PrusaSlicer/src/libslic3r/NSVGUtils.cpp

#include "NSVGUtils.hpp"
#include "ClipperUtils.hpp"

using namespace Slic3r;

void NSVGUtils::flatten_cubic_bez(Polygon &polygon,
                                  float    tessTol,
                                  Vec2f    p1,
                                  Vec2f    p2,
                                  Vec2f    p3,
                                  Vec2f    p4,
                                  int      level)
{
    Vec2f p12  = (p1 + p2) * 0.5f;
    Vec2f p23  = (p2 + p3) * 0.5f;
    Vec2f p34  = (p3 + p4) * 0.5f;
    Vec2f p123 = (p12 + p23) * 0.5f;

    Vec2f pd  = p4 - p1;
    Vec2f pd2 = p2 - p4;
    float d2  = std::abs(pd2.x() * pd.y() - pd2.y() * pd.x());
    Vec2f pd3 = p3 - p4;
    float d3  = std::abs(pd3.x() * pd.y() - pd3.y() * pd.x());
    float d23 = d2 + d3;

    if ((d23 * d23) < tessTol * (pd.x() * pd.x() + pd.y() * pd.y())) {
        polygon.points.emplace_back(p4.x(), p4.y());
        return;
    }

    --level;
    if (level == 0) return;
    Vec2f p234  = (p23 + p34) * 0.5f;
    Vec2f p1234 = (p123 + p234) * 0.5f;
    flatten_cubic_bez(polygon, tessTol, p1, p12, p123, p1234, level);
    flatten_cubic_bez(polygon, tessTol, p1234, p234, p34, p4, level);
}

ExPolygons NSVGUtils::to_ExPolygons(NSVGimage *image,
                                    float      tessTol,
                                    int        max_level)
{
    Polygons polygons;
    for (NSVGshape *shape = image->shapes; shape != NULL;
         shape            = shape->next) {
        if (!(shape->flags & NSVG_FLAGS_VISIBLE)) continue;
        Slic3r::Polygon polygon;
        if (shape->fill.type != NSVG_PAINT_NONE) {
            for (NSVGpath *path = shape->paths; path != NULL;
                 path           = path->next) {
                // Flatten path
                polygon.points.emplace_back(path->pts[0], path->pts[1]);
                size_t path_size = (path->npts > 1) ?
                    static_cast<size_t>(path->npts - 1) : 0;
                for (size_t i = 0; i < path_size; i += 3) {
                    float *p = &path->pts[i * 2];
                    Vec2f  p1(p[0], p[1]), p2(p[2], p[3]), p3(p[4], p[5]),
                        p4(p[6], p[7]);
                    flatten_cubic_bez(polygon, tessTol, p1, p2, p3, p4,
                                      max_level);
                }
                if (path->closed) {
                    polygons.push_back(polygon);
                    polygon = Slic3r::Polygon();
                }
            }
        }
        polygons.push_back(polygon);
    }

    // Fix Y axis
    for (Polygon &polygon : polygons)
        for (Point &p : polygon.points) p.y() *= -1;

    return Slic3r::union_ex(polygons);
}