gerbolyze/svg-flatten/src/svg_color.cpp

/*
 * 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 "svg_color.h"

#include <assert.h>
#include <string>
#include <cmath>

using namespace gerbolyze;
using namespace std;

/* Map an SVG fill or stroke definition (color, but may also be a pattern) to a gerber color.
 *
 * This function handles transparency: Transparent SVG colors are mapped such that no gerber output is generated for
 * them.
 */
enum gerber_color gerbolyze::svg_color_to_gerber(string color, string opacity, enum gerber_color default_val, const RenderSettings &rset) {
    //cerr << "resolving svg color spec color=\"" << color << "\", opacity=\"" << opacity << "\", default=" << default_val << endl;
    float alpha = 1.0;
    if (!opacity.empty() && opacity[0] != '\0') {
        char *endptr = nullptr;
        alpha = strtof(opacity.data(), &endptr);
        assert(endptr);
        assert(*endptr == '\0');
    }

    if (color.empty()) {
        //cerr << "  -> default" << endl;
        return default_val;
    }

    if (color == "none") {
        //cerr << "  -> none" << endl;
        return GRB_NONE;
    }

    if (color.rfind("url(#", 0) != string::npos) {
        //cerr << "  -> pattern" << endl;
        return GRB_PATTERN_FILL;
    }

    if ((color.length() == 7 && color[0] == '#') || color.rfind("rgba", 0) != string::npos) {
        RGBAColor rgba(color);
        HSVColor hsv(rgba);

        if (alpha == 1.0)
            alpha = rgba.a;

        if (alpha < 0.5f) {
            //cerr << "  -> none" << endl;
            if (alpha > 0.01) {
                cerr << "Info: Found an object with opacity set to " << alpha << ". This object will be omitted from the output." << endl; 
            }

            return GRB_NONE;
        }

        if ((hsv.v >= 0.5) != rset.flip_color_interpretation) {
            //cerr << "  -> clear" << endl;
            return GRB_CLEAR;
        } else {
            //cerr << "  -> dark" << endl;
            return GRB_DARK;
        }

        if (hsv.v >= 0.4 && hsv.v <= 0.6) {
            cerr << "Warning: color \"" << color << "\" is ambiguous. Gerbolyze decides whether to map colors to clear or dark polarity by checking if their HSV value (i.e. brightness) is above 50 %. This color has a value of " << hsv.v << ", close to 50 %." << endl; 
        }
    }

    //cerr << "  -> dark" << endl;
    return GRB_DARK;
}

gerbolyze::RGBAColor::RGBAColor(string spec) {
    /* resvg/usvg v0.18.0 added support for rgba(...) color specs */
    if (spec.rfind("rgba(", 0) != string::npos) {
        /* "rgba(127, 127, 200, 255)" */
        std::regex reg("rgba\\(([0-9]+),([0-9]+),([0-9]+),([0-9]+)\\)");
        std::smatch match;

        assert(std::regex_match(spec, match, reg));

        int c[4];
        for (size_t i=0; i<4; i++) {
            assert (match.size() == 5);
            char *endptr = nullptr;
            string span = match[i+1].str();
            c[i] = strtoul(span.data(), &endptr, 10);
            assert(endptr && endptr != span.data());
            assert(*endptr == '\0');
        }

        assert (0 <= c[0] && c[0] <= 255);
        assert (0 <= c[1] && c[1] <= 255);
        assert (0 <= c[2] && c[2] <= 255);
        assert (0 <= c[3] && c[3] <= 255);

        r = c[0]/255.0f;
        g = c[1]/255.0f;
        b = c[2]/255.0f;
        a = c[3]/255.0f;

    } else {
        /* "#FF00E3" */
        assert(spec[0] == '#');
        char *endptr = nullptr;
        const char *c = spec.data();
        int rgb = strtol(c + 1, &endptr, 16);
        assert(endptr);
        assert(endptr == c + 7);
        assert(*endptr == '\0');
        r = ((rgb >> 16) & 0xff) / 255.0f;
        g = ((rgb >>  8) & 0xff) / 255.0f;
        b = ((rgb >>  0) & 0xff) / 255.0f;
        a = 1.0;
    }
};

gerbolyze::HSVColor::HSVColor(const RGBAColor &color) {
    float xmax = fmax(color.r, fmax(color.g, color.b));
    float xmin = fmin(color.r, fmin(color.g, color.b));
    float c = xmax - xmin;

    v = xmax;

    if (c == 0)
        h = 0;
    else if (v == color.r)
        h = 1/3 * (0 + (color.g - color.b) / c);
    else if (v == color.g)
        h = 1/3 * (2 + (color.b - color.r) / c);
    else //  v == color.b
        h = 1/3 * (4 + (color.r - color.g) / c);

    s = (v == 0) ? 0 : (c/v);
}

/* Invert gerber color */
enum gerber_color gerbolyze::gerber_color_invert(enum gerber_color color) {
    switch (color) {
        case GRB_CLEAR: return GRB_DARK;
        case GRB_DARK: return GRB_CLEAR;
        default: return color; /* none, pattern */
    }
}

/* Read node's fill attribute and convert it to a gerber color */
enum gerber_color gerbolyze::gerber_fill_color(const pugi::xml_node &node, const RenderSettings &rset) {
    return svg_color_to_gerber(node.attribute("fill").value(), node.attribute("fill-opacity").value(), GRB_DARK, rset);
}

/* Read node's stroke attribute and convert it to a gerber color */
enum gerber_color gerbolyze::gerber_stroke_color(const pugi::xml_node &node, const RenderSettings &rset) {
    return svg_color_to_gerber(node.attribute("stroke").value(), node.attribute("stroke-opacity").value(), GRB_NONE, rset);
}