inkscape/share/extensions/spirograph.py

#! /usr/bin/env python3
# coding=utf-8
#
# Copyright (C) 2007 Joel Holdsworth joel@airwebreathe.org.uk
#
# 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 2 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, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
#

import math
import inkex


class Spirograph(inkex.EffectExtension):
    def add_arguments(self, pars):
        pars.add_argument(
            "--primaryr", type=float, default=100.0, help="The radius of the outer gear"
        )
        pars.add_argument(
            "--secondaryr",
            type=float,
            default=60.0,
            help="The radius of the inner gear",
        )
        pars.add_argument(
            "--penr",
            type=float,
            default=50.0,
            help="The distance of the pen from the inner gear",
        )
        pars.add_argument(
            "--gearplacement",
            default="inside",
            help="Selects whether the gear is inside or outside the ring",
        )
        pars.add_argument(
            "--rotation",
            type=float,
            default=0.0,
            help="The number of degrees to rotate the image by",
        )
        pars.add_argument(
            "--quality",
            type=int,
            default=16,
            help="The quality of the calculated output",
        )

    def effect(self):
        self.options.primaryr = self.svg.unittouu(str(self.options.primaryr) + "px")
        self.options.secondaryr = self.svg.unittouu(str(self.options.secondaryr) + "px")
        self.options.penr = self.svg.unittouu(str(self.options.penr) + "px")

        if self.options.secondaryr == 0:
            return
        if self.options.quality == 0:
            return

        if self.options.gearplacement.strip(" ").lower().startswith("outside"):
            a = self.options.primaryr + self.options.secondaryr
            flip = -1
        else:
            a = self.options.primaryr - self.options.secondaryr
            flip = 1

        ratio = a / self.options.secondaryr
        if ratio == 0:
            return
        scale = 2 * math.pi / (ratio * self.options.quality)

        rotation = -math.pi * self.options.rotation / 180

        new = inkex.PathElement()
        new.style = inkex.Style(stroke="#000000", fill="none", stroke_width="1.0")

        path_string = ""
        maxPointCount = 1000

        for i in range(maxPointCount):
            theta = i * scale

            view_center = self.svg.namedview.center
            x = (
                a * math.cos(theta + rotation)
                + self.options.penr * math.cos(ratio * theta + rotation) * flip
                + view_center[0]
            )
            y = (
                a * math.sin(theta + rotation)
                - self.options.penr * math.sin(ratio * theta + rotation)
                + view_center[1]
            )

            dx = (
                (
                    -a * math.sin(theta + rotation)
                    - ratio
                    * self.options.penr
                    * math.sin(ratio * theta + rotation)
                    * flip
                )
                * scale
                / 3
            )
            dy = (
                (
                    a * math.cos(theta + rotation)
                    - ratio * self.options.penr * math.cos(ratio * theta + rotation)
                )
                * scale
                / 3
            )

            if i <= 0:
                path_string += "M {},{} C {},{} ".format(
                    str(x), str(y), str(x + dx), str(y + dy)
                )
            else:
                path_string += "{},{} {},{}".format(
                    str(x - dx), str(y - dy), str(x), str(y)
                )

                if (
                    math.fmod(i / ratio, self.options.quality) == 0
                    and i % self.options.quality == 0
                ):
                    path_string += "Z"
                    break
                else:
                    if i == maxPointCount - 1:
                        pass  # we reached the allowed maximum of points, stop here
                    else:
                        path_string += " C {},{} ".format(str(x + dx), str(y + dy))

        new.path = path_string
        self.svg.get_current_layer().append(new)


if __name__ == "__main__":
    Spirograph().run()