Update to trunk

(bzr r13090.1.45)

2 files changed, 72 insertions, 21 deletions

diff --git a/share/extensions/measure.inx b/share/extensions/measure.inx
index cfbc3fce7..8fae020e0 100644
--- a/share/extensions/measure.inx
+++ b/share/extensions/measure.inx
@@ -9,6 +9,7 @@
 			<param name="type" type="enum" _gui-text="Measurement Type: ">
 				<_item value="length">Length</_item>
 				<_item msgctxt="measure extension" value="area">Area</_item>
+				<_item msgctxt="measure extension" value="cofm">Center of Mass</_item>
 			</param>
 			<param name="format" type="enum" _gui-text="Text Orientation: ">
 				<_item msgctxt="measure extension" value="textonpath">Text On Path</_item>
@@ -32,9 +33,9 @@
 			</param>
 		</page>
 		<page name="desc" _gui-text="Help">
-			<_param name="measurehelp" type="description" xml:space="preserve">This effect measures the length, or area, of the selected paths and adds it as a text object with the selected units.
-            
-  * Display format can be either Text-On-Path, or stand-alone text at a specified angle.
+			<_param name="measurehelp" type="description" xml:space="preserve">This effect measures the length, area, or center-of-mass of the selected paths. Length and area are added as a text object with the selected units. Center-of-mass is shown as a cross symbol.
+
+  * Text display format can be either Text-On-Path, or stand-alone text at a specified angle.
   * The number of significant digits can be controlled by the Precision field.
   * The Offset field controls the distance from the text to the path.
   * The Scale factor can be used to make measurements in scaled drawings. For example, if 1 cm in the drawing equals 2.5 m in the real world, Scale must be set to 250.
diff --git a/share/extensions/measure.py b/share/extensions/measure.py
index ca471816f..5c709594f 100755
--- a/share/extensions/measure.py
+++ b/share/extensions/measure.py
@@ -1,8 +1,9 @@
 #!/usr/bin/env python 
 '''
 This extension module can measure arbitrary path and object length
-It adds a text to the selected path containing the length in a
-given unit.
+It adds text to the selected path containing the length in a given unit.
+Area and Center of Mass calculated using Green's Theorem:
+http://mathworld.wolfram.com/GreensTheorem.html
 
 Copyright (C) 2010 Alvin Penner
 Copyright (C) 2006 Georg Wiora
@@ -30,10 +31,31 @@ TODO:
     2. check direction >90 or <-90 Degrees
     3. rotate by 180 degrees around text center
 '''
-import inkex, simplestyle, simplepath, simpletransform, sys, cubicsuperpath, bezmisc, locale
-# Set current system locale
+# standard library
+import locale
+# local library
+import inkex
+import simplestyle
+import simpletransform
+import cubicsuperpath
+import bezmisc
+
+inkex.localize()
 locale.setlocale(locale.LC_ALL, '')
 
+# third party
+try:
+    import numpy
+except:
+    inkex.errormsg(_("Failed to import the numpy modules. These modules are required by this extension. Please install them and try again.  On a Debian-like system this can be done with the command, sudo apt-get install python-numpy."))
+    exit()
+
+mat_area   = numpy.matrix([[  0,  2,  1, -3],[ -2,  0,  1,  1],[ -1, -1,  0,  2],[  3, -1, -2,  0]])
+mat_cofm_0 = numpy.matrix([[  0, 35, 10,-45],[-35,  0, 12, 23],[-10,-12,  0, 22],[ 45,-23,-22,  0]])
+mat_cofm_1 = numpy.matrix([[  0, 15,  3,-18],[-15,  0,  9,  6],[ -3, -9,  0, 12],[ 18, -6,-12,  0]])
+mat_cofm_2 = numpy.matrix([[  0, 12,  6,-18],[-12,  0,  9,  3],[ -6, -9,  0, 15],[ 18, -3,-15,  0]])
+mat_cofm_3 = numpy.matrix([[  0, 22, 23,-45],[-22,  0, 12, 10],[-23,-12,  0, 35],[ 45,-10,-35,  0]])
+
 def numsegs(csp):
     return sum([len(p)-1 for p in csp])
 def interpcoord(v1,v2,p):
@@ -69,20 +91,37 @@ def csplength(csp):
         for i in xrange(1,len(sp)):
             l = cspseglength(sp[i-1],sp[i])
             lengths[-1].append(l)
-            total += l            
+            total += l
     return lengths, total
 def csparea(csp):
     area = 0.0
     for sp in csp:
+        if len(sp) < 2: continue
         for i in range(len(sp)):            # calculate polygon area
             area += 0.5*sp[i-1][1][0]*(sp[i][1][1] - sp[i-2][1][1])
         for i in range(1, len(sp)):         # add contribution from cubic Bezier
-            bezarea  = ( 0.0*sp[i-1][1][1] + 2.0*sp[i-1][2][1] + 1.0*sp[i][0][1] - 3.0*sp[i][1][1])*sp[i-1][1][0]
-            bezarea += (-2.0*sp[i-1][1][1] + 0.0*sp[i-1][2][1] + 1.0*sp[i][0][1] + 1.0*sp[i][1][1])*sp[i-1][2][0]
-            bezarea += (-1.0*sp[i-1][1][1] - 1.0*sp[i-1][2][1] + 0.0*sp[i][0][1] + 2.0*sp[i][1][1])*sp[i][0][0]
-            bezarea += ( 3.0*sp[i-1][1][1] - 1.0*sp[i-1][2][1] - 2.0*sp[i][0][1] + 0.0*sp[i][1][1])*sp[i][1][0]
-            area += 0.15*bezarea
-    return abs(area)
+            vec_x = numpy.matrix([sp[i-1][1][0], sp[i-1][2][0], sp[i][0][0], sp[i][1][0]])
+            vec_y = numpy.matrix([sp[i-1][1][1], sp[i-1][2][1], sp[i][0][1], sp[i][1][1]])
+            area += 0.15*(vec_x*mat_area*vec_y.T)[0,0]
+    return -area                            # require positive area for CCW
+def cspcofm(csp):
+    area = csparea(csp)
+    xc = 0.0
+    yc = 0.0
+    if abs(area) < 1.e-8:
+        inkex.errormsg(_("Area is zero, cannot calculate Center of Mass"))
+        return 0, 0
+    for sp in csp:
+        for i in range(len(sp)):            # calculate polygon moment
+            xc += sp[i-1][1][1]*(sp[i-2][1][0] - sp[i][1][0])*(sp[i-2][1][0] + sp[i-1][1][0] + sp[i][1][0])/6
+            yc += sp[i-1][1][0]*(sp[i][1][1] - sp[i-2][1][1])*(sp[i-2][1][1] + sp[i-1][1][1] + sp[i][1][1])/6
+        for i in range(1, len(sp)):         # add contribution from cubic Bezier
+            vec_x = numpy.matrix([sp[i-1][1][0], sp[i-1][2][0], sp[i][0][0], sp[i][1][0]])
+            vec_y = numpy.matrix([sp[i-1][1][1], sp[i-1][2][1], sp[i][0][1], sp[i][1][1]])
+            vec_t = numpy.matrix([(vec_x*mat_cofm_0*vec_y.T)[0,0], (vec_x*mat_cofm_1*vec_y.T)[0,0], (vec_x*mat_cofm_2*vec_y.T)[0,0], (vec_x*mat_cofm_3*vec_y.T)[0,0]])
+            xc += (vec_x*vec_t.T)[0,0]/280
+            yc += (vec_y*vec_t.T)[0,0]/280
+    return -xc/area, -yc/area
 def appendSuperScript(node, text):
     super = inkex.etree.SubElement(node, inkex.addNS('tspan', 'svg'), {'style': 'font-size:65%;baseline-shift:super'})
     super.text = text
@@ -133,12 +172,13 @@ class Length(inkex.Effect):
         self.OptionParser.add_option("--measurehelp",
                         action="store", type="string", 
                         dest="measurehelp", default="",
-                        help="dummy") 
-                        
+                        help="dummy")
+
     def effect(self):
         # get number of digits
         prec = int(self.options.precision)
-        self.options.offset *= self.unittouu('1px')
+        scale = self.unittouu('1px')    # convert to document units
+        self.options.offset *= scale
         factor = 1.0
         doc = self.document.getroot()
         if doc.get('viewBox'):
@@ -150,16 +190,21 @@ class Length(inkex.Effect):
         # loop over all selected paths
         for id, node in self.selected.iteritems():
             if node.tag == inkex.addNS('path','svg'):
-                self.group = inkex.etree.SubElement(node.getparent(),inkex.addNS('text','svg'))
-                a =[]
                 mat = simpletransform.composeParents(node, [[1.0, 0.0, 0.0], [0.0, 1.0, 0.0]])
                 p = cubicsuperpath.parsePath(node.get('d'))
                 simpletransform.applyTransformToPath(mat, p)
-                factor *= self.unittouu('1px')/self.unittouu('1'+self.options.unit)
+                factor *= scale/self.unittouu('1'+self.options.unit)
                 if self.options.type == "length":
                     slengths, stotal = csplength(p)
-                else:
+                    self.group = inkex.etree.SubElement(node.getparent(),inkex.addNS('text','svg'))
+                elif self.options.type == "area":
                     stotal = csparea(p)*factor*self.options.scale
+                    self.group = inkex.etree.SubElement(node.getparent(),inkex.addNS('text','svg'))
+                else:
+                    xc, yc = cspcofm(p)
+                    self.group = inkex.etree.SubElement(node.getparent(),inkex.addNS('path','svg'))
+                    self.addCross(self.group, xc, yc, scale)
+                    continue
                 # Format the length as string
                 lenstr = locale.format("%(len)25."+str(prec)+"f",{'len':round(stotal*factor*self.options.scale,prec)}).strip()
                 if self.options.format == 'textonpath':
@@ -173,6 +218,11 @@ class Length(inkex.Effect):
                     else:
                         self.addTextWithTspan(self.group, p[0][0][1][0], p[0][0][1][1], lenstr+' '+self.options.unit+'^2', id, 'start', -int(self.options.angle), -self.options.offset + self.options.fontsize/2)
 
+    def addCross(self, node, x, y, scale):
+        l = 3*scale         # 3 pixels in document units
+        node.set('d', 'm %s,%s %s,0 m %s,%s 0,%s' % (str(x-l), str(y), str(2*l), str(-l), str(-l), str(2*l)))
+        node.set('style', 'stroke:#000000;stroke-width:%s' % str(0.5*scale))
+
     def addTextOnPath(self, node, x, y, text, id, anchor, startOffset, dy = 0):
                 new = inkex.etree.SubElement(node,inkex.addNS('textPath','svg'))
                 s = {'text-align': 'center', 'vertical-align': 'bottom',