added Label Color extension

extensions/fablabchemnitz_label_color.inx

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<inkscape-extension xmlns="http://www.inkscape.org/namespace/inkscape/extension">
+    <name>Label Feature With Fill Color</_ame>
+    <id>fablabchemnitz.de.label_color</id>
+    <effect>
+        <object-type>all</object-type>
+        <effects-menu>
+            <submenu name="FabLab Chemnitz">
+                <submenu name="Various"/>
+            </submenu>
+        </effects-menu>
+    </effect>
+    <script>
+        <command reldir="extensions" interpreter="python">fablabchemnitz_label_color.py</command>
+    </script>
+</inkscape-extension>

extensions/fablabchemnitz_label_color.py

@@ -0,0 +1,144 @@
+#!/usr/bin/env python3
+
+
+"""
+A inkscape plugin to label features with their fill colour
+
+
+Copyright (C) 2019 Christoph Fink
+
+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.paths import CubicSuperPath, Path
+from lxml import etree
+
+class LabelColour(inkex.Effect):
+    def __init__(self):
+        inkex.Effect.__init__(self)
+
+    def effect(self):
+        if len(self.svg.selected) > 0:
+            for id, node in self.svg.selected.items():
+                self.labelFeature(node)
+
+    def labelFeature(self, node):
+        style = node.get('style')
+        if style:
+            nodeStyle = dict(inkex.Style.parse_str(node.attrib["style"]))
+            nodeColour, labelColour = self.getNodeAndLabelColours(nodeStyle["fill"])
+            nodeX, nodeY, nodeWidth, nodeHeight = self.getNodeDimensions(node)
+            parent = node.getparent()
+            label = etree.SubElement(
+                parent,
+                inkex.addNS("text", "svg"),
+                {
+                    "font-size": str(nodeHeight/4),
+                    "x": str(nodeX + (nodeWidth/2)),
+                    "y": str(nodeY + (nodeHeight/2)),
+                    "dy": "0.5em",
+                    "style": str(inkex.Style({
+                        "fill": labelColour,
+                        "stroke": "none",
+                        "text-anchor": "middle"
+                    }))
+                }
+            )
+            labelTextSpan = etree.SubElement(
+                label,
+                inkex.addNS("tspan", "svg"),
+                {}
+            )
+            labelTextSpan.text = nodeColour
+
+
+    def getNodeAndLabelColours(self, nodeStyleFill):
+        if nodeStyleFill[:5] == "url(#":
+            nodeFill = self.svg.getElementById(nodeStyleFill[5:-1])
+            if "Gradient" in nodeFill.tag:
+                nodeColour, labelColour = self.getNodeAndLabelColourForGradient(nodeFill)
+            else:
+                nodeColour = ""
+                labelColour = ""
+
+        else:
+            nodeColour = nodeStyleFill
+            labelColour = self.getLabelColour(nodeColour)
+
+        return (nodeColour, labelColour)
+
+    def getNodeAndLabelColourForGradient(self, gradientNode):
+        stops = self.getGradientStops(gradientNode)
+
+        nodeColours = []
+
+        for stop in stops:
+            offset = float(stop[0])
+            colour = stop[1]
+            nodeColours.append("{colour:s}{offset:s}".format(
+                colour=colour,
+                offset="" if offset in (0, 1) else " ({:0.2f})".format(offset)
+            ))
+        nodeColour = u" ↔ ".join(nodeColours)
+
+        avgNodeColour = [sum([inkex.Color(stop[1]).to_rgb()[c] for stop in stops]) / len(stops) for c in range(3)]
+
+        labelColour = str(inkex.Color(avgNodeColour))
+
+        return (nodeColour, labelColour)
+
+    def getGradientStops(self, gradientNode):
+        while "{http://www.w3.org/1999/xlink}href" in gradientNode.attrib:
+            gradientNode = self.svg.getElementById(gradientNode.attrib["{http://www.w3.org/1999/xlink}href"][1:])  # noqa:E129
+
+        stops = []
+
+        for child in gradientNode:
+            if "stop" in child.tag:
+                stopStyle = dict(inkex.Style.parse_str(child.attrib["style"]))
+                stops.append((child.attrib["offset"], stopStyle["stop-color"]))
+
+        # if only opacity differs (colour == same), return one stop only:
+        if len(set([s[1] for s in stops])) == 1:
+            stops = [(0, stops[0][1])]
+
+        return stops
+
+    def getLabelColour(self, nodeColour):
+        labelColour = "#000000"
+
+        try:
+            nodeColour = inkex.Color(nodeColour).to_rgb()
+            if sum(nodeColour) / len(nodeColour) < 128:
+                labelColour = "#ffffff"
+        except (
+            TypeError,
+            ZeroDivisionError  # if parseColor returns ""
+        ):
+            pass
+
+        return labelColour
+
+    def getNodeDimensions(self, node):
+        bbox = node.bounding_box()
+        nodeX = bbox.left
+        nodeY = bbox.top
+        nodeWidth = bbox.right - bbox.left
+        nodeHeight = bbox.bottom - bbox.top
+            
+        return nodeX, nodeY, nodeWidth, nodeHeight
+
+LabelColour().run()