1 files changed, 152 insertions, 0 deletions
diff --git a/share/extensions/spirograph.py b/share/extensions/spirograph.py
new file mode 100755
index 0000000..69e6995
--- /dev/null
+++ b/share/extensions/spirograph.py
@@ -0,0 +1,152 @@
+#! /usr/bin/env python
+# 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()