0; j < n_active_segs; j++) {
seg_index = active_segs[j];
seg = &svp->segs[seg_index];
curs = cursor[seg_index];
while (curs != seg->n_points - 1 &&
seg->points[curs].y < y + 1) {
y_top = y;
if (y_top < seg->points[curs].y)
y_top = seg->points[curs].y;
y_bot = y + 1;
if (y_bot > seg->points[curs + 1].y)
y_bot = seg->points[curs + 1].y;
if (y_top != y_bot) {
delta = (seg->dir ? 16711680.0 : -16711680.0) *
(y_bot - y_top);
x_top = seg_x[seg_index] + (y_top - y) * seg_dx[seg_index];
x_bot = seg_x[seg_index] + (y_bot - y) * seg_dx[seg_index];
if (x_top < x_bot) {
x_min = x_top;
x_max = x_bot;
} else {
x_min = x_bot;
x_max = x_top;
}
ix_min = (int)floor(x_min);
ix_max = (int)floor(x_max);
if (ix_min >= x1) {
/* skip; it starts to the right of the render region */
} else if (ix_max < x0)
/* it ends to the left of the render region */
start += (int)delta;
else if (ix_min == ix_max) {
/* case 1, antialias a single pixel */
xdelta = (int)((ix_min + 1 - (x_min + x_max) * 0.5) * delta);
ADD_STEP(ix_min, xdelta)
if (ix_min + 1 < x1) {
xdelta = (int)(delta - xdelta);
ADD_STEP(ix_min + 1, xdelta)
}
} else {
/* case 2, antialias a run */
rslope = 1.0 / fabs(seg_dx[seg_index]);
drslope = delta * rslope;
last =
(int)(drslope * 0.5 *
(ix_min + 1 - x_min) * (ix_min + 1 - x_min));
xdelta = last;
if (ix_min >= x0) {
ADD_STEP(ix_min, xdelta)
x = ix_min + 1;
} else {
start += last;
x = x0;
}
if (ix_max > x1)
ix_max = x1;
for (; x < ix_max; x++) {
this_ = (int)((seg->dir ? 16711680.0 : -16711680.0) * rslope *
(x + 0.5 - x_min));
xdelta = this_ - last;
last = this_;
ADD_STEP(x, xdelta)
}
if (x < x1) {
this_ =
(int)(delta * (1 - 0.5 *
(x_max - ix_max) * (x_max - ix_max) *
rslope));
xdelta = this_ - last;
last = this_;
ADD_STEP(x, xdelta)
if (x + 1 < x1) {
xdelta = (int)(delta - last);
ADD_STEP(x + 1, xdelta)
}
}
}
}
curs++;
if (curs != seg->n_points - 1 &&
seg->points[curs].y < y + 1) {
dy = seg->points[curs + 1].y - seg->points[curs].y;
if (fabs(dy) >= EPSILON_6)
seg_dx[seg_index] = (seg->points[curs + 1].x -
seg->points[curs].x) / dy;
else
seg_dx[seg_index] = 1e12;
seg_x[seg_index] = seg->points[curs].x +
(y - seg->points[curs].y) * seg_dx[seg_index];
}
/* break here, instead of duplicating predicate in while? */
}
if (seg->points[curs].y >= y + 1) {
curs--;
cursor[seg_index] = curs;
seg_x[seg_index] += seg_dx[seg_index];
} else {
art_svp_render_delete_active(active_segs, j--,
--n_active_segs);
}
}
*p_start = start;
*p_steps = steps;
*p_n_steps = n_steps;
iter->seg_ix = i;
iter->n_active_segs = n_active_segs;
iter->y++;
}
void art_svp_render_aa_iter_done(ArtSVPRenderAAIter *iter) {
free(iter->steps);
free(iter->seg_dx);
free(iter->seg_x);
free(iter->cursor);
free(iter->active_segs);
free(iter);
}
/**
* art_svp_render_aa: Render SVP antialiased.
* @svp: The #ArtSVP to render.
* @x0: Left coordinate of destination rectangle.
* @y0: Top coordinate of destination rectangle.
* @x1: Right coordinate of destination rectangle.
* @y1: Bottom coordinate of destination rectangle.
* @callback: The callback which actually paints the pixels.
* @callback_data: Private data for @callback.
*
* Renders the sorted vector path in the given rectangle, antialiased.
*
* This interface uses a callback for the actual pixel rendering. The
* callback is called @y1 - @y0 times (once for each scan line). The y
* coordinate is given as an argument for convenience (it could be
* stored in the callback's private data and incremented on each
* call).
*
* The rendered polygon is represented in a semi-runlength format: a
* start value and a sequence of "steps". Each step has an x
* coordinate and a value delta. The resulting value at position x is
* equal to the sum of the start value and all step delta values for
* which the step x coordinate is less than or equal to x. An
* efficient algorithm will traverse the steps left to right, keeping
* a running sum.
*
* All x coordinates in the steps are guaranteed to be @x0 <= x < @x1.
* (This guarantee is a change from the gfonted vpaar renderer from
* which this routine is derived, and is designed to simplify the
* callback).
*
* The value 0x8000 represents 0% coverage by the polygon, while
* 0xff8000 represents 100% coverage. This format is designed so that
* >> 16 results in a standard 0x00..0xff value range, with nice
* rounding.
*
**/
void art_svp_render_aa(const ArtSVP *svp,
int x0, int y0, int x1, int y1,
void (*callback)(void *callback_data,
int y,
int start,
ArtSVPRenderAAStep *steps, int n_steps),
void *callback_data) {
ArtSVPRenderAAIter *iter;
int y;
int start;
ArtSVPRenderAAStep *steps;
int n_steps;
iter = art_svp_render_aa_iter(svp, x0, y0, x1, y1);
for (y = y0; y < y1; y++) {
art_svp_render_aa_iter_step(iter, &start, &steps, &n_steps);
(*callback)(callback_data, y, start, steps, n_steps);
}
art_svp_render_aa_iter_done(iter);
}
} // End of namespace Sword25
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