added 'split and break bezier at t' extension

extensions/fablabchemnitz/split_and_break_bezier_at_t/split_and_break_bezier_at_t.inx

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<inkscape-extension xmlns="http://www.inkscape.org/namespace/inkscape/extension">
+    <name>Split And Break Bezier At t</name>
+    <id>fablabchemnitz.de.split_and_break_bezier_at_t</id>
+    <param name="target_t" type="float" min="0.0000" max="1.0000" precision="4" appearance="full" gui-text="t">0.5000</param>
+    <label xml:space="preserve">Splits a path at value t=0..1 (t=0.5 means 50%)
+Applies independently for each sub path in selection.</label>
+    <effect>
+        <object-type>path</object-type>
+        <effects-menu>
+            <submenu name="FabLab Chemnitz">
+                <submenu name="Modify existing Path(s)"/>
+            </submenu>
+        </effects-menu>
+    </effect>
+    <script>
+        <command location="inx" interpreter="python">split_and_break_bezier_at_t.py</command>
+    </script>
+</inkscape-extension>

extensions/fablabchemnitz/split_and_break_bezier_at_t/split_and_break_bezier_at_t.py

@@ -0,0 +1,79 @@
+#!/usr/bin/env python3
+
+import copy
+import inkex
+from inkex import bezier, CubicSuperPath, PathElement, Path
+from inkex.bezier import csplength
+
+class SplitAndBreakBezierAtT(inkex.EffectExtension):
+
+    def breakContours(self, element, breakelements = None):
+        ''' this does the same as "CTRL + SHIFT + K" '''
+        if breakelements == None:
+            breakelements = []
+        if element.tag == inkex.addNS('path','svg'):
+            parent = element.getparent()
+            idx = parent.index(element)
+            idSuffix = 0    
+            raw = element.path.to_arrays()
+            subPaths, prev = [], 0
+            for i in range(len(raw)): # Breaks compound paths into simple paths
+                if raw[i][0] == 'M' and i != 0:
+                    subPaths.append(raw[prev:i])
+                    prev = i
+            subPaths.append(raw[prev:])
+            for subpath in subPaths:
+                replacedelement = copy.copy(element)
+                oldId = replacedelement.get('id')
+                replacedelement.set('d', CubicSuperPath(subpath))
+                replacedelement.set('id', oldId + str(idSuffix).zfill(5))
+                parent.insert(idx, replacedelement)
+                idSuffix += 1
+                breakelements.append(replacedelement)
+            parent.remove(element)
+        for child in element.getchildren():
+            self.breakContours(child, breakelements)
+        return breakelements
+
+    def add_arguments(self, pars):
+        pars.add_argument('--target_t', type=float, default=0.5)
+
+    def effect(self):   
+        breakApartElements = None
+        for element in self.svg.selection.filter(PathElement):
+            breakApartElements = self.breakContours(element, breakApartElements)
+        for element in breakApartElements:
+            csp = element.path.to_superpath()
+            slengths, totalLength = csplength(csp)
+            length_at_target_t = self.options.target_t * totalLength
+            new = []
+            lengthSum = 0
+            segOfTOccurence = None   
+            for seg in csp:        
+                new.append([seg[0][:]])      
+                for i in range(1,len(seg)):
+                    segLength = bezier.cspseglength(new[-1][-1], seg[i])
+                    lengthSum += segLength
+                    current_t = lengthSum / totalLength
+                    #insert a new breaking node in case we are at the desired t parameter
+                    if current_t >= self.options.target_t:
+                        if segOfTOccurence is None:
+                            segOfTOccurence = i
+                            t_dist = 1 - ((lengthSum - length_at_target_t) / segLength)
+                            result = bezier.cspbezsplitatlength(new[-1][-1], seg[i], t_dist)
+                            better_result = [[list(el) for el in elements] for elements in result]
+                            new[-1][-1], nxt, seg[i] = better_result
+                            new[-1].append(nxt[:])
+                    new[-1].append(seg[i])                
+            newpath = CubicSuperPath(new).to_path(curves_only=True).to_arrays()
+            #insert the splitting at the occurence (we add "m 0,0") to break the path
+            newpath.insert(segOfTOccurence + 1, ['m', [0, 0]])
+            element.path = Path(newpath)
+            breakApartElements = self.breakContours(element)
+            
+            #print the breaking point coordinate
+            #for step, (x, y) in enumerate(breakApartElements[1].path.end_points):
+            #    self.msg("x={},y={}".format(x, y))
+            #    break
+if __name__ == '__main__':
+    SplitAndBreakBezierAtT().run()