kopia lustrzana https://github.com/inkstitch/inkstitch
290 wiersze
11 KiB
Python
290 wiersze
11 KiB
Python
import inkex
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from shapely import geometry as shgeo
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from itertools import chain, groupby
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import numpy
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from numpy import diff, sign, setdiff1d
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import math
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from copy import deepcopy
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from .base import InkstitchExtension
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from ..svg.tags import SVG_PATH_TAG
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from ..svg import get_correction_transform, PIXELS_PER_MM
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from ..elements import Stroke
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from ..utils import Point
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class SelfIntersectionError(Exception):
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pass
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class ConvertToSatin(InkstitchExtension):
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"""Convert a line to a satin column of the same width."""
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def effect(self):
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if not self.get_elements():
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return
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if not self.selected:
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inkex.errormsg(_("Please select at least one line to convert to a satin column."))
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return
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if not all(isinstance(item, Stroke) for item in self.elements):
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# L10N: Convert To Satin extension, user selected one or more objects that were not lines.
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inkex.errormsg(_("Only simple lines may be converted to satin columns."))
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return
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for element in self.elements:
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parent = element.node.getparent()
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index = parent.index(element.node)
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correction_transform = get_correction_transform(element.node)
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style_args = self.join_style_args(element)
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for path in element.paths:
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path = self.remove_duplicate_points(path)
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if len(path) < 2:
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# ignore paths with just one point -- they're not visible to the user anyway
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continue
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self.fix_loop(path)
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try:
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rails, rungs = self.path_to_satin(path, element.stroke_width, style_args)
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except SelfIntersectionError:
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inkex.errormsg(_("Cannot convert %s to a satin column because it intersects itself. Try breaking it up into multiple paths.") % element.node.get('id'))
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# revert any changes we've made
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self.document = deepcopy(self.original_document)
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return
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parent.insert(index, self.satin_to_svg_node(rails, rungs, correction_transform))
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parent.remove(element.node)
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def fix_loop(self, path):
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if path[0] == path[-1]:
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# Looping paths seem to confuse shapely's parallel_offset(). It loses track
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# of where the start and endpoint is, even if the user explicitly breaks the
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# path. I suspect this is because parallel_offset() uses buffer() under the
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# hood.
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#
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# To work around this we'll introduce a tiny gap by nudging the starting point
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# toward the next point slightly.
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start = Point(*path[0])
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next = Point(*path[1])
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direction = (next - start).unit()
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start += 0.01 * direction
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path[0] = start.as_tuple()
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def remove_duplicate_points(self, path):
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return [point for point, repeats in groupby(path)]
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def join_style_args(self, element):
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"""Convert svg line join style to shapely parallel offset arguments."""
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args = {
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'join_style': shgeo.JOIN_STYLE.round
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}
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element_join_style = element.get_style('stroke-linejoin')
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if element_join_style is not None:
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if element_join_style == "miter":
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args['join_style'] = shgeo.JOIN_STYLE.mitre
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# 4 is the default per SVG spec
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miter_limit = float(element.get_style('stroke-miterlimit', 4))
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args['mitre_limit'] = miter_limit
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elif element_join_style == "bevel":
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args['join_style'] = shgeo.JOIN_STYLE.bevel
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return args
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def path_to_satin(self, path, stroke_width, style_args):
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path = shgeo.LineString(path)
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left_rail = path.parallel_offset(stroke_width / 2.0, 'left', **style_args)
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right_rail = path.parallel_offset(stroke_width / 2.0, 'right', **style_args)
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if not isinstance(left_rail, shgeo.LineString) or \
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not isinstance(right_rail, shgeo.LineString):
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# If the parallel offsets come out as anything but a LineString, that means the
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# path intersects itself, when taking its stroke width into consideration. See
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# the last example for parallel_offset() in the Shapely documentation:
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# https://shapely.readthedocs.io/en/latest/manual.html#object.parallel_offset
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raise SelfIntersectionError()
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# for whatever reason, shapely returns a right-side offset's coordinates in reverse
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left_rail = list(left_rail.coords)
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right_rail = list(reversed(right_rail.coords))
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rungs = self.generate_rungs(path, stroke_width)
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return (left_rail, right_rail), rungs
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def get_scores(self, path):
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"""Generate an array of "scores" of the sharpness of corners in a path
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A higher score means that there are sharper corners in that section of
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the path. We'll divide the path into boxes, with the score in each
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box indicating the sharpness of corners at around that percentage of
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the way through the path. For example, if scores[40] is 100 and
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scores[45] is 200, then the path has sharper corners at a spot 45%
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along its length than at a spot 40% along its length.
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"""
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# need 101 boxes in order to encompass percentages from 0% to 100%
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scores = numpy.zeros(101, numpy.int32)
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path_length = path.length
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prev_point = None
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prev_direction = None
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length_so_far = 0
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for point in path.coords:
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point = Point(*point)
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if prev_point is None:
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prev_point = point
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continue
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direction = (point - prev_point).unit()
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if prev_direction is not None:
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# The dot product of two vectors is |v1| * |v2| * cos(angle).
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# These are unit vectors, so their magnitudes are 1.
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cos_angle_between = prev_direction * direction
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angle = abs(math.degrees(math.acos(cos_angle_between)))
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# Use the square of the angle, measured in degrees.
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#
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# Why the square? This penalizes bigger angles more than
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# smaller ones.
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#
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# Why degrees? This is kind of arbitrary but allows us to
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# use integer math effectively and avoid taking the square
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# of a fraction between 0 and 1.
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scores[int(round(length_so_far / path_length * 100.0))] += angle ** 2
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length_so_far += (point - prev_point).length()
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prev_direction = direction
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prev_point = point
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return scores
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def local_minima(self, array):
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# from: https://stackoverflow.com/a/9667121/4249120
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# This finds spots where the curvature (second derivative) is > 0.
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#
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# This method has the convenient benefit of choosing points around
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# 5% before and after a sharp corner such as in a square.
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return (diff(sign(diff(array))) > 0).nonzero()[0] + 1
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def generate_rungs(self, path, stroke_width):
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"""Create rungs for a satin column.
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Where should we put the rungs along a path? We want to ensure that the
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resulting satin matches the original path as closely as possible. We
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want to avoid having a ton of rungs that will annoy the user. We want
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to ensure that the rungs we choose actually intersect both rails.
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We'll place a few rungs perpendicular to the tangent of the path.
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Things get pretty tricky at sharp corners. If we naively place a rung
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perpendicular to the path just on either side of a sharp corner, the
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rung may not intersect both paths:
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_______________| |
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______|_
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____________________|
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It'd be best to place rungs in the straight sections before and after
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the sharp corner and allow the satin column to bend the stitches around
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the corner automatically.
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How can we find those spots?
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The general algorithm below is:
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* assign a "score" to each section of the path based on how sharp its
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corners are (higher means a sharper corner)
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* pick spots with lower scores
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"""
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scores = self.get_scores(path)
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# This is kind of like a 1-dimensional gaussian blur filter. We want to
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# avoid the area near a sharp corner, so we spread out its effect for
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# 5 buckets in either direction.
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scores = numpy.convolve(scores, [1, 2, 4, 8, 16, 8, 4, 2, 1], mode='same')
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# Now we'll find the spots that aren't near corners, whose scores are
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# low -- the local minima.
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rung_locations = self.local_minima(scores)
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# Remove the start and end, because we can't stick a rung there.
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rung_locations = setdiff1d(rung_locations, [0, 100])
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if len(rung_locations) == 0:
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# Straight lines won't have local minima, so add a rung in the center.
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rung_locations = [50]
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rungs = []
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last_rung_center = None
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for location in rung_locations:
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# Convert percentage to a fraction so that we can use interpolate's
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# normalized parameter.
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location = location / 100.0
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rung_center = path.interpolate(location, normalized=True)
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rung_center = Point(rung_center.x, rung_center.y)
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# Avoid placing rungs too close together. This somewhat
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# arbitrarily rejects the rung if there was one less than 2
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# millimeters before this one.
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if last_rung_center is not None and \
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(rung_center - last_rung_center).length() < 2 * PIXELS_PER_MM:
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continue
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else:
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last_rung_center = rung_center
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# We need to know the tangent of the path's curve at this point.
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# Pick another point just after this one and subtract them to
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# approximate a tangent vector.
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tangent_end = path.interpolate(location + 0.001, normalized=True)
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tangent_end = Point(tangent_end.x, tangent_end.y)
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tangent = (tangent_end - rung_center).unit()
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# Rotate 90 degrees left to make a normal vector.
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normal = tangent.rotate_left()
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# Travel 75% of the stroke width left and right to make the rung's
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# endpoints. This means the rung's length is 150% of the stroke
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# width.
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offset = normal * stroke_width * 0.75
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rung_start = rung_center + offset
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rung_end = rung_center - offset
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rungs.append((rung_start.as_tuple(), rung_end.as_tuple()))
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return rungs
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def satin_to_svg_node(self, rails, rungs, correction_transform):
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d = ""
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for path in chain(rails, rungs):
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d += "M"
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for x, y in path:
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d += "%s,%s " % (x, y)
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d += " "
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return inkex.etree.Element(SVG_PATH_TAG,
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{
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"id": self.uniqueId("path"),
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"style": "stroke:#000000;stroke-width:1px;fill:none",
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"transform": correction_transform,
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"d": d,
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"embroider_satin_column": "true",
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}
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)
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