1 files changed, 142 insertions, 0 deletions
diff --git a/share/extensions/interp.py b/share/extensions/interp.py
new file mode 100755
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+++ b/share/extensions/interp.py
@@ -0,0 +1,142 @@
+#!/usr/bin/env python
+# coding=utf-8
+#
+# Copyright (C) 2005 Aaron Spike, aaron@ekips.org
+#               2020 Jonathan Neuhauser, jonathan.neuhauser@outlook.com
+#
+# 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.
+#
+""" Interpolate between two paths, respecting their style """
+import copy
+
+import inkex
+from inkex.utils import pairwise
+from inkex.tween import (
+    AttributeInterpolator,
+    StyleInterpolator,
+    EqualSubsegmentsInterpolator,
+    FirstNodesInterpolator,
+)
+
+from inkex.localization import inkex_gettext as _
+
+
+class Interp(inkex.EffectExtension):
+    """Interpolate extension"""
+
+    def add_arguments(self, pars):
+        pars.add_argument(
+            "-e",
+            "--exponent",
+            type=float,
+            default=1.0,
+            help="values other than zero give non linear interpolation",
+        )
+        pars.add_argument(
+            "-s", "--steps", type=int, default=5, help="number of interpolation steps"
+        )
+        pars.add_argument(
+            "-m",
+            "--method",
+            type=str,
+            default="equalSubsegments",
+            help="method of interpolation",
+        )
+        pars.add_argument(
+            "-d", "--dup", type=inkex.Boolean, default=True, help="duplicate endpaths"
+        )
+        pars.add_argument(
+            "--style",
+            type=inkex.Boolean,
+            default=False,
+            help="try interpolation of some style properties",
+        )
+        pars.add_argument(
+            "--zsort",
+            type=inkex.Boolean,
+            default=False,
+            help="use z-order instead of selection order",
+        )
+
+    def effect(self):
+        steps = self.get_steps()
+
+        objectpairs = self.get_copied_path_pairs()
+        if not objectpairs:
+            raise inkex.AbortExtension(_("At least two paths need to be selected"))
+
+        for (elem1, elem2) in objectpairs:
+
+            method = EqualSubsegmentsInterpolator
+            if self.options.method == "firstNodes":
+                method = FirstNodesInterpolator
+
+            path_interpolator = AttributeInterpolator.create_from_attribute(
+                elem1, elem2, "d", method=method
+            )
+            if self.options.style:
+                style_interpolator = StyleInterpolator(elem1, elem2)
+
+            group = self.svg.get_current_layer().add(inkex.Group())
+            for time in steps:
+                interpolated_path = path_interpolator.interpolate(time)
+                new = group.add(inkex.PathElement())
+                new.path = interpolated_path
+                if self.options.style:
+                    interpolated_style = style_interpolator.interpolate(time)
+                    new.style = interpolated_style
+                else:
+                    new.style = copy.deepcopy(elem1.style)
+
+    def get_steps(self):
+        """Returns the interpolation steps as a monotonous array with elements between 0 and 1.
+        0 and 1 are added as first and last elements if the source paths should be duplicated"""
+        exponent = self.options.exponent
+        # if exponent >= 0:
+        #    exponent += 1.0
+        # else:
+        #    exponent = 1.0 / (1.0 - exponent)
+        steps = [
+            ((i + 1) / (self.options.steps + 1.0)) ** exponent
+            for i in range(self.options.steps)
+        ]
+        if self.options.dup:
+            steps = [0] + steps + [1]
+        return steps
+
+    def get_copied_path_pairs(self):
+        """Returns deep copies of pairs of subsequent objects of the
+        current selection, either in z order or in selection order.
+        Objects other than path objects are ignored. Transforms are baked in."""
+        if self.options.zsort:
+            # work around selection order swapping with Live Preview
+            objects = self.svg.selection.rendering_order()
+        else:
+            # use selection order (default)
+            objects = self.svg.selection
+
+        objects = [
+            node for node in objects.values() if isinstance(node, inkex.PathElement)
+        ]
+
+        for node in objects:
+            node.apply_transform()
+
+        objectpairs = pairwise(objects, start=False)
+        return objectpairs
+
+
+if __name__ == "__main__":
+    Interp().run()