inkscape/share/extensions/path_envelope.py

# coding=utf-8
#
# Copyright (C) 2005 Aaron Spike, aaron@ekips.org
#
# 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 inkex
from inkex.transforms import DirectedLineSegment
from inkex.localization import inkex_gettext as _
from operator import truediv


class Envelope(inkex.EffectExtension):
    """Distort a path/group of paths to a second path"""

    def effect(self):
        if len(self.svg.selection) != 2:
            raise inkex.AbortExtension(_("You must select two objects only."))

        obj, envelope = self.svg.selection

        if isinstance(obj, (inkex.PathElement, inkex.Group)):
            if isinstance(envelope, inkex.PathElement):
                # Get bounding box plus any extra composed transform of parents.
                bbox = obj.bounding_box(obj.getparent().composed_transform())

                # distill trafo into four node points
                path = envelope.path.transform(
                    envelope.composed_transform()
                ).to_superpath()
                tbox = self.envelope_box_from_path(path)
            else:
                if isinstance(envelope, inkex.Group):
                    raise inkex.AbortExtension(
                        _(
                            "The second selected object is a group, not a"
                            " path.\nTry using Object->Ungroup."
                        )
                    )
                raise inkex.AbortExtension(
                    _(
                        "The second selected object is not a path.\nTry using"
                        " the procedure Path->Object to Path."
                    )
                )
        else:
            raise inkex.AbortExtension(
                _(
                    "The first selected object is neither a path nor a group.\nTry using"
                    " the procedure Path->Object to Path."
                )
            )

        self.process_object(obj, tbox, bbox)

    def envelope_box_from_path(self, envelope_path):
        if len(envelope_path) < 1 or len(envelope_path[0]) < 4:
            raise inkex.AbortExtension(
                _("Second selected path is too short. Must be four or more nodes.")
            )
        trafo = [[(csp[1][0], csp[1][1]) for csp in subs] for subs in envelope_path][0][
            :4
        ]
        # vectors pointing away from the trafo origin
        tbox = [
            DirectedLineSegment(trafo[0], trafo[1]),
            DirectedLineSegment(trafo[1], trafo[2]),
            DirectedLineSegment(trafo[3], trafo[2]),
            DirectedLineSegment(trafo[0], trafo[3]),
        ]
        vects = [segment.vector for segment in tbox]
        if (
            0.0
            == vects[0].cross(vects[1])
            == vects[1].cross(vects[2])
            == vects[2].cross(vects[3])
        ):
            raise inkex.AbortExtension(
                _("The points for the selected envelope must not all be in a line.")
            )
        return tbox

    def process_object(self, obj, tbox, bbox):
        if isinstance(obj, inkex.PathElement):
            self.process_path(obj, tbox, bbox)
        elif isinstance(obj, inkex.Group):
            self.process_group(obj, tbox, bbox)

    def process_group(self, group, tbox, bbox):
        """Go through all groups to process all paths inside them"""
        for node in group:
            self.process_object(node, tbox, bbox)

    def process_path(self, element, tbox, bbox):
        # Get out path's absolute and root coordinates, so obj and envelope
        # are always in the same coordinate system.
        points = (
            element.path.to_absolute()
            .transform(element.composed_transform())
            .to_superpath()
        )

        for subs in points:
            for csp in subs:
                csp[0] = self.transform_point(tbox, bbox, *csp[0])
                csp[1] = self.transform_point(tbox, bbox, *csp[1])
                csp[2] = self.transform_point(tbox, bbox, *csp[2])

        # Put the modified path back, undo the root transformation
        element.path = points.to_path().transform(-element.composed_transform())

    @staticmethod
    def transform_point(tbox, bbox, x, y):
        """Transform algorithm thanks to Jose Hevia (freon)"""
        vector = (x, y) - bbox.minimum
        xratio, yratio = map(truediv, vector, (bbox.width, bbox.height))
        horz = DirectedLineSegment(
            tbox[0].point_at_ratio(xratio), tbox[2].point_at_ratio(xratio)
        )
        vert = DirectedLineSegment(
            tbox[3].point_at_ratio(yratio), tbox[1].point_at_ratio(yratio)
        )
        denom = horz.vector.cross(vert.vector)
        if denom == 0.0:
            # Degenerate cases of intersecting envelope edges
            if horz.length == 0.0:
                return horz.start
            if vert.length == 0.0:
                return vert.start
            # Here we should know that the lines share a start or end point.
            if horz.vector.dot(vert.vector) < 0:
                # Segments point opposite directions
                if (horz.start - vert.start).length <= 1e-8:
                    return horz.start
                return horz.end
            # Otherwise they are pointing the same direction
            if (horz.start - vert.end).length < 1e-8:
                return horz.start
            return horz.end
        # If we didn't hit a degenerate case we can treat the segments as infinite lines
        intersect_ratio = (vert.start - horz.start).cross(vert.vector) / denom
        return horz.point_at_ratio(intersect_ratio)


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