improved README curve offsetting example

README.ipynb

@@ -86,7 +86,7 @@
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+   "execution_count": 16,
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@@ -97,7 +97,7 @@
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@@ -147,7 +147,7 @@
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@@ -224,7 +224,7 @@
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@@ -265,7 +265,7 @@
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@@ -300,7 +300,7 @@
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@@ -363,7 +363,7 @@
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@@ -411,7 +411,7 @@
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@@ -466,7 +466,7 @@
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@@ -509,7 +509,7 @@
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+   "execution_count": 25,
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@@ -551,7 +551,7 @@
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@@ -606,7 +606,7 @@
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-   "execution_count": 32,
+   "execution_count": 27,
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    },
@@ -635,65 +635,58 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "### An Advanced Application:  Offsetting Bezier Curves\n",
-    "Here we'll find the [offset curve](https://en.wikipedia.org/wiki/Parallel_curve) for a few Bezier cubics."
+    "### An Advanced Application:  Offsetting Paths\n",
+    "Here we'll find the [offset curve](https://en.wikipedia.org/wiki/Parallel_curve) for a few paths."
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 33,
+   "execution_count": 28,
    "metadata": {
-    "collapsed": true
+    "collapsed": false
    },
    "outputs": [],
    "source": [
-    "def display_offset_curve(bezpath, offset_distance, steps=1000,\n",
-    "                         stripe_width=3, stripe_colors='ygb',\n",
-    "                         name='offsetcurves.svg', show_normal_line=True):\n",
-    "    \"\"\"Takes in a path of bezier curves, `bezpath`, and a distance,\n",
-    "    `offset_distance`, and displays the 'parallel' offset curve by placing a\n",
-    "    dot at a distance of `offset_distance` away at each step.\"\"\"\n",
+    "from svgpathtools import parse_path, Line, Path, wsvg\n",
+    "def offset_curve(path, offset_distance, steps=1000):\n",
+    "    \"\"\"Takes in a Path object, `path`, and a distance,\n",
+    "    `offset_distance`, and outputs an piecewise-linear approximation \n",
+    "    of the 'parallel' offset curve.\"\"\"\n",
     "    nls = []\n",
-    "    nodes = []\n",
-    "    line_colors = ''\n",
-    "    node_colors = ''\n",
-    "\n",
-    "    for bez in bezpath:\n",
+    "    for seg in path:\n",
     "        ct = 1\n",
     "        for k in range(steps):\n",
     "            t = k / steps\n",
-    "            nl = Line(bez.point(t),\n",
-    "                      bez.point(t) + offset_distance * bez.normal(t))\n",
+    "            offset_vector = offset_distance * seg.normal(t)\n",
+    "            nl = Line(seg.point(t), seg.point(t) + offset_vector)\n",
     "            nls.append(nl)\n",
-    "            line_colors += stripe_colors[ct % 3]\n",
-    "            if not (k % stripe_width):\n",
-    "                ct += 1\n",
-    "            nodes.append(bez.point(t))\n",
-    "            nodes.append(nl.end)\n",
-    "            node_colors += 'kr'\n",
-    "    # nls.reverse()\n",
-    "    if show_normal_line:\n",
-    "        wsvg([bezpath] + nls, 'k' + line_colors,\n",
-    "             nodes=nodes, node_colors=node_colors,\n",
-    "             filename=name)\n",
-    "    else:\n",
-    "        wsvg(bezpath, 'k',\n",
-    "             nodes=nodes, node_colors=node_colors,\n",
-    "             filename=name)\n",
+    "    connect_the_dots = [Line(nls[k].end, nls[k+1].end) for k in range(len(nls)-1)]\n",
+    "    if path.isclosed():\n",
+    "        connect_the_dots.append(Line(nls[-1].end, nls[0].end))\n",
+    "    offset_path = Path(*connect_the_dots)\n",
+    "    return offset_path\n",
     "\n",
-    "bez1 = parse_path(\"m 288,600 c -52,-28 -42,-61 0,-97 \")[0]\n",
-    "bez2 = parse_path(\"M 151,395 C 407,485 726.17662,160 634,339\")[0]\n",
-    "bez3 = parse_path(\"m 117,695 c 237,-7 -103,-146 457,0\")[0]\n",
-    "path = Path(bez1, bez2.translated(300), bez3.translated(500+400j))\n",
+    "# Examples:\n",
+    "path1 = parse_path(\"m 288,600 c -52,-28 -42,-61 0,-97 \")\n",
+    "path2 = parse_path(\"M 151,395 C 407,485 726.17662,160 634,339\").translated(300)\n",
+    "path3 = parse_path(\"m 117,695 c 237,-7 -103,-146 457,0\").translated(500+400j)\n",
+    "paths = [path1, path2, path3]\n",
     "\n",
-    "display_offset_curve(path, 500)"
+    "offset_distances = [10*k for k in range(1,51)]\n",
+    "offset_paths = []\n",
+    "for path in paths:\n",
+    "    for distances in offset_distances:\n",
+    "        offset_paths.append(offset_curve(path, distances))\n",
+    "\n",
+    "# Note: This will take a few moments\n",
+    "wsvg(paths + offset_paths, 'g'*len(paths) + 'r'*len(offset_paths), filename='offset_curves.svg')"
    ]
   },
   {
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "![offsetcurves.svg](offsetcurves.svg)"
+    "![offset_curves.svg](offset_curves.svg)"
    ]
   },
   {

README.rst

@@ -453,7 +453,7 @@ Translations (shifts), reversing orientation, and normal vectors
          'bgpkgp', nodes=[b.point(t), br.point(t)], filename='vectorframes.svg', 
          text=["b's tangent", "br's tangent"], text_path=[tangent_line, tangent_line_r])
 
-.. figure:: https://cdn.rawgit.com/mathandy/svgpathtools/master/test.svg
+.. figure:: https://cdn.rawgit.com/mathandy/svgpathtools/master/vectorframes.svg
    :alt: vectorframes.svg
 
    vectorframes.svg
@@ -554,60 +554,52 @@ Intersections between Bezier curves
 
    output\_intersections.svg
 
-An Advanced Application: Offsetting Bezier Curves
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+An Advanced Application: Offsetting Paths
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Here we'll find the `offset
-curve <https://en.wikipedia.org/wiki/Parallel_curve>`__ for a few Bezier
-cubics.
+curve <https://en.wikipedia.org/wiki/Parallel_curve>`__ for a few paths.
 
 .. code:: python
 
-    def display_offset_curve(bezpath, offset_distance, steps=1000,
-                             stripe_width=3, stripe_colors='ygb',
-                             name='offsetcurves.svg', show_normal_line=True):
-        """Takes in a path of bezier curves, `bezpath`, and a distance,
-        `offset_distance`, and displays the 'parallel' offset curve by placing a
-        dot at a distance of `offset_distance` away at each step."""
+    from svgpathtools import parse_path, Line, Path, wsvg
+    def offset_curve(path, offset_distance, steps=1000):
+        """Takes in a Path object, `path`, and a distance,
+        `offset_distance`, and outputs an piecewise-linear approximation 
+        of the 'parallel' offset curve."""
         nls = []
-        nodes = []
-        line_colors = ''
-        node_colors = ''
-    
-        for bez in bezpath:
+        for seg in path:
             ct = 1
             for k in range(steps):
                 t = k / steps
-                nl = Line(bez.point(t),
-                          bez.point(t) + offset_distance * bez.normal(t))
+                offset_vector = offset_distance * seg.normal(t)
+                nl = Line(seg.point(t), seg.point(t) + offset_vector)
                 nls.append(nl)
-                line_colors += stripe_colors[ct % 3]
-                if not (k % stripe_width):
-                    ct += 1
-                nodes.append(bez.point(t))
-                nodes.append(nl.end)
-                node_colors += 'kr'
-        # nls.reverse()
-        if show_normal_line:
-            wsvg([bezpath] + nls, 'k' + line_colors,
-                 nodes=nodes, node_colors=node_colors,
-                 filename=name)
-        else:
-            wsvg(bezpath, 'k',
-                 nodes=nodes, node_colors=node_colors,
-                 filename=name)
+        connect_the_dots = [Line(nls[k].end, nls[k+1].end) for k in range(len(nls)-1)]
+        if path.isclosed():
+            connect_the_dots.append(Line(nls[-1].end, nls[0].end))
+        offset_path = Path(*connect_the_dots)
+        return offset_path
     
-    bez1 = parse_path("m 288,600 c -52,-28 -42,-61 0,-97 ")[0]
-    bez2 = parse_path("M 151,395 C 407,485 726.17662,160 634,339")[0]
-    bez3 = parse_path("m 117,695 c 237,-7 -103,-146 457,0")[0]
-    path = Path(bez1, bez2.translated(300), bez3.translated(500+400j))
+    # Examples:
+    path1 = parse_path("m 288,600 c -52,-28 -42,-61 0,-97 ")
+    path2 = parse_path("M 151,395 C 407,485 726.17662,160 634,339").translated(300)
+    path3 = parse_path("m 117,695 c 237,-7 -103,-146 457,0").translated(500+400j)
+    paths = [path1, path2, path3]
     
-    display_offset_curve(path, 500)
+    offset_distances = [10*k for k in range(1,51)]
+    offset_paths = []
+    for path in paths:
+        for distances in offset_distances:
+            offset_paths.append(offset_curve(path, distances))
+    
+    # Note: This will take a few moments
+    wsvg(paths + offset_paths, 'g'*len(paths) + 'r'*len(offset_paths), filename='offset_curves.svg')
 
-.. figure:: https://cdn.rawgit.com/mathandy/svgpathtools/master/offsetcurves.svg
-   :alt: offsetcurves.svg
+.. figure:: https://cdn.rawgit.com/mathandy/svgpathtools/master/offset_curves.svg
+   :alt: offset\_curves.svg
 
-   offsetcurves.svg
+   offset\_curves.svg
 
 Compatibility Notes for users of svg.path (v2.0)
 ------------------------------------------------