Reorg: move svg-flatten files into subdir

1 files changed, 213 insertions, 0 deletions

diff --git a/svg-flatten/src/svg_path.cpp b/svg-flatten/src/svg_path.cpp
new file mode 100644
index 0000000..537b5dd
--- /dev/null
+++ b/svg-flatten/src/svg_path.cpp
@@ -0,0 +1,213 @@
+/*
+ * 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);
+        }
+    }
+}
+