77 lines
3.6 KiB
Python
77 lines
3.6 KiB
Python
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#!/usr/bin/env python3
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"""
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Derived from the "envelope" extension by Aaron Spike, aaron@ekips.org
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By Apex 2011
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New version Jens Kober 2017, 2020
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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"""
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import inkex
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from inkex.localization import inkex_gettext as _
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class Mirror(inkex.EffectExtension):
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def effect(self):
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if len(self.options.ids) < 2:
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raise inkex.AbortExtension(_("This extension requires two selected objects. \nThe second must be a path, exactly two nodes long."))
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#trafo is selected second
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obj = self.svg.selected[self.options.ids[0]]
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trafo = self.svg.selected[self.options.ids[1]]
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if isinstance(trafo, inkex.PathElement):
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#distil trafo into two node points
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trafoPath = trafo.path.transform(trafo.composed_transform()).to_superpath()
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if len(trafoPath[0]) != 2:
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raise inkex.AbortExtension(_("The second selected object must be exactly two nodes long."))
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# origin of mirror line
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ox = trafoPath[0][0][1][0]
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oy = trafoPath[0][0][1][1]
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# vector along mirror line
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vx = trafoPath[0][1][1][0] - ox
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vy = trafoPath[0][1][1][1] - oy
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# the transformation first translates the origin of the mirror line to [0 0], then rotates the mirror line onto the x-axis,
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# reflects everything over the x-axis, undoes the rotation, and finally undoes the translation
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# alpha = atan2(vy, vx);
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# [1 0 ox] [cos(alpha) -sin(alpha) 0] [1 0 0] [cos(-alpha) -sin(-alpha) 0] [1 0 -ox]
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# Transformation = [0 1 oy]*[sin(alpha) cos(alpha) 0]*[0 -1 0]*[sin(-alpha) cos(-alpha) 0]*[0 1 -oy]
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# [0 0 1] [ 0 0 1] [0 0 1] [ 0 0 1] [0 0 1]
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# after some simplifications (or using your favorite symbolic math software):
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# [(vx^2-vy^2)/(vx^2+vy^2) (2 vx vy)/(vx^2+vy^2) (2 vy (ox vy-oy vx))/(vx^2+vy^2)]
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# Transformation = [ (2 vx vy)/(vx^2+vy^2) -(vx^2-vy^2)/(vx^2+vy^2) -(2 vx (ox vy-oy vx))/(vx^2+vy^2)]
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# [ 0 0 1]
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denom = vx**2 + vy**2
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a00 = (vx**2 - vy**2) / denom
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a01 = (2 * vx * vy) / denom
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a02 = 2 * (ox * vy - oy * vx) / denom
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mat=[[a00, a01, vy * a02], [a01, -a00, -vx * a02]]
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obj.transform = inkex.Transform(mat) @ obj.transform
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else:
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if isinstance(trafo, inkex.Group):
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raise inkex.AbortExtension(_("The second selected object is a group, not a path.\nTry using the procedure Object->Ungroup."))
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else:
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raise inkex.AbortExtension(_("The second selected object is not a path.\nTry using the procedure Path->Object to Path."))
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if __name__ == '__main__':
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Mirror().run()
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