Add d3.geo.simplify.

Assumes that the third dimension (z) of each coordinate represents the importance of that coordinate, and implements a filter stream that skips coordinates that fail to meet the minimum importance threshold.
snoble · Aug 15, 2013 · 508ae65 · 508ae65
1 parent 36e5526
commit 508ae65
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Showing 7 changed files with 97 additions and 82 deletions.
diff --git a/d3.js b/d3.js
@@ -2249,12 +2249,11 @@ d3 = function() {
       listener.sphere();
     },
     Point: function(object, listener) {
-      var coordinate = object.coordinates;
-      listener.point(coordinate[0], coordinate[1]);
+      listener.point.apply(listener, object.coordinates);
     },
     MultiPoint: function(object, listener) {
-      var coordinates = object.coordinates, i = -1, n = coordinates.length, coordinate;
-      while (++i < n) coordinate = coordinates[i], listener.point(coordinate[0], coordinate[1]);
+      var coordinates = object.coordinates, i = -1, n = coordinates.length;
+      while (++i < n) listener.point.apply(listener, coordinates[i]);
     },
     LineString: function(object, listener) {
       d3_geo_streamLine(object.coordinates, listener, 0);
@@ -2276,9 +2275,9 @@ d3 = function() {
     }
   };
   function d3_geo_streamLine(coordinates, listener, closed) {
-    var i = -1, n = coordinates.length - closed, coordinate;
+    var i = -1, n = coordinates.length - closed;
     listener.lineStart();
-    while (++i < n) coordinate = coordinates[i], listener.point(coordinate[0], coordinate[1]);
+    while (++i < n) listener.point.apply(listener, coordinates[i]);
     listener.lineEnd();
   }
   function d3_geo_streamPolygon(coordinates, listener) {
@@ -2287,6 +2286,26 @@ d3 = function() {
     while (++i < n) d3_geo_streamLine(coordinates[i], listener, 1);
     listener.polygonEnd();
   }
+  function d3_geo_streamTransform(stream, point) {
+    return {
+      point: point,
+      sphere: function() {
+        stream.sphere();
+      },
+      lineStart: function() {
+        stream.lineStart();
+      },
+      lineEnd: function() {
+        stream.lineEnd();
+      },
+      polygonStart: function() {
+        stream.polygonStart();
+      },
+      polygonEnd: function() {
+        stream.polygonEnd();
+      }
+    };
+  }
   d3.geo.area = function(object) {
     d3_geo_areaSum = 0;
     d3.geo.stream(object, d3_geo_area);
@@ -3556,31 +3575,13 @@ d3 = function() {
     return path.projection(d3.geo.albersUsa()).context(null);
   };
   function d3_geo_pathProjectStream(project) {
-    var resample = d3_geo_resample(function(λ, φ) {
-      return project([ λ * d3_degrees, φ * d3_degrees ]);
+    var resample = d3_geo_resample(function(x, y) {
+      return project([ x * d3_degrees, y * d3_degrees ]);
     });
     return function(stream) {
-      stream = resample(stream);
-      return {
-        point: function(λ, φ) {
-          stream.point(λ * d3_radians, φ * d3_radians);
-        },
-        sphere: function() {
-          stream.sphere();
-        },
-        lineStart: function() {
-          stream.lineStart();
-        },
-        lineEnd: function() {
-          stream.lineEnd();
-        },
-        polygonStart: function() {
-          stream.polygonStart();
-        },
-        polygonEnd: function() {
-          stream.polygonEnd();
-        }
-      };
+      return d3_geo_streamTransform(stream = resample(stream), function(x, y) {
+        stream.point(x * d3_radians, y * d3_radians);
+      });
     };
   }
   d3.geo.projection = d3_geo_projection;
@@ -3663,27 +3664,10 @@ d3 = function() {
     };
   }
   function d3_geo_projectionRadiansRotate(rotate, stream) {
-    return {
-      point: function(x, y) {
-        y = rotate(x * d3_radians, y * d3_radians), x = y[0];
-        stream.point(x > π ? x - 2 * π : x < -π ? x + 2 * π : x, y[1]);
-      },
-      sphere: function() {
-        stream.sphere();
-      },
-      lineStart: function() {
-        stream.lineStart();
-      },
-      lineEnd: function() {
-        stream.lineEnd();
-      },
-      polygonStart: function() {
-        stream.polygonStart();
-      },
-      polygonEnd: function() {
-        stream.polygonEnd();
-      }
-    };
+    return d3_geo_streamTransform(stream, function(x, y) {
+      y = rotate(x * d3_radians, y * d3_radians), x = y[0];
+      stream.point(x > π ? x - 2 * π : x < -π ? x + 2 * π : x, y[1]);
+    });
   }
   function d3_geo_equirectangular(λ, φ) {
     return [ λ, φ ];
@@ -3953,6 +3937,21 @@ d3 = function() {
       λ0 = λ, sinφ0 = sinφ, cosφ0 = cosφ;
     }
   }
+  d3.geo.simplify = function() {
+    var importance = 1, simplify = {
+      stream: function(stream) {
+        return d3_geo_streamTransform(stream, function(x, y, z) {
+          if (z >= importance) stream.point(x, y);
+        });
+      },
+      importance: function(_) {
+        if (!arguments.length) return importance;
+        importance = +_;
+        return simplify;
+      }
+    };
+    return simplify;
+  };
   function d3_geo_azimuthal(scale, angle) {
     function azimuthal(λ, φ) {
       var cosλ = Math.cos(λ), cosφ = Math.cos(φ), k = scale(cosλ * cosφ);

diff --git a/d3.min.js b/d3.min.js
diff --git a/src/geo/index.js b/src/geo/index.js
@@ -16,6 +16,7 @@ import "path-context";
 import "projection";
 import "rotation";
 import "stream";
+import "simplify";
 import "albers";
 import "albers-usa";
 import "azimuthal";

diff --git a/src/geo/path.js b/src/geo/path.js
@@ -82,16 +82,10 @@ d3.geo.path = function() {
 };
 
 function d3_geo_pathProjectStream(project) {
-  var resample = d3_geo_resample(function(λ, φ) { return project([λ * d3_degrees, φ * d3_degrees]); });
+  var resample = d3_geo_resample(function(x, y) { return project([x * d3_degrees, y * d3_degrees]); });
   return function(stream) {
-    stream = resample(stream);
-    return {
-      point: function(λ, φ) { stream.point(λ * d3_radians, φ * d3_radians); },
-      sphere: function() { stream.sphere(); },
-      lineStart: function() { stream.lineStart(); },
-      lineEnd: function() { stream.lineEnd(); },
-      polygonStart: function() { stream.polygonStart(); },
-      polygonEnd: function() { stream.polygonEnd(); }
-    };
+    return d3_geo_streamTransform(stream = resample(stream), function(x, y) {
+      stream.point(x * d3_radians, y * d3_radians);
+    });
   };
 }
diff --git a/src/geo/projection.js b/src/geo/projection.js
@@ -115,15 +115,8 @@ function d3_geo_projectionMutator(projectAt) {
 }
 
 function d3_geo_projectionRadiansRotate(rotate, stream) {
-  return {
-    point: function(x, y) {
-      y = rotate(x * d3_radians, y * d3_radians), x = y[0];
-      stream.point(x > π ? x - 2 * π : x < -π ? x + 2 * π : x, y[1]);
-    },
-    sphere: function() { stream.sphere(); },
-    lineStart: function() { stream.lineStart(); },
-    lineEnd: function() { stream.lineEnd(); },
-    polygonStart: function() { stream.polygonStart(); },
-    polygonEnd: function() { stream.polygonEnd(); }
-  };
+  return d3_geo_streamTransform(stream, function(x, y) {
+    y = rotate(x * d3_radians, y * d3_radians), x = y[0];
+    stream.point(x > π ? x - 2 * π : x < -π ? x + 2 * π : x, y[1]);
+  });
 }
diff --git a/src/geo/simplify.js b/src/geo/simplify.js
@@ -0,0 +1,18 @@
+import "geo";
+import "stream";
+
+d3.geo.simplify = function() {
+  var importance = 1, simplify = {
+    stream: function(stream) {
+      return d3_geo_streamTransform(stream, function(x, y, z) {
+        if (z >= importance) stream.point(x, y);
+      });
+    },
+    importance: function(_) {
+      if (!arguments.length) return importance;
+      importance = +_;
+      return simplify;
+    }
+  };
+  return simplify;
+};
diff --git a/src/geo/stream.js b/src/geo/stream.js
@@ -29,12 +29,11 @@ var d3_geo_streamGeometryType = {
     listener.sphere();
   },
   Point: function(object, listener) {
-    var coordinate = object.coordinates;
-    listener.point(coordinate[0], coordinate[1]);
+    listener.point.apply(listener, object.coordinates);
   },
   MultiPoint: function(object, listener) {
-    var coordinates = object.coordinates, i = -1, n = coordinates.length, coordinate;
-    while (++i < n) coordinate = coordinates[i], listener.point(coordinate[0], coordinate[1]);
+    var coordinates = object.coordinates, i = -1, n = coordinates.length;
+    while (++i < n) listener.point.apply(listener, coordinates[i]);
   },
   LineString: function(object, listener) {
     d3_geo_streamLine(object.coordinates, listener, 0);
@@ -57,9 +56,9 @@ var d3_geo_streamGeometryType = {
 };
 
 function d3_geo_streamLine(coordinates, listener, closed) {
-  var i = -1, n = coordinates.length - closed, coordinate;
+  var i = -1, n = coordinates.length - closed;
   listener.lineStart();
-  while (++i < n) coordinate = coordinates[i], listener.point(coordinate[0], coordinate[1]);
+  while (++i < n) listener.point.apply(listener, coordinates[i]);
   listener.lineEnd();
 }
 
@@ -69,3 +68,14 @@ function d3_geo_streamPolygon(coordinates, listener) {
   while (++i < n) d3_geo_streamLine(coordinates[i], listener, 1);
   listener.polygonEnd();
 }
+
+function d3_geo_streamTransform(stream, point) {
+  return {
+    point: point,
+    sphere: function() { stream.sphere(); },
+    lineStart: function() { stream.lineStart(); },
+    lineEnd: function() { stream.lineEnd(); },
+    polygonStart: function() { stream.polygonStart(); },
+    polygonEnd: function() { stream.polygonEnd(); }
+  };
+}