Added Affine Spirals

extensions/fablabchemnitz_affine_spirals.inx

@@ -0,0 +1,26 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<inkscape-extension xmlns="http://www.inkscape.org/namespace/inkscape/extension">
+   <_name>Affine Spirals</_name>
+   <id>fablabchemnitz.de.affine_torus</id>
+   <param name="active-tab" type="notebook">
+      <page name="title" _gui-text="Settings">
+         <param name="num_lines" type="int" min="1" max="6" _gui-text="Depth">3</param>
+         <param name="num_petals" type="int" min="2" max="8" _gui-text="petals">2</param>
+         <param name="shrink_ratio" type="float" min="0.1" max="0.9" precision="2" _gui-text="shrink factor">0.8</param>
+         <_param name="help" type="description" xml:space="preserve">------------------------------</_param>
+         <!--<param name="mk_full" type="boolean" _gui-text="Full Koch">true</param>
+			<param name="mk_filled" type="boolean" _gui-text="Filled">false</param>-->
+      </page>
+   </param>
+   <effect>
+      <object-type>all</object-type>
+      <effects-menu>
+         <submenu _name="FabLab Chemnitz">
+			<submenu _name="Shape/Pattern from Generator" />
+         </submenu>
+      </effects-menu>
+   </effect>
+   <script>
+      <command reldir="extensions" interpreter="python">fablabchemnitz_affine_spirals.py</command>
+   </script>
+</inkscape-extension>

extensions/fablabchemnitz_affine_spirals.py

@@ -0,0 +1,100 @@
+#!/usr/bin/env python3
+
+import inkex
+from lxml import etree
+from math import cos, sin, pi, exp
+__version__ = '0.1'
+inkex.localization.localize
+
+def line(npts=40, x0=0, y0=0, delta=.5, sgn=1):
+    #returns a list of points on a line (y = +/- x + c) starting at x0,y0
+    return [ (x0 + delta*t, y0 + sgn*delta*t) for t in range(npts)]
+    
+def ff(v, ww=.25, ds=.4): 
+    #covering map from R^2 ro punctured plane
+    x,y = v
+    r,u = exp(-ds*x), cos(pi*ww*y) + 1J*sin(pi*ww*y)
+    return r*u
+    
+def mk_plugs(pts):
+	#returns a list of complex representing a plug type segment
+    segs = [fit_plug(end_pts) for end_pts in zip(pts,pts[1:]) ]
+    tmp  = []
+    for seg in segs:
+        tmp.extend(seg) 
+    return tmp
+	
+def fit_plug(ss):
+    a,b = ss
+    rot = complex(b-a)
+    pts = [0,.45,.4 + .15*1J, .6 + .15*1J, .55, 1]
+    return [rot*z + a for z in pts]
+
+def pts2curve(cplxs):
+    '''makes a polyline path element from a list of complex
+    '''
+    def cplx2pt(z):
+        return (z.real,z.imag)
+    
+    scale = 200
+    data = [cplx2pt( scale*z ) for z in cplxs ] 
+    pth = [ '%.2f, %.2f '%z for z in data]
+    return 'M '+ ''.join(pth) 
+        
+class AffineTorus(inkex.Effect): # choose a better name
+    
+    def __init__(self):
+        inkex.Effect.__init__(self)
+        self.arg_parser.add_argument("--num_lines", type=int, default=3)    
+        self.arg_parser.add_argument("--num_petals", type=int, default=3)   
+        self.arg_parser.add_argument("--shrink_ratio", type=float, default=3)
+        #self.arg_parser.add_argument("--mk_filled", type=inkex.Boolean, default=False)
+        self.arg_parser.add_argument("--mk_full", type=inkex.Boolean, default=False)
+        self.arg_parser.add_argument("--active-tab", default='title')
+             
+    def calc_unit_factor(self):
+        unit_factor = self.svg.unittouu(str(1.0) + self.options.units)
+        return unit_factor
+
+    def effect(self):
+        path_stroke = '#DD0000' # take color from tab3
+        path_fill   = 'none'     # no fill - just a line
+        path_stroke_width  = 1. # can also be in form '0.6mm'
+        page_id = self.options.active_tab # sometimes wrong the very first time
+        
+        styles = [ {'stroke':  path_stroke , 'fill': 'none', 'stroke-width': path_stroke_width},
+                   {'stroke': 'none',  'fill': '#FFFF00', 'stroke-width': 0}]
+        
+        styles = [str(inkex.Style(x)) for x in styles]
+
+        # This finds center of current view in inkscape
+        t = 'translate(%s,%s)' % (self.svg.namedview.center[0], self.svg.namedview.center[1])
+        
+        # Make a nice useful name
+        g_attribs = {inkex.addNS('label','inkscape'): 'koch',
+                     inkex.addNS('transform-center-x','inkscape'): str(0),
+                     inkex.addNS('transform-center-y','inkscape'): str(0),
+                     'transform': t,
+                     'style' : styles[1],
+                     'info':'N: '+str(self.options.num_lines) }
+        topgroup = etree.SubElement(self.svg.get_current_layer(), 'g', g_attribs)
+
+        NN = 2*self.options.num_lines
+        NP = self.options.num_petals
+        SF = 2*self.options.shrink_ratio
+        
+        payload = []
+        for y in range(-NP,NP):    
+            mpts = [ff(z,ww=1./NP, ds=SF) for z in line(npts=NN, y0=y)]
+            payload.append(mk_plugs(mpts))
+            mpts = [ff(z,ww=1./NP, ds=SF) for z in line(npts=NN, y0=y,sgn=-1 )]
+            payload.append(mk_plugs(mpts))
+        
+        payload = [pts2curve(cc) for cc in payload]
+        payload = ' '.join(payload)
+            
+        curve_attribs = { 'style': styles[0], 'd': payload}
+        etree.SubElement(topgroup, inkex.addNS('path','svg'), curve_attribs)
+
+if __name__ == '__main__':
+    AffineTorus().run()