Get basic matching algorithm working

lib/stroke_extractor.js

@@ -1,3 +1,4 @@
+var MAX_BRIDGE_DISTANCE = 64;
 var MIN_CORNER_ANGLE = 0.1*Math.PI;
 var MIN_CORNER_TANGENT_DISTANCE = 4;
 
@@ -21,6 +22,9 @@ var Angle = {
     }
     return result;
   },
+  penalty: function(diff) {
+    return diff*diff*(diff < 0 ? 4 : 1);
+  },
 };
 
 // Helper methods for use with "points", which are just pairs of integers.
@@ -138,19 +142,45 @@ function get_2x_area(path) {
 // Returns a list of critical segments that are arrayed around the corner.
 // Each of these segments will include a d value, an "in" bit, and an "out" bit.
 function get_segments(corners) {
-  var map = {};
+  var result = [[], []];
   for (var i = 0; i < corners.length; i++) {
-    var corner = corners[i];
     for (var j = 0; j < 2; j++) {
-      var key = Point.key(corner.indices[j]);
-      if (!map.hasOwnProperty(key)) {
-        map[key] = {segment: corner.segments[j]};
-      }
+      result[j].push({
+        angle: corners[i].angles[j],
+        point: corners[i].point,
+      });
     }
-    map[Point.key(corner.indices[0])].in = true;
-    map[Point.key(corner.indices[1])].out = true;
   }
-  return _.values(map);
+  return result;
+}
+
+// Takes a list of segments and returns a bipartite match array between them.
+// If array[i] === j, then segments[0][i] is matched with segments[1][j].
+function match_segments(segments) {
+  var matrix = [];
+  for (var i = 0; i < segments[0].length; i++) {
+    matrix.push([]);
+    for (var j = 0; j < segments[0].length; j++) {
+      matrix[i].push(score_segments(segments[0][i], segments[1][j]));
+    }
+  }
+  return (new Hungarian(matrix)).x_match;
+}
+
+// Takes two segments and returns the score that should be assigned to matching
+// the in segment to the out segment. The score will generally be negative.
+function score_segments(ins, out) {
+  var diff = Point.subtract(out.point, ins.point);
+  if (Point.equal(diff, [0, 0])) {
+    return -Angle.penalty(Angle.subtract(out.angle, ins.angle));
+  }
+  var angle = Math.atan2(diff[1], diff[0]);
+  var threshold = Math.pow(MAX_BRIDGE_DISTANCE, 2);
+  var score = 0;
+  score -= Angle.penalty(Angle.subtract(angle, ins.angle));
+  score -= Angle.penalty(Angle.subtract(out.angle, angle));
+  score -= Point.distance2(out.point, ins.point)/threshold;
+  return score;
 }
 
 function Endpoint(paths, index) {
@@ -192,9 +222,12 @@ this.get_glyph_render_data = function(glyph) {
     }
   }
   var corners = endpoints.filter(function(x) { return x.corner; });
+  var segments = get_segments(corners);
+  var matching = match_segments(segments);
   return {
     d: Glyphs.get_svg_path(glyph),
     endpoints: endpoints,
-    segments: get_segments(corners),
+    segments: segments,
+    matching: matching,
   };
 }