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-rw-r--r--svg-flatten/src/svg_path.cpp213
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+/*
+ * This file is part of gerbolyze, a vector image preprocessing toolchain
+ * Copyright (C) 2021 Jan Sebastian Götte <gerbolyze@jaseg.de>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <cmath>
+#include <assert.h>
+#include <iostream>
+#include <sstream>
+#include "cairo_clipper.hpp"
+#include "svg_import_defs.h"
+#include "svg_path.h"
+
+using namespace std;
+
+static void clipper_add_cairo_path(cairo_t *cr, ClipperLib::Clipper &c, bool closed) {
+ ClipperLib::Paths in_poly;
+ ClipperLib::cairo::cairo_to_clipper(cr, in_poly, CAIRO_PRECISION, ClipperLib::cairo::tNone);
+ c.AddPaths(in_poly, ClipperLib::ptSubject, closed);
+}
+
+static void path_to_clipper_via_cairo(cairo_t *cr, ClipperLib::Clipper &c, const pugi::char_t *path_data) {
+ istringstream d(path_data);
+
+ string cmd;
+ double x, y, c1x, c1y, c2x, c2y;
+
+ bool first = true;
+ bool path_is_empty = true;
+ while (!d.eof()) {
+ d >> cmd;
+ assert (!d.fail());
+ assert(!first || cmd == "M");
+
+ if (cmd == "Z") { /* Close path */
+ cairo_close_path(cr);
+ clipper_add_cairo_path(cr, c, /* closed= */ true);
+ cairo_new_path(cr);
+ path_is_empty = true;
+
+ } else if (cmd == "M") { /* Move to */
+ d >> x >> y;
+ /* We need to transform all points ourselves here, and cannot use the transform feature of cairo_to_clipper:
+ * Our transform may contain offsets, and clipper only passes its data into cairo's transform functions
+ * after scaling up to its internal fixed-point ints, but it does not scale the transform accordingly. This
+ * means a scale/rotation we set before calling clipper works out fine, but translations get lost as they
+ * get scaled by something like 1e-6.
+ */
+ cairo_user_to_device(cr, &x, &y);
+ assert (!d.fail());
+ if (!first)
+ clipper_add_cairo_path(cr, c, /* closed= */ false);
+ cairo_new_path (cr);
+ path_is_empty = true;
+ cairo_move_to(cr, x, y);
+
+ } else if (cmd == "L") { /* Line to */
+ d >> x >> y;
+ cairo_user_to_device(cr, &x, &y);
+ assert (!d.fail());
+ cairo_line_to(cr, x, y);
+ path_is_empty = false;
+
+ } else { /* Curve to */
+ assert(cmd == "C");
+ d >> c1x >> c1y; /* first control point */
+ cairo_user_to_device(cr, &c1x, &c1y);
+ d >> c2x >> c2y; /* second control point */
+ cairo_user_to_device(cr, &c2x, &c2y);
+ d >> x >> y; /* end point */
+ cairo_user_to_device(cr, &x, &y);
+ assert (!d.fail());
+ cairo_curve_to(cr, c1x, c1y, c2x, c2y, x, y);
+ path_is_empty = false;
+ }
+
+ first = false;
+ }
+ if (!path_is_empty) {
+ cairo_close_path(cr);
+ clipper_add_cairo_path(cr, c, /* closed= */ false);
+ }
+}
+
+void gerbolyze::load_svg_path(cairo_t *cr, const pugi::xml_node &node, ClipperLib::PolyTree &ptree) {
+ auto *path_data = node.attribute("d").value();
+ auto fill_rule = clipper_fill_rule(node);
+
+ /* For open paths, clipper does not correctly remove self-intersections. Thus, we pass everything into
+ * clipper twice: Once with all paths set to "closed" to compute fill areas, and once with correct
+ * open/closed properties for stroke offsetting. */
+ cairo_set_tolerance (cr, 0.1); /* FIXME make configurable, scale properly for units */
+ cairo_set_fill_rule(cr, CAIRO_FILL_RULE_WINDING);
+
+ ClipperLib::Clipper c;
+ c.StrictlySimple(true);
+ path_to_clipper_via_cairo(cr, c, path_data);
+ /* We canont clip the polygon here since that would produce incorrect results for our stroke. */
+ c.Execute(ClipperLib::ctUnion, ptree, fill_rule, ClipperLib::pftNonZero);
+}
+
+void gerbolyze::parse_dasharray(const pugi::xml_node &node, vector<double> &out) {
+ out.clear();
+
+ string val(node.attribute("stroke-dasharray").value());
+ if (val.empty() || val == "none")
+ return;
+
+ istringstream desc_stream(val);
+ while (!desc_stream.eof()) {
+ /* usvg says the array only contains unitless (px) values. I don't know what resvg does with percentages inside
+ * dash arrays. We just assume everything is a unitless number here. In case usvg passes through percentages,
+ * well, bad luck. They are a kind of weird thing inside a dash array in the first place. */
+ double d;
+ desc_stream >> d;
+ out.push_back(d);
+ }
+
+ assert(out.size() % 2 == 0); /* according to resvg spec */
+}
+
+/* Take a Clipper path in clipper-scaled document units, and apply the given SVG dash array to it. Do this by walking
+ * the path from start to end while emitting dashes. */
+void gerbolyze::dash_path(const ClipperLib::Path &in, ClipperLib::Paths &out, const vector<double> dasharray, double dash_offset) {
+ out.clear();
+ if (dasharray.empty() || in.size() < 2) {
+ out.push_back(in);
+ return;
+ }
+
+ size_t dash_idx = 0;
+ size_t num_dashes = dasharray.size();
+ while (dash_offset > dasharray[dash_idx]) {
+ dash_offset -= dasharray[dash_idx];
+ dash_idx = (dash_idx + 1) % num_dashes;
+ }
+
+ double dash_remaining = dasharray[dash_idx] - dash_offset;
+
+ ClipperLib::Path current_dash;
+ current_dash.push_back(in[0]);
+ double dbg_total_len = 0.0;
+ for (size_t i=1; i<in.size(); i++) {
+ ClipperLib::IntPoint p1(in[i-1]), p2(in[i]);
+
+ double x1 = p1.X / clipper_scale, y1 = p1.Y / clipper_scale, x2 = p2.X / clipper_scale, y2 = p2.Y / clipper_scale;
+ double dist = sqrt(pow(x2-x1, 2) + pow(y2-y1, 2));
+ dbg_total_len += dist;
+
+ if (dist < dash_remaining) {
+ /* dash extends beyond this segment, append this segment and continue. */
+ dash_remaining -= dist;
+ current_dash.push_back(p2);
+
+ } else {
+ /* dash started in some previous segment ends in this segment */
+ double dash_frac = dash_remaining/dist;
+ double x = x1 + (x2 - x1) * dash_frac,
+ y = y1 + (y2 - y1) * dash_frac;
+ ClipperLib::IntPoint intermediate {(ClipperLib::cInt)round(x * clipper_scale), (ClipperLib::cInt)round(y * clipper_scale)};
+
+ /* end this dash */
+ current_dash.push_back(intermediate);
+ if (dash_idx%2 == 0) { /* dash */
+ out.push_back(current_dash);
+ } /* else space */
+ dash_idx = (dash_idx + 1) % num_dashes;
+ double offset = dash_remaining;
+
+ /* start next dash */
+ current_dash.clear();
+ current_dash.push_back(intermediate);
+
+ /* handle case where multiple dashes fit into this segment */
+ while ((dist - offset) > dasharray[dash_idx]) {
+ offset += dasharray[dash_idx];
+
+ double dash_frac = offset/dist;
+ double x = x1 + (x2 - x1) * dash_frac,
+ y = y1 + (y2 - y1) * dash_frac;
+ ClipperLib::IntPoint intermediate {(ClipperLib::cInt)round(x * clipper_scale), (ClipperLib::cInt)round(y * clipper_scale)};
+
+ /* end this dash */
+ current_dash.push_back(intermediate);
+ if (dash_idx%2 == 0) { /* dash */
+ out.push_back(current_dash);
+ } /* else space */
+ dash_idx = (dash_idx + 1) % num_dashes;
+
+ /* start next dash */
+ current_dash.clear();
+ current_dash.push_back(intermediate);
+ }
+
+ dash_remaining = dasharray[dash_idx] - (dist - offset);
+ current_dash.push_back(p2);
+ }
+ }
+}
+