Convert to satin internally (3874)

19 files changed, 507 insertions, 404 deletions

diff --git a/lib/elements/__init__.py b/lib/elements/__init__.py
index bcb341e1..e1c35482 100644
--- a/lib/elements/__init__.py
+++ b/lib/elements/__init__.py
@@ -11,4 +11,4 @@ from .image import ImageObject
 from .satin_column import SatinColumn
 from .stroke import Stroke
 from .text import TextObject
-from .utils import node_to_elements, nodes_to_elements
+from .utils.nodes import iterate_nodes, node_to_elements, nodes_to_elements
diff --git a/lib/elements/clone.py b/lib/elements/clone.py
index 5d0ae7fa..bc668bf6 100644
--- a/lib/elements/clone.py
+++ b/lib/elements/clone.py
@@ -76,7 +76,7 @@ class Clone(EmbroideryElement):
 
     def clone_to_elements(self, node: BaseElement) -> List[EmbroideryElement]:
         # Only used in get_cache_key_data, actual embroidery uses nodes_to_elements+iterate_nodes
-        from .utils import node_to_elements
+        from .utils.nodes import node_to_elements
         elements = []
         if node.tag in EMBROIDERABLE_TAGS:
             elements = node_to_elements(node, True)
@@ -141,7 +141,7 @@ class Clone(EmbroideryElement):
         Could possibly be refactored into just a generator - being a context manager is mainly to control the lifecycle of the elements
         that are cloned (again, for testing convenience primarily)
         """
-        from .utils import iterate_nodes, nodes_to_elements
+        from .utils.nodes import iterate_nodes, nodes_to_elements
 
         cloned_nodes = self.resolve_clone()
         try:
diff --git a/lib/elements/satin_column.py b/lib/elements/satin_column.py
index 51a10cad..42b650ed 100644
--- a/lib/elements/satin_column.py
+++ b/lib/elements/satin_column.py
@@ -9,7 +9,7 @@ from copy import deepcopy
 from itertools import chain
 
 import numpy as np
-from inkex import paths
+from inkex import Path
 from shapely import affinity as shaffinity
 from shapely import geometry as shgeo
 from shapely import set_precision
@@ -20,23 +20,16 @@ from ..i18n import _
 from ..metadata import InkStitchMetadata
 from ..stitch_plan import Stitch, StitchGroup
 from ..stitches import running_stitch
-from ..svg import line_strings_to_csp, point_lists_to_csp
+from ..svg import line_strings_to_coordinate_lists
+from ..svg.styles import get_join_style_args
 from ..utils import Point, cache, cut, cut_multiple, offset_points, prng
 from ..utils.param import ParamOption
 from ..utils.threading import check_stop_flag
 from .element import PIXELS_PER_MM, EmbroideryElement, param
+from .utils.stroke_to_satin import convert_path_to_satin
 from .validation import ValidationError, ValidationWarning
 
 
-class TooFewPathsError(ValidationError):
-    name = _("Too few subpaths")
-    description = _("Satin column: Object has too few subpaths.  A satin column should have at least two subpaths (the rails).")
-    steps_to_solve = [
-        _("* Add another subpath (select two rails and do Path > Combine)"),
-        _("* Convert to running stitch or simple satin (Params extension)")
-    ]
-
-
 class NotStitchableError(ValidationError):
     name = _("Not stitchable satin column")
     description = _("A satin column consists out of two rails and one or more rungs. This satin column may have a different setup.")
@@ -77,6 +70,15 @@ class TooManyIntersectionsWarning(ValidationWarning):
     description = _("Satin column: A rung intersects a rail more than once.") + " " + rung_message
 
 
+class StrokeSatinWarning(ValidationWarning):
+    name = _("Simple Satin")
+    description = ("If you need more control over the stitch directions within this satin column, convert it to a real satin path")
+    steps_to_solve = [
+        _('* Select the satin path'),
+        _('* Run Extensions > Ink/Stitch > Tools: Satin > Stroke to Satin')
+    ]
+
+
 class TwoRungsWarning(ValidationWarning):
     name = _("Satin has exactly two rungs")
     description = _("There are exactly two rungs. This may lead to false rail/rung detection.")
@@ -320,7 +322,7 @@ class SatinColumn(EmbroideryElement):
         elif choice == 'both':
             return True, True
         elif choice == 'automatic':
-            rails = [shgeo.LineString(self.flatten_subpath(rail)) for rail in self.rails]
+            rails = [shgeo.LineString(rail) for rail in self.rails]
             if len(rails) == 2:
                 # Sample ten points along the rails.  Compare the distance
                 # between corresponding points on both rails with and without
@@ -598,7 +600,7 @@ class SatinColumn(EmbroideryElement):
         # This isn't used for satins at all, but other parts of the code
         # may need to know the general shape of a satin column.
 
-        return shgeo.MultiLineString(self.flattened_rails)
+        return shgeo.MultiLineString(self.line_string_rails)
 
     @property
     @cache
@@ -615,17 +617,21 @@ class SatinColumn(EmbroideryElement):
 
     @property
     @cache
-    def csp(self):
-        paths = self.parse_path()
-        # exclude subpaths which are just a point
-        paths = [path for path in paths if len(self.flatten_subpath(path)) > 1]
+    def filtered_subpaths(self):
+        paths = [path for path in self.paths if len(path) > 1]
+        if len(paths) == 1:
+            style_args = get_join_style_args(self)
+            new_satin = convert_path_to_satin(paths[0], self.stroke_width, style_args)
+            if new_satin:
+                rails, rungs = new_satin
+                paths = list(rails) + list(rungs)
         return paths
 
     @property
     @cache
     def rails(self):
         """The rails in order, as point lists"""
-        rails = [subpath for i, subpath in enumerate(self.csp) if i in self.rail_indices]
+        rails = [subpath for i, subpath in enumerate(self.filtered_subpaths) if i in self.rail_indices]
         if len(rails) == 2 and self.swap_rails:
             return [rails[1], rails[0]]
         else:
@@ -633,9 +639,9 @@ class SatinColumn(EmbroideryElement):
 
     @property
     @cache
-    def flattened_rails(self):
+    def line_string_rails(self):
         """The rails, as LineStrings."""
-        paths = [set_precision(shgeo.LineString(self.flatten_subpath(rail)), 0.00001) for rail in self.rails]
+        paths = [set_precision(shgeo.LineString(rail), 0.00001) for rail in self.rails]
 
         rails_to_reverse = self._get_rails_to_reverse()
         if paths and rails_to_reverse is not None:
@@ -651,8 +657,9 @@ class SatinColumn(EmbroideryElement):
 
     @property
     @cache
-    def flattened_rungs(self):
-        return tuple(shgeo.LineString(self.flatten_subpath(rung)) for rung in self.rungs)
+    def line_string_rungs(self):
+        """The rungs as LineStrings"""
+        return tuple(shgeo.LineString(rung) for rung in self.rungs)
 
     @property
     @cache
@@ -663,12 +670,12 @@ class SatinColumn(EmbroideryElement):
         rails are expected to have the same number of path nodes.  The path
         nodes, taken in sequential pairs, act in the same way as rungs would.
         """
-        if len(self.csp) == 2:
+        if len(self.filtered_subpaths) == 2:
             # It's an old-style satin column.  To make things easier we'll
             # actually create the implied rungs.
             return self._synthesize_rungs()
         else:
-            return [subpath for i, subpath in enumerate(self.csp) if i not in self.rail_indices]
+            return [subpath for i, subpath in enumerate(self.filtered_subpaths) if i not in self.rail_indices]
 
     @cache
     def _synthesize_rungs(self):
@@ -677,8 +684,7 @@ class SatinColumn(EmbroideryElement):
         equal_length = len(self.rails[0]) == len(self.rails[1])
 
         rails_to_reverse = self._get_rails_to_reverse()
-        for i, rail in enumerate(self.rails):
-            points = self.strip_control_points(rail)
+        for i, points in enumerate(self.rails):
 
             if rails_to_reverse[i]:
                 points = points[::-1]
@@ -699,15 +705,14 @@ class SatinColumn(EmbroideryElement):
             rung = shgeo.LineString((start, end))
             # make it a bit bigger so that it definitely intersects
             rung = shaffinity.scale(rung, 1.1, 1.1).coords
-            rungs.append([[rung[0]] * 3, [rung[1]] * 3])
+            rungs.append(rung)
 
         return rungs
 
     @property
     @cache
     def rail_indices(self):
-        paths = [self.flatten_subpath(subpath) for subpath in self.csp]
-        paths = [shgeo.LineString(path) for path in paths if len(path) > 1]
+        paths = [shgeo.LineString(path) for path in self.filtered_subpaths if len(path) > 1]
         num_paths = len(paths)
 
         # Imagine a satin column as a curvy ladder.
@@ -762,8 +767,8 @@ class SatinColumn(EmbroideryElement):
     def flattened_sections(self):
         """Flatten the rails, cut with the rungs, and return the sections in pairs."""
 
-        rails = list(self.flattened_rails)
-        rungs = self.flattened_rungs
+        rails = list(self.line_string_rails)
+        rungs = list(self.line_string_rungs)
         cut_points = [[], []]
         for rung in rungs:
             intersections = rung.intersection(shgeo.MultiLineString(rails))
@@ -798,27 +803,30 @@ class SatinColumn(EmbroideryElement):
 
         return sections
 
-    def validation_warnings(self):
-        if len(self.csp) == 4:
-            yield TwoRungsWarning(self.flattened_rails[0].interpolate(0.5, normalized=True))
-        elif len(self.csp) == 2:
-            yield NoRungWarning(self.flattened_rails[1].representative_point())
+    def validation_warnings(self):  # noqa: C901
+        paths = self.node.get_path()
+        if any([path.letter == 'Z' for path in paths]):
+            yield ClosedPathWarning(self.line_string_rails[0].coords[0])
+
+        if len(self.paths) == 1:
+            yield StrokeSatinWarning(self.center_line.interpolate(0.5, normalized=True))
+        elif len(self.filtered_subpaths) == 4:
+            yield TwoRungsWarning(self.line_string_rails[0].interpolate(0.5, normalized=True))
+        elif len(self.filtered_subpaths) == 2:
+            yield NoRungWarning(self.line_string_rails[1].representative_point())
             if len(self.rails[0]) != len(self.rails[1]):
-                yield UnequalPointsWarning(self.flattened_rails[0].interpolate(0.5, normalized=True))
-        elif len(self.csp) > 2:
-            for rung in self.flattened_rungs:
-                for rail in self.flattened_rails:
+                yield UnequalPointsWarning(self.line_string_rails[0].interpolate(0.5, normalized=True))
+        elif len(self.filtered_subpaths) > 2:
+            for rung in self.line_string_rungs:
+                for rail in self.line_string_rails:
                     intersection = rung.intersection(rail)
                     if intersection.is_empty:
                         yield DanglingRungWarning(rung.interpolate(0.5, normalized=True))
                     elif not isinstance(intersection, shgeo.Point):
                         yield TooManyIntersectionsWarning(rung.interpolate(0.5, normalized=True))
-        paths = self.node.get_path()
-        if any([path.letter == 'Z' for path in paths]):
-            yield ClosedPathWarning(self.flattened_rails[0].coords[0])
 
     def validation_errors(self):
-        if len(self.flattened_rails) == 0:
+        if len(self.line_string_rails) == 0:
             # Non existing rails can happen due to insane transforms which reduce the size of the
             # satin to zero. The path should still be pointable.
             try:
@@ -826,16 +834,9 @@ class SatinColumn(EmbroideryElement):
             except IndexError:
                 point = (0, 0)
             yield NotStitchableError(point)
-        else:
-            # The node should have exactly two paths with the same number of points - or it should
-            # have two rails and at least one rung
-            if len(self.csp) < 2:
-                yield TooFewPathsError((0, 0))
-            elif len(self.rails) < 2:
-                yield TooFewPathsError(self.flattened_rails[0].representative_point())
 
             if not self.to_stitch_groups():
-                yield NotStitchableError(self.flattened_rails[0].representative_point())
+                yield NotStitchableError(self.line_string_rails[0].representative_point())
 
     def _center_walk_is_odd(self):
         return self.center_walk_underlay and self.center_walk_underlay_repeats % 2 == 1
@@ -843,23 +844,21 @@ class SatinColumn(EmbroideryElement):
     def reverse(self):
         """Return a new SatinColumn like this one but in the opposite direction.
 
-        The path will be flattened and the new satin will contain a new XML
-        node that is not yet in the SVG.
+        The new satin will contain a new XML node that is not yet in the SVG.
         """
-        # flatten the path because you can't just reverse a CSP subpath's elements (I think)
         point_lists = []
 
         for rail in self.rails:
-            point_lists.append(list(reversed(self.flatten_subpath(rail))))
+            point_lists.append(list(reversed(rail)))
 
         for rung in self.rungs:
-            point_lists.append(self.flatten_subpath(rung))
+            point_lists.append(rung)
 
         # If originally there were only two subpaths (no rungs) with same number of points, the rails may now
         # have two rails with different number of points, and still no rungs, let's add one.
 
         if not self.rungs:
-            rails = [shgeo.LineString(reversed(self.flatten_subpath(rail))) for rail in self.rails]
+            rails = [shgeo.LineString(reversed(rail)) for rail in self.rails]
             rails.reverse()
             path_list = rails
 
@@ -871,21 +870,21 @@ class SatinColumn(EmbroideryElement):
             path_list.append(rung)
             return (self._path_list_to_satins(path_list))
 
-        return self._csp_to_satin(point_lists_to_csp(point_lists))
+        return self._coordinates_to_satin(point_lists)
 
     def flip(self):
         """Return a new SatinColumn like this one but with flipped rails.
 
-        The path will be flattened and the new satin will contain a new XML
+        The new satin will contain a new XML
         node that is not yet in the SVG.
         """
-        csp = self.path
+        path = self.filtered_subpaths
 
-        if len(csp) > 1:
+        if len(path) > 1:
             first, second = self.rail_indices
-            csp[first], csp[second] = csp[second], csp[first]
+            path[first], path[second] = path[second], path[first]
 
-        return self._csp_to_satin(csp)
+        return self._coordinates_to_satin(path)
 
     def apply_transform(self):
         """Return a new SatinColumn like this one but with transforms applied.
@@ -894,7 +893,7 @@ class SatinColumn(EmbroideryElement):
         new SatinColumn's node will not be in the SVG document.
         """
 
-        return self._csp_to_satin(self.csp)
+        return self._coordinates_to_satin(self.filtered_subpaths)
 
     def split(self, split_point, cut_points=None):
         """Split a satin into two satins at the specified point
@@ -976,7 +975,7 @@ class SatinColumn(EmbroideryElement):
           rails.  Each element is a list of two rails of type LineString.
         """
 
-        rails = [shgeo.LineString(self.flatten_subpath(rail)) for rail in self.rails]
+        rails = [shgeo.LineString(rail) for rail in self.rails]
 
         path_lists = [[], []]
 
@@ -1009,7 +1008,7 @@ class SatinColumn(EmbroideryElement):
         Each rung is appended to the correct one of the two new satin columns.
         """
 
-        rungs = [shgeo.LineString(self.flatten_subpath(rung)) for rung in self.rungs]
+        rungs = [shgeo.LineString(rung) for rung in self.rungs]
         for path_list in split_rails:
             if path_list is not None:
                 path_list.extend(rung for rung in rungs if path_list[0].intersects(rung) and path_list[1].intersects(rung))
@@ -1059,14 +1058,16 @@ class SatinColumn(EmbroideryElement):
         path_list.append(rung)
 
     def _path_list_to_satins(self, path_list):
-        linestrings = line_strings_to_csp(path_list)
-        if not linestrings:
+        coordinates = line_strings_to_coordinate_lists(path_list)
+        if not coordinates:
             return None
-        return self._csp_to_satin(linestrings)
+        return self._coordinates_to_satin(coordinates)
 
-    def _csp_to_satin(self, csp):
+    def _coordinates_to_satin(self, paths):
         node = deepcopy(self.node)
-        d = paths.CubicSuperPath(csp).to_path()
+        d = ""
+        for path in paths:
+            d += str(Path(path))
         node.set("d", d)
 
         # we've already applied the transform, so get rid of it
@@ -1089,8 +1090,8 @@ class SatinColumn(EmbroideryElement):
         The returned SatinColumn will not be in the SVG document and will have
         its transforms applied.
         """
-        rails = [self.flatten_subpath(rail) for rail in self.rails]
-        other_rails = [satin.flatten_subpath(rail) for rail in satin.rails]
+        rails = self.rails
+        other_rails = satin.rails
 
         if len(rails) != 2 or len(other_rails) != 2:
             # weird non-satin things, give up and don't merge
@@ -1100,8 +1101,8 @@ class SatinColumn(EmbroideryElement):
         rails[0].extend(other_rails[0][1:])
         rails[1].extend(other_rails[1][1:])
 
-        rungs = [self.flatten_subpath(rung) for rung in self.rungs]
-        other_rungs = [satin.flatten_subpath(rung) for rung in satin.rungs]
+        rungs = self.rungs
+        other_rungs = satin.rungs
 
         # add a rung in between the two satins and extend it just a litte to ensure it is crossing the rails
         new_rung = shgeo.LineString([other_rails[0][0], other_rails[1][0]])
@@ -1112,7 +1113,7 @@ class SatinColumn(EmbroideryElement):
 
         rungs = self._get_filtered_rungs(rails, rungs)
 
-        return self._csp_to_satin(point_lists_to_csp(rails + rungs))
+        return self._coordinates_to_satin(line_strings_to_coordinate_lists(rails + rungs))
 
     def _get_filtered_rungs(self, rails, rungs):
         # returns a filtered list of rungs which do intersect the rails exactly twice
@@ -1832,7 +1833,7 @@ class SatinColumn(EmbroideryElement):
     def first_stitch(self):
         if self.start_at_nearest_point:
             return None
-        return shgeo.Point(self.flattened_rails[0].coords[0])
+        return shgeo.Point(self.line_string_rails[0].coords[0])
 
     def start_point(self, last_stitch_group):
         start_point = self._get_command_point('starting_point')
diff --git a/lib/elements/utils.py b/lib/elements/utils/nodes.py
index 43c2387d..0ad765ab 100644
--- a/lib/elements/utils.py
+++ b/lib/elements/utils/nodes.py
@@ -3,27 +3,28 @@
 # Copyright (c) 2010 Authors
 # Licensed under the GNU GPL version 3.0 or later.  See the file LICENSE for details.
 
-from typing import List, Optional, Iterable
+from typing import Iterable, List, Optional
 
 from inkex import BaseElement
 from lxml.etree import Comment
 
-from ..commands import is_command, layer_commands
-from ..debug.debug import sew_stack_enabled
-from ..marker import has_marker
-from ..svg.tags import (CONNECTOR_TYPE, EMBROIDERABLE_TAGS, INKSCAPE_GROUPMODE,
-                        NOT_EMBROIDERABLE_TAGS, SVG_CLIPPATH_TAG, SVG_DEFS_TAG,
-                        SVG_GROUP_TAG, SVG_IMAGE_TAG, SVG_MASK_TAG,
-                        SVG_TEXT_TAG)
-from .clone import Clone, is_clone
-from .element import EmbroideryElement
-from .empty_d_object import EmptyDObject
-from .fill_stitch import FillStitch
-from .image import ImageObject
-from .marker import MarkerObject
-from .satin_column import SatinColumn
-from .stroke import Stroke
-from .text import TextObject
+from ...commands import is_command, layer_commands
+from ...debug.debug import sew_stack_enabled
+from ...marker import has_marker
+from ...svg import PIXELS_PER_MM
+from ...svg.tags import (CONNECTOR_TYPE, EMBROIDERABLE_TAGS,
+                         INKSCAPE_GROUPMODE, NOT_EMBROIDERABLE_TAGS,
+                         SVG_CLIPPATH_TAG, SVG_DEFS_TAG, SVG_GROUP_TAG,
+                         SVG_IMAGE_TAG, SVG_MASK_TAG, SVG_TEXT_TAG)
+from ..clone import Clone, is_clone
+from ..element import EmbroideryElement
+from ..empty_d_object import EmptyDObject
+from ..fill_stitch import FillStitch
+from ..image import ImageObject
+from ..marker import MarkerObject
+from ..satin_column import SatinColumn
+from ..stroke import Stroke
+from ..text import TextObject
 
 
 def node_to_elements(node, clone_to_element=False) -> List[EmbroideryElement]:  # noqa: C901
@@ -42,7 +43,7 @@ def node_to_elements(node, clone_to_element=False) -> List[EmbroideryElement]:
     elif node.tag in EMBROIDERABLE_TAGS or is_clone(node):
         elements: List[EmbroideryElement] = []
 
-        from ..sew_stack import SewStack
+        from ...sew_stack import SewStack
         sew_stack = SewStack(node)
 
         if not sew_stack.sew_stack_only:
@@ -50,7 +51,7 @@ def node_to_elements(node, clone_to_element=False) -> List[EmbroideryElement]:
             if element.fill_color is not None and not element.get_style('fill-opacity', 1) == "0":
                 elements.append(FillStitch(node))
             if element.stroke_color is not None:
-                if element.get_boolean_param("satin_column") and len(element.path) > 1:
+                if element.get_boolean_param("satin_column") and (len(element.path) > 1 or element.stroke_width >= 0.3 / PIXELS_PER_MM):
                     elements.append(SatinColumn(node))
                 elif not is_command(element.node):
                     elements.append(Stroke(node))
diff --git a/lib/elements/utils/stroke_to_satin.py b/lib/elements/utils/stroke_to_satin.py
new file mode 100644
index 00000000..ab14ab18
--- /dev/null
+++ b/lib/elements/utils/stroke_to_satin.py
@@ -0,0 +1,303 @@
+# Authors: see git history
+#
+# Copyright (c) 2025 Authors
+# Licensed under the GNU GPL version 3.0 or later.  See the file LICENSE for details.
+
+from numpy import zeros, convolve, int32, diff, setdiff1d, sign
+from math import degrees, acos
+from ...svg import PIXELS_PER_MM
+
+from ...utils import Point
+from shapely import geometry as shgeo
+from inkex import errormsg
+from ...utils.geometry import remove_duplicate_points
+from shapely.ops import substring
+from shapely.affinity import scale
+from ...i18n import _
+import sys
+
+
+class SelfIntersectionError(Exception):
+    pass
+
+
+def convert_path_to_satin(path, stroke_width, style_args):
+    path = remove_duplicate_points(fix_loop(path))
+
+    if len(path) < 2:
+        # ignore paths with just one point -- they're not visible to the user anyway
+        return None
+
+    sections = list(convert_path_to_satins(path, stroke_width, style_args))
+
+    if sections:
+        joined_satin = list(sections)[0]
+        for satin in sections[1:]:
+            joined_satin = merge(joined_satin, satin)
+        return joined_satin
+    return None
+
+
+def convert_path_to_satins(path, stroke_width, style_args, depth=0):
+    try:
+        rails, rungs = path_to_satin(path, stroke_width, style_args)
+        yield (rails, rungs)
+    except SelfIntersectionError:
+        # The path intersects itself.  Split it in two and try doing the halves
+        # individually.
+
+        if depth >= 20:
+            # At this point we're slicing the path way too small and still
+            # getting nowhere.  Just give up on this section of the path.
+            return
+
+        halves = split_path(path)
+
+        for path in halves:
+            for section in convert_path_to_satins(path, stroke_width, style_args, depth=depth + 1):
+                yield section
+
+
+def split_path(path):
+    linestring = shgeo.LineString(path)
+    halves = [
+        list(substring(linestring, 0, 0.5, normalized=True).coords),
+        list(substring(linestring, 0.5, 1, normalized=True).coords),
+    ]
+
+    return halves
+
+
+def fix_loop(path):
+    if path[0] == path[-1] and len(path) > 1:
+        first = Point.from_tuple(path[0])
+        second = Point.from_tuple(path[1])
+        midpoint = (first + second) / 2
+        midpoint = midpoint.as_tuple()
+
+        return [midpoint] + path[1:] + [path[0], midpoint]
+    else:
+        return path
+
+
+def path_to_satin(path, stroke_width, style_args):
+    if Point(*path[0]).distance(Point(*path[-1])) < 1:
+        raise SelfIntersectionError()
+
+    path = shgeo.LineString(path)
+    distance = stroke_width / 2.0
+
+    try:
+        left_rail = path.offset_curve(-distance, **style_args)
+        right_rail = path.offset_curve(distance, **style_args)
+    except ValueError:
+        # TODO: fix this error automatically
+        # Error reference: https://github.com/inkstitch/inkstitch/issues/964
+        errormsg(_("Ink/Stitch cannot convert your stroke into a satin column. "
+                   "Please break up your path and try again.") + '\n')
+        sys.exit(1)
+
+    if left_rail.geom_type != 'LineString' or right_rail.geom_type != 'LineString':
+        # If the offset curve come out as anything but a LineString, that means the
+        # path intersects itself, when taking its stroke width into consideration.
+        raise SelfIntersectionError()
+
+    rungs = generate_rungs(path, stroke_width, left_rail, right_rail)
+
+    left_rail = list(left_rail.coords)
+    right_rail = list(right_rail.coords)
+
+    return (left_rail, right_rail), rungs
+
+
+def get_scores(path):
+    """Generate an array of "scores" of the sharpness of corners in a path
+
+    A higher score means that there are sharper corners in that section of
+    the path.  We'll divide the path into boxes, with the score in each
+    box indicating the sharpness of corners at around that percentage of
+    the way through the path.  For example, if scores[40] is 100 and
+    scores[45] is 200, then the path has sharper corners at a spot 45%
+    along its length than at a spot 40% along its length.
+    """
+
+    # need 101 boxes in order to encompass percentages from 0% to 100%
+    scores = zeros(101, int32)
+    path_length = path.length
+
+    prev_point = None
+    prev_direction = None
+    length_so_far = 0
+    for point in path.coords:
+        point = Point(*point)
+
+        if prev_point is None:
+            prev_point = point
+            continue
+
+        direction = (point - prev_point).unit()
+
+        if prev_direction is not None:
+            # The dot product of two vectors is |v1| * |v2| * cos(angle).
+            # These are unit vectors, so their magnitudes are 1.
+            cos_angle_between = prev_direction * direction
+
+            # Clamp to the valid range for a cosine.  The above _should_
+            # already be in this range, but floating point inaccuracy can
+            # push it outside the range causing math.acos to throw
+            # ValueError ("math domain error").
+            cos_angle_between = max(-1.0, min(1.0, cos_angle_between))
+
+            angle = abs(degrees(acos(cos_angle_between)))
+
+            # Use the square of the angle, measured in degrees.
+            #
+            # Why the square?  This penalizes bigger angles more than
+            # smaller ones.
+            #
+            # Why degrees?  This is kind of arbitrary but allows us to
+            # use integer math effectively and avoid taking the square
+            # of a fraction between 0 and 1.
+            scores[int(round(length_so_far / path_length * 100.0))] += angle ** 2
+
+        length_so_far += (point - prev_point).length()
+        prev_direction = direction
+        prev_point = point
+
+    return scores
+
+
+def local_minima(array):
+    # from: https://stackoverflow.com/a/9667121/4249120
+    # This finds spots where the curvature (second derivative) is > 0.
+    #
+    # This method has the convenient benefit of choosing points around
+    # 5% before and after a sharp corner such as in a square.
+    return (diff(sign(diff(array))) > 0).nonzero()[0] + 1
+
+
+def generate_rungs(path, stroke_width, left_rail, right_rail):
+    """Create rungs for a satin column.
+
+    Where should we put the rungs along a path?  We want to ensure that the
+    resulting satin matches the original path as closely as possible.  We
+    want to avoid having a ton of rungs that will annoy the user.  We want
+    to ensure that the rungs we choose actually intersect both rails.
+
+    We'll place a few rungs perpendicular to the tangent of the path.
+    Things get pretty tricky at sharp corners.  If we naively place a rung
+    perpendicular to the path just on either side of a sharp corner, the
+    rung may not intersect both paths:
+                   |    |
+    _______________|    |
+                  ______|_
+    ____________________|
+
+    It'd be best to place rungs in the straight sections before and after
+    the sharp corner and allow the satin column to bend the stitches around
+    the corner automatically.
+
+    How can we find those spots?
+
+    The general algorithm below is:
+
+      * assign a "score" to each section of the path based on how sharp its
+        corners are (higher means a sharper corner)
+      * pick spots with lower scores
+    """
+
+    scores = get_scores(path)
+
+    # This is kind of like a 1-dimensional gaussian blur filter.  We want to
+    # avoid the area near a sharp corner, so we spread out its effect for
+    # 5 buckets in either direction.
+    scores = convolve(scores, [1, 2, 4, 8, 16, 8, 4, 2, 1], mode='same')
+
+    # Now we'll find the spots that aren't near corners, whose scores are
+    # low -- the local minima.
+    rung_locations = local_minima(scores)
+
+    # Remove the start and end, because we can't stick a rung there.
+    rung_locations = setdiff1d(rung_locations, [0, 100])
+
+    if len(rung_locations) == 0:
+        # Straight lines won't have local minima, so add a rung in the center.
+        rung_locations = [50]
+
+    rungs = []
+    last_rung_center = None
+
+    for location in rung_locations:
+        # Convert percentage to a fraction so that we can use interpolate's
+        # normalized parameter.
+        location = location / 100.0
+
+        rung_center = path.interpolate(location, normalized=True)
+        rung_center = Point(rung_center.x, rung_center.y)
+
+        # Avoid placing rungs too close together.  This somewhat
+        # arbitrarily rejects the rung if there was one less than 2
+        # millimeters before this one.
+        if last_rung_center is not None and \
+                (rung_center - last_rung_center).length() < 2 * PIXELS_PER_MM:
+            continue
+        else:
+            last_rung_center = rung_center
+
+        # We need to know the tangent of the path's curve at this point.
+        # Pick another point just after this one and subtract them to
+        # approximate a tangent vector.
+        tangent_end = path.interpolate(location + 0.001, normalized=True)
+        tangent_end = Point(tangent_end.x, tangent_end.y)
+        tangent = (tangent_end - rung_center).unit()
+
+        # Rotate 90 degrees left to make a normal vector.
+        normal = tangent.rotate_left()
+
+        # Extend the rungs by an offset value to make sure they will cross the rails
+        offset = normal * (stroke_width / 2) * 1.2
+        rung_start = rung_center + offset
+        rung_end = rung_center - offset
+
+        rung_tuple = (rung_start.as_tuple(), rung_end.as_tuple())
+        rung_linestring = shgeo.LineString(rung_tuple)
+        if (isinstance(rung_linestring.intersection(left_rail), shgeo.Point) and
+                isinstance(rung_linestring.intersection(right_rail), shgeo.Point)):
+            rungs.append(rung_tuple)
+
+    return rungs
+
+
+def merge(section, other_section):
+    """Merge this satin with another satin
+
+    This method expects that the provided satin continues on directly after
+    this one, as would be the case, for example, if the two satins were the
+    result of the split() method.
+
+    Returns a new SatinColumn instance that combines the rails and rungs of
+    this satin and the provided satin.  A rung is added at the end of this
+    satin.
+
+    The returned SatinColumn will not be in the SVG document and will have
+    its transforms applied.
+    """
+    rails, rungs = section
+    other_rails, other_rungs = other_section
+
+    if len(rails) != 2 or len(other_rails) != 2:
+        # weird non-satin things, give up and don't merge
+        return section
+
+    # remove first node of each other rail before merging (avoid duplicated nodes)
+    rails[0].extend(other_rails[0][1:])
+    rails[1].extend(other_rails[1][1:])
+
+    # add a rung in between the two satins and extend it just a litte to ensure it is crossing the rails
+    new_rung = shgeo.LineString([other_rails[0][0], other_rails[1][0]])
+    rungs.append(list(scale(new_rung, 1.2, 1.2).coords))
+
+    # add on the other satin's rungs
+    rungs.extend(other_rungs)
+
+    return (rails, rungs)
diff --git a/lib/extensions/base.py b/lib/extensions/base.py
index 91afbc38..7ec98735 100644
--- a/lib/extensions/base.py
+++ b/lib/extensions/base.py
@@ -7,7 +7,7 @@ import os
 
 import inkex
 
-from ..elements.utils import iterate_nodes, nodes_to_elements
+from ..elements import iterate_nodes, nodes_to_elements
 from ..i18n import _
 from ..metadata import InkStitchMetadata
 from ..svg import generate_unique_id
diff --git a/lib/extensions/lettering_force_lock_stitches.py b/lib/extensions/lettering_force_lock_stitches.py
index 16f81227..a04fac79 100644
--- a/lib/extensions/lettering_force_lock_stitches.py
+++ b/lib/extensions/lettering_force_lock_stitches.py
@@ -6,7 +6,7 @@
 import inkex
 from shapely.geometry import Point
 
-from ..elements.utils import iterate_nodes, nodes_to_elements
+from ..elements import iterate_nodes, nodes_to_elements
 from ..i18n import _
 from ..marker import has_marker
 from ..svg import PIXELS_PER_MM
diff --git a/lib/extensions/params.py b/lib/extensions/params.py
index 0bba13fe..fd4af28f 100755
--- a/lib/extensions/params.py
+++ b/lib/extensions/params.py
@@ -24,6 +24,7 @@ from ..gui import PresetsPanel, PreviewRenderer, WarningPanel
 from ..gui.simulator import SplitSimulatorWindow
 from ..i18n import _
 from ..stitch_plan import stitch_groups_to_stitch_plan
+from ..svg import PIXELS_PER_MM
 from ..svg.tags import EMBROIDERABLE_TAGS
 from ..utils import get_resource_dir
 from ..utils.param import ParamOption
@@ -724,9 +725,9 @@ class Params(InkstitchExtension):
                 if element.fill_color is not None and not element.get_style("fill-opacity", 1) == "0":
                     classes.append(FillStitch)
                 if element.stroke_color is not None:
-                    classes.append(Stroke)
-                    if len(element.path) > 1:
+                    if len(element.path) > 1 or element.stroke_width >= 0.3 * PIXELS_PER_MM:
                         classes.append(SatinColumn)
+                    classes.append(Stroke)
         return classes
 
     def get_nodes_by_class(self):
diff --git a/lib/extensions/stroke_to_satin.py b/lib/extensions/stroke_to_satin.py
index d9bf2ff0..fa360548 100644
--- a/lib/extensions/stroke_to_satin.py
+++ b/lib/extensions/stroke_to_satin.py
@@ -3,28 +3,19 @@
 # Copyright (c) 2010 Authors
 # Licensed under the GNU GPL version 3.0 or later.  See the file LICENSE for details.
 
-import math
-import sys
-from itertools import chain, groupby
+from itertools import chain
 
 import inkex
-import numpy
-from numpy import diff, setdiff1d, sign
 from shapely import geometry as shgeo
-from shapely.ops import substring
 
 from ..elements import SatinColumn, Stroke
+from ..elements.utils.stroke_to_satin import convert_path_to_satin
 from ..i18n import _
-from ..svg import PIXELS_PER_MM, get_correction_transform
-from ..svg.tags import INKSTITCH_ATTRIBS
-from ..utils import Point
+from ..svg import get_correction_transform
+from ..svg.styles import get_join_style_args
 from .base import InkstitchExtension
 
 
-class SelfIntersectionError(Exception):
-    pass
-
-
 class StrokeToSatin(InkstitchExtension):
     """Convert a line to a satin column of the same width."""
 
@@ -36,296 +27,51 @@ class StrokeToSatin(InkstitchExtension):
             inkex.errormsg(_("Please select at least one line to convert to a satin column."))
             return
 
-        if not any(isinstance(item, Stroke) for item in self.elements):
-            # L10N: Convert To Satin extension, user selected one or more objects that were not lines.
-            inkex.errormsg(_("Only simple lines may be converted to satin columns."))
-            return
-
+        satin_converted = False
         for element in self.elements:
-            if not isinstance(element, Stroke):
+            if not isinstance(element, Stroke) and not (isinstance(element, SatinColumn) and len(element.paths) == 1):
                 continue
 
             parent = element.node.getparent()
             index = parent.index(element.node)
             correction_transform = get_correction_transform(element.node)
-            style_args = self.join_style_args(element)
+            style_args = get_join_style_args(element)
             path_style = self.path_style(element)
 
             for path in element.paths:
-                path = self.remove_duplicate_points(self.fix_loop(path))
-
-                if len(path) < 2:
-                    # ignore paths with just one point -- they're not visible to the user anyway
-                    continue
+                satin_paths = convert_path_to_satin(path, element.stroke_width, style_args)
 
-                satins = list(self.convert_path_to_satins(path, element.stroke_width, style_args, path_style))
+                if satin_paths is not None:
+                    rails, rungs = list(satin_paths)
+                    rungs = self.filtered_rungs(rails, rungs)
 
-                if satins:
-                    joined_satin = satins[0]
-                    for satin in satins[1:]:
-                        joined_satin = joined_satin.merge(satin)
-
-                    joined_satin.node.set('transform', correction_transform)
-                    parent.insert(index, joined_satin.node)
+                    path_element = self.satin_to_svg_node(rails, rungs)
+                    path_element.set('id', self.uniqueId("path"))
+                    path_element.set('transform', correction_transform)
+                    path_element.set('style', path_style)
+                    parent.insert(index, path_element)
 
             element.node.delete()
+            satin_converted = True
 
-    def convert_path_to_satins(self, path, stroke_width, style_args, path_style, depth=0):
-        try:
-            rails, rungs = self.path_to_satin(path, stroke_width, style_args)
-            yield SatinColumn(self.satin_to_svg_node(rails, rungs, path_style))
-        except SelfIntersectionError:
-            # The path intersects itself.  Split it in two and try doing the halves
-            # individually.
-
-            if depth >= 20:
-                # At this point we're slicing the path way too small and still
-                # getting nowhere.  Just give up on this section of the path.
-                return
-
-            halves = self.split_path(path)
-
-            for path in halves:
-                for satin in self.convert_path_to_satins(path, stroke_width, style_args, path_style, depth=depth + 1):
-                    yield satin
-
-    def split_path(self, path):
-        linestring = shgeo.LineString(path)
-        halves = [
-            list(substring(linestring, 0, 0.5, normalized=True).coords),
-            list(substring(linestring, 0.5, 1, normalized=True).coords),
-        ]
-
-        return halves
-
-    def fix_loop(self, path):
-        if path[0] == path[-1] and len(path) > 1:
-            first = Point.from_tuple(path[0])
-            second = Point.from_tuple(path[1])
-            midpoint = (first + second) / 2
-            midpoint = midpoint.as_tuple()
-
-            return [midpoint] + path[1:] + [path[0], midpoint]
-        else:
-            return path
-
-    def remove_duplicate_points(self, path):
-        path = [[round(coord, 4) for coord in point] for point in path]
-        return [point for point, repeats in groupby(path)]
-
-    def join_style_args(self, element):
-        """Convert svg line join style to shapely offset_curve arguments."""
-
-        args = {
-            # mitre is the default per SVG spec
-            'join_style': shgeo.JOIN_STYLE.mitre
-        }
-
-        element_join_style = element.get_style('stroke-linejoin')
-
-        if element_join_style is not None:
-            if element_join_style == "miter":
-                args['join_style'] = shgeo.JOIN_STYLE.mitre
-
-                # 4 is the default per SVG spec
-                miter_limit = float(element.get_style('stroke-miterlimit', 4))
-                args['mitre_limit'] = miter_limit
-            elif element_join_style == "bevel":
-                args['join_style'] = shgeo.JOIN_STYLE.bevel
-            elif element_join_style == "round":
-                args['join_style'] = shgeo.JOIN_STYLE.round
-
-        return args
-
-    def path_to_satin(self, path, stroke_width, style_args):
-        if Point(*path[0]).distance(Point(*path[-1])) < 1:
-            raise SelfIntersectionError()
-
-        path = shgeo.LineString(path)
-        distance = stroke_width / 2.0
-
-        try:
-            left_rail = path.offset_curve(-distance, **style_args)
-            right_rail = path.offset_curve(distance, **style_args)
-        except ValueError:
-            # TODO: fix this error automatically
-            # Error reference: https://github.com/inkstitch/inkstitch/issues/964
-            inkex.errormsg(_("Ink/Stitch cannot convert your stroke into a satin column. "
-                             "Please break up your path and try again.") + '\n')
-            sys.exit(1)
-
-        if left_rail.geom_type != 'LineString' or right_rail.geom_type != 'LineString':
-            # If the offset curve come out as anything but a LineString, that means the
-            # path intersects itself, when taking its stroke width into consideration.
-            raise SelfIntersectionError()
-
-        rungs = self.generate_rungs(path, stroke_width, left_rail, right_rail)
-
-        left_rail = list(left_rail.coords)
-        right_rail = list(right_rail.coords)
-
-        return (left_rail, right_rail), rungs
-
-    def get_scores(self, path):
-        """Generate an array of "scores" of the sharpness of corners in a path
-
-        A higher score means that there are sharper corners in that section of
-        the path.  We'll divide the path into boxes, with the score in each
-        box indicating the sharpness of corners at around that percentage of
-        the way through the path.  For example, if scores[40] is 100 and
-        scores[45] is 200, then the path has sharper corners at a spot 45%
-        along its length than at a spot 40% along its length.
-        """
-
-        # need 101 boxes in order to encompass percentages from 0% to 100%
-        scores = numpy.zeros(101, numpy.int32)
-        path_length = path.length
-
-        prev_point = None
-        prev_direction = None
-        length_so_far = 0
-        for point in path.coords:
-            point = Point(*point)
-
-            if prev_point is None:
-                prev_point = point
-                continue
-
-            direction = (point - prev_point).unit()
-
-            if prev_direction is not None:
-                # The dot product of two vectors is |v1| * |v2| * cos(angle).
-                # These are unit vectors, so their magnitudes are 1.
-                cos_angle_between = prev_direction * direction
-
-                # Clamp to the valid range for a cosine.  The above _should_
-                # already be in this range, but floating point inaccuracy can
-                # push it outside the range causing math.acos to throw
-                # ValueError ("math domain error").
-                cos_angle_between = max(-1.0, min(1.0, cos_angle_between))
-
-                angle = abs(math.degrees(math.acos(cos_angle_between)))
-
-                # Use the square of the angle, measured in degrees.
-                #
-                # Why the square?  This penalizes bigger angles more than
-                # smaller ones.
-                #
-                # Why degrees?  This is kind of arbitrary but allows us to
-                # use integer math effectively and avoid taking the square
-                # of a fraction between 0 and 1.
-                scores[int(round(length_so_far / path_length * 100.0))] += angle ** 2
-
-            length_so_far += (point - prev_point).length()
-            prev_direction = direction
-            prev_point = point
-
-        return scores
-
-    def local_minima(self, array):
-        # from: https://stackoverflow.com/a/9667121/4249120
-        # This finds spots where the curvature (second derivative) is > 0.
-        #
-        # This method has the convenient benefit of choosing points around
-        # 5% before and after a sharp corner such as in a square.
-        return (diff(sign(diff(array))) > 0).nonzero()[0] + 1
-
-    def generate_rungs(self, path, stroke_width, left_rail, right_rail):
-        """Create rungs for a satin column.
-
-        Where should we put the rungs along a path?  We want to ensure that the
-        resulting satin matches the original path as closely as possible.  We
-        want to avoid having a ton of rungs that will annoy the user.  We want
-        to ensure that the rungs we choose actually intersect both rails.
-
-        We'll place a few rungs perpendicular to the tangent of the path.
-        Things get pretty tricky at sharp corners.  If we naively place a rung
-        perpendicular to the path just on either side of a sharp corner, the
-        rung may not intersect both paths:
-                       |    |
-        _______________|    |
-                      ______|_
-        ____________________|
-
-        It'd be best to place rungs in the straight sections before and after
-        the sharp corner and allow the satin column to bend the stitches around
-        the corner automatically.
-
-        How can we find those spots?
-
-        The general algorithm below is:
-
-          * assign a "score" to each section of the path based on how sharp its
-            corners are (higher means a sharper corner)
-          * pick spots with lower scores
-        """
-
-        scores = self.get_scores(path)
-
-        # This is kind of like a 1-dimensional gaussian blur filter.  We want to
-        # avoid the area near a sharp corner, so we spread out its effect for
-        # 5 buckets in either direction.
-        scores = numpy.convolve(scores, [1, 2, 4, 8, 16, 8, 4, 2, 1], mode='same')
-
-        # Now we'll find the spots that aren't near corners, whose scores are
-        # low -- the local minima.
-        rung_locations = self.local_minima(scores)
-
-        # Remove the start and end, because we can't stick a rung there.
-        rung_locations = setdiff1d(rung_locations, [0, 100])
-
-        if len(rung_locations) == 0:
-            # Straight lines won't have local minima, so add a rung in the center.
-            rung_locations = [50]
-
-        rungs = []
-        last_rung_center = None
-
-        for location in rung_locations:
-            # Convert percentage to a fraction so that we can use interpolate's
-            # normalized parameter.
-            location = location / 100.0
-
-            rung_center = path.interpolate(location, normalized=True)
-            rung_center = Point(rung_center.x, rung_center.y)
-
-            # Avoid placing rungs too close together.  This somewhat
-            # arbitrarily rejects the rung if there was one less than 2
-            # millimeters before this one.
-            if last_rung_center is not None and \
-                    (rung_center - last_rung_center).length() < 2 * PIXELS_PER_MM:
-                continue
-            else:
-                last_rung_center = rung_center
-
-            # We need to know the tangent of the path's curve at this point.
-            # Pick another point just after this one and subtract them to
-            # approximate a tangent vector.
-            tangent_end = path.interpolate(location + 0.001, normalized=True)
-            tangent_end = Point(tangent_end.x, tangent_end.y)
-            tangent = (tangent_end - rung_center).unit()
-
-            # Rotate 90 degrees left to make a normal vector.
-            normal = tangent.rotate_left()
-
-            # Extend the rungs by an offset value to make sure they will cross the rails
-            offset = normal * (stroke_width / 2) * 1.2
-            rung_start = rung_center + offset
-            rung_end = rung_center - offset
-
-            rung_tuple = (rung_start.as_tuple(), rung_end.as_tuple())
-            rung_linestring = shgeo.LineString(rung_tuple)
-            if (isinstance(rung_linestring.intersection(left_rail), shgeo.Point) and
-                    isinstance(rung_linestring.intersection(right_rail), shgeo.Point)):
-                rungs.append(rung_tuple)
+        if not satin_converted:
+            # L10N: Convert To Satin extension, user selected only objects that were not lines.
+            inkex.errormsg(_("Only simple lines may be converted to satin columns."))
 
-        return rungs
+    def filtered_rungs(self, rails, rungs):
+        rails = shgeo.MultiLineString(rails)
+        filtered_rungs = []
+        for rung in shgeo.MultiLineString(rungs).geoms:
+            intersection = rung.intersection(rails)
+            if intersection.geom_type == "MultiPoint" and len(intersection.geoms) == 2:
+                filtered_rungs.append(list(rung.coords))
+        return filtered_rungs
 
     def path_style(self, element):
         color = element.get_style('stroke', '#000000')
         return "stroke:%s;stroke-width:1px;fill:none" % (color)
 
-    def satin_to_svg_node(self, rails, rungs, path_style):
+    def satin_to_svg_node(self, rails, rungs):
         d = ""
         for path in chain(rails, rungs):
             d += "M"
@@ -333,9 +79,8 @@ class StrokeToSatin(InkstitchExtension):
                 d += "%s,%s " % (x, y)
             d += " "
 
-        return inkex.PathElement(attrib={
-            "id": self.uniqueId("path"),
-            "style": path_style,
+        path_element = inkex.PathElement(attrib={
             "d": d,
-            INKSTITCH_ATTRIBS['satin_column']: "true",
         })
+        path_element.set("inkstitch:satin_column", True)
+        return path_element
diff --git a/lib/gui/lettering/main_panel.py b/lib/gui/lettering/main_panel.py
index fc6d16ad..1766516e 100644
--- a/lib/gui/lettering/main_panel.py
+++ b/lib/gui/lettering/main_panel.py
@@ -10,7 +10,7 @@ import inkex
 import wx
 import wx.adv
 
-from ...elements.utils import iterate_nodes, nodes_to_elements
+from ...elements import iterate_nodes, nodes_to_elements
 from ...i18n import _
 from ...lettering import FontError, get_font_list
 from ...lettering.categories import FONT_CATEGORIES
diff --git a/lib/gui/satin_multicolor/main_panel.py b/lib/gui/satin_multicolor/main_panel.py
index 8c4bbaf9..6ecb30c4 100644
--- a/lib/gui/satin_multicolor/main_panel.py
+++ b/lib/gui/satin_multicolor/main_panel.py
@@ -9,7 +9,7 @@ import inkex
 import wx
 import wx.adv
 
-from ...elements.utils import nodes_to_elements
+from ...elements import nodes_to_elements
 from ...exceptions import InkstitchException, format_uncaught_exception
 from ...i18n import _
 from ...stitch_plan import stitch_groups_to_stitch_plan
diff --git a/lib/marker.py b/lib/marker.py
index cd700674..bf74c02e 100644
--- a/lib/marker.py
+++ b/lib/marker.py
@@ -97,7 +97,7 @@ def get_marker_elements_cache_key_data(node, marker):
 
     marker_elements['fill'] = [shape.wkt for shape in marker_elements['fill']]
     marker_elements['stroke'] = [shape.wkt for shape in marker_elements['stroke']]
-    marker_elements['satin'] = [satin.csp for satin in marker_elements['satin']]
+    marker_elements['satin'] = [satin.filtered_subpaths for satin in marker_elements['satin']]
 
     return marker_elements
 
diff --git a/lib/svg/__init__.py b/lib/svg/__init__.py
index b17a37f0..6694d534 100644
--- a/lib/svg/__init__.py
+++ b/lib/svg/__init__.py
@@ -4,8 +4,10 @@
 # Licensed under the GNU GPL version 3.0 or later.  See the file LICENSE for details.
 
 from .guides import get_guides
-from .path import apply_transforms, get_node_transform, get_correction_transform, line_strings_to_csp, point_lists_to_csp, line_strings_to_path
-from .path import apply_transforms, get_node_transform, get_correction_transform, line_strings_to_csp, point_lists_to_csp
+from .path import (apply_transforms, get_correction_transform,
+                   get_node_transform, line_strings_to_coordinate_lists,
+                   line_strings_to_csp, line_strings_to_path,
+                   point_lists_to_csp)
 from .rendering import color_block_to_point_lists, render_stitch_plan
-from .svg import get_document, generate_unique_id
-from .units import *
\ No newline at end of file
+from .svg import generate_unique_id, get_document
+from .units import *
diff --git a/lib/svg/path.py b/lib/svg/path.py
index 5e6e7007..a7c7b1ca 100644
--- a/lib/svg/path.py
+++ b/lib/svg/path.py
@@ -85,6 +85,19 @@ def get_correction_transform(node: inkex.BaseElement, child=False) -> str:
     return str(transform)
 
 
+def line_strings_to_coordinate_lists(line_strings):
+    try:
+        # This lets us accept a MultiLineString or a list.
+        line_strings = line_strings.geoms
+    except AttributeError:
+        pass
+
+    if line_strings is None:
+        return None
+
+    return [list(ls.coords) for ls in line_strings]
+
+
 def line_strings_to_csp(line_strings):
     try:
         # This lets us accept a MultiLineString or a list.
diff --git a/lib/svg/styles.py b/lib/svg/styles.py
new file mode 100644
index 00000000..c3daaf19
--- /dev/null
+++ b/lib/svg/styles.py
@@ -0,0 +1,31 @@
+# Authors: see git history
+#
+# Copyright (c) 2025 Authors
+# Licensed under the GNU GPL version 3.0 or later.  See the file LICENSE for details.
+
+from shapely.geometry import JOIN_STYLE
+
+
+def get_join_style_args(element):
+    """Convert svg line join style to shapely offset_curve arguments."""
+
+    args = {
+        # mitre is the default per SVG spec
+        'join_style': JOIN_STYLE.mitre
+    }
+
+    element_join_style = element.get_style('stroke-linejoin')
+
+    if element_join_style is not None:
+        if element_join_style == "miter":
+            args['join_style'] = JOIN_STYLE.mitre
+
+            # 4 is the default per SVG spec
+            miter_limit = float(element.get_style('stroke-miterlimit', 4))
+            args['mitre_limit'] = miter_limit
+        elif element_join_style == "bevel":
+            args['join_style'] = JOIN_STYLE.bevel
+        elif element_join_style == "round":
+            args['join_style'] = JOIN_STYLE.round
+
+    return args
diff --git a/lib/utils/geometry.py b/lib/utils/geometry.py
index 39bbd963..39a1f3fb 100644
--- a/lib/utils/geometry.py
+++ b/lib/utils/geometry.py
@@ -5,6 +5,7 @@
 
 import math
 import typing
+from itertools import groupby
 
 import numpy
 from shapely.geometry import (GeometryCollection, LinearRing, LineString,
@@ -242,6 +243,11 @@ def offset_points(pos1, pos2, offset_px, offset_proportional):
     return out1, out2
 
 
+def remove_duplicate_points(path):
+    path = [[round(coord, 4) for coord in point] for point in path]
+    return [point for point, repeats in groupby(path)]
+
+
 class Point:
     def __init__(self, x: typing.Union[float, numpy.float64], y: typing.Union[float, numpy.float64]):
         self.x = float(x)
diff --git a/tests/test_elements_utils.py b/tests/test_elements_utils.py
index 2c0a64eb..0acc20a8 100644
--- a/tests/test_elements_utils.py
+++ b/tests/test_elements_utils.py
@@ -2,7 +2,7 @@ from inkex import Group, Rectangle, Style
 from inkex.tester import TestCase
 from inkex.tester.svg import svg
 
-from lib.elements import FillStitch, utils
+from lib.elements import FillStitch, nodes_to_elements, iterate_nodes
 
 from .utils import element_count
 
@@ -30,7 +30,7 @@ class ElementsUtilsTest(TestCase):
             "height": "10",
         }))
 
-        elements = utils.nodes_to_elements(utils.iterate_nodes(g))
+        elements = nodes_to_elements(iterate_nodes(g))
         self.assertEqual(len(elements), element_count())
         self.assertEqual(type(elements[0]), FillStitch)
         self.assertEqual(elements[0].node, rect)
@@ -43,7 +43,7 @@ class ElementsUtilsTest(TestCase):
             "height": "10"
         }))
 
-        elements = utils.nodes_to_elements(utils.iterate_nodes(rect))
+        elements = nodes_to_elements(iterate_nodes(rect))
         self.assertEqual(len(elements), element_count())
         self.assertEqual(type(elements[0]), FillStitch)
         self.assertEqual(elements[0].node, rect)
@@ -51,5 +51,5 @@ class ElementsUtilsTest(TestCase):
         # Now make the element hidden: It shouldn't return an element
         rect.style = rect.style + Style({"display": "none"})
 
-        elements = utils.nodes_to_elements(utils.iterate_nodes(rect))
+        elements = nodes_to_elements(iterate_nodes(rect))
         self.assertEqual(len(elements), 0)
diff --git a/tests/test_output.py b/tests/test_output.py
index afccca7e..9ed63602 100644
--- a/tests/test_output.py
+++ b/tests/test_output.py
@@ -3,7 +3,7 @@ from inkex.tester import TestCase
 from inkex.tester.svg import svg
 
 from lib import output
-from lib.elements.utils import node_to_elements
+from lib.elements import node_to_elements
 from lib.stitch_plan.stitch_plan import stitch_groups_to_stitch_plan
 from lib.svg.tags import INKSTITCH_ATTRIBS
 
diff --git a/tests/test_threads_color.py b/tests/test_threads_color.py
index 075312e6..3e84e8c4 100644
--- a/tests/test_threads_color.py
+++ b/tests/test_threads_color.py
@@ -2,7 +2,7 @@ from inkex import LinearGradient, Rectangle, Stop, SvgDocumentElement
 from inkex.tester.svg import svg
 
 from lib.elements import EmbroideryElement
-from lib.elements.utils import node_to_elements
+from lib.elements import node_to_elements
 from lib.threads.color import ThreadColor