Merge pull request #1788 from twpayne/interpolate-m

getCoordinateAtM for MultiLineStrings

src/ol/geom/flatgeom.js

@@ -310,16 +310,13 @@ ol.geom.flat.lineStringInterpolate =
  * @param {number} offset Offset.
  * @param {number} end End.
  * @param {number} stride Stride.
- * @param {ol.geom.GeometryLayout} layout Layout.
  * @param {number} m M.
  * @param {boolean} extrapolate Extrapolate.
  * @return {ol.Coordinate} Coordinate.
  */
 ol.geom.flat.lineStringCoordinateAtM =
-    function(flatCoordinates, offset, end, stride, layout, m, extrapolate) {
-  if ((layout != ol.geom.GeometryLayout.XYM &&
-       layout != ol.geom.GeometryLayout.XYZM) ||
-      end == offset) {
+    function(flatCoordinates, offset, end, stride, m, extrapolate) {
+  if (end == offset) {
     return null;
   }
   var coordinate;
@@ -374,6 +371,60 @@ ol.geom.flat.lineStringCoordinateAtM =
 };
 
 
+/**
+ * @param {Array.<number>} flatCoordinates Flat coordinates.
+ * @param {number} offset Offset.
+ * @param {Array.<number>} ends Ends.
+ * @param {number} stride Stride.
+ * @param {number} m M.
+ * @param {boolean} extrapolate Extrapolate.
+ * @param {boolean} interpolate Interpolate.
+ * @return {ol.Coordinate} Coordinate.
+ */
+ol.geom.flat.lineStringsCoordinateAtM = function(
+    flatCoordinates, offset, ends, stride, m, extrapolate, interpolate) {
+  if (interpolate) {
+    return ol.geom.flat.lineStringCoordinateAtM(
+        flatCoordinates, offset, ends[ends.length - 1], stride, m, extrapolate);
+  }
+  var coordinate;
+  if (m < flatCoordinates[stride - 1]) {
+    if (extrapolate) {
+      coordinate = flatCoordinates.slice(0, stride);
+      coordinate[stride - 1] = m;
+      return coordinate;
+    } else {
+      return null;
+    }
+  }
+  if (flatCoordinates[flatCoordinates.length - 1] < m) {
+    if (extrapolate) {
+      coordinate = flatCoordinates.slice(flatCoordinates.length - stride);
+      coordinate[stride - 1] = m;
+      return coordinate;
+    } else {
+      return null;
+    }
+  }
+  var i, ii;
+  for (i = 0, ii = ends.length; i < ii; ++i) {
+    var end = ends[i];
+    if (offset == end) {
+      continue;
+    }
+    if (m < flatCoordinates[offset + stride - 1]) {
+      return null;
+    } else if (m <= flatCoordinates[end - 1]) {
+      return ol.geom.flat.lineStringCoordinateAtM(
+          flatCoordinates, offset, end, stride, m, false);
+    }
+    offset = end;
+  }
+  goog.asserts.fail();
+  return null;
+};
+
+
 /**
  * @param {Array.<number>} flatCoordinates Flat coordinates.
  * @param {number} offset Offset.

src/ol/geom/linestring.js

@@ -81,14 +81,26 @@ ol.geom.LineString.prototype.closestPointXY =
 
 
 /**
+ * Returns the coordinate at `m` using linear interpolation, or `null` if no
+ * such coordinate exists.
+ *
+ * `opt_extrapolate` controls extrapolation beyond the range of Ms in the
+ * MultiLineString. If `opt_extrapolate` is `true` then Ms less than the first
+ * M will return the first coordinate and Ms greater than the last M will
+ * return the last coordinate.
+ *
  * @param {number} m M.
  * @param {boolean=} opt_extrapolate Extrapolate.
  * @return {ol.Coordinate} Coordinate.
  */
 ol.geom.LineString.prototype.getCoordinateAtM = function(m, opt_extrapolate) {
+  if (this.layout != ol.geom.GeometryLayout.XYM &&
+      this.layout != ol.geom.GeometryLayout.XYZM) {
+    return null;
+  }
   var extrapolate = goog.isDef(opt_extrapolate) ? opt_extrapolate : false;
   return ol.geom.flat.lineStringCoordinateAtM(this.flatCoordinates, 0,
-      this.flatCoordinates.length, this.stride, this.layout, m, extrapolate);
+      this.flatCoordinates.length, this.stride, m, extrapolate);
 };
 
 

src/ol/geom/multilinestring.exports

@@ -1,5 +1,6 @@
 @exportSymbol ol.geom.MultiLineString
 @exportProperty ol.geom.MultiLineString.prototype.clone
+@exportProperty ol.geom.MultiLineString.prototype.getCoordinateAtM
 @exportProperty ol.geom.MultiLineString.prototype.getCoordinates
 @exportProperty ol.geom.MultiLineString.prototype.getLineStrings
 @exportProperty ol.geom.MultiLineString.prototype.getType

src/ol/geom/multilinestring.js

@@ -78,6 +78,41 @@ ol.geom.MultiLineString.prototype.closestPointXY =
 };
 
 
+/**
+ * Returns the coordinate at `m` using linear interpolation, or `null` if no
+ * such coordinate exists.
+ *
+ * `opt_extrapolate` controls extrapolation beyond the range of Ms in the
+ * MultiLineString. If `opt_extrapolate` is `true` then Ms less than the first
+ * M will return the first coordinate and Ms greater than the last M will
+ * return the last coordinate.
+ *
+ * `opt_interpolate` controls interpolation between consecutive LineStrings
+ * within the MultiLineString. If `opt_interpolate` is `true` the coordinates
+ * will be linearly interpolated between the last coordinate of one LineString
+ * and the first coordinate of the next LineString.  If `opt_interpolate` is
+ * `false` then the function will return `null` for Ms falling between
+ * LineStrings.
+ *
+ * @param {number} m M.
+ * @param {boolean=} opt_extrapolate Extrapolate.
+ * @param {boolean=} opt_interpolate Interpolate.
+ * @return {ol.Coordinate} Coordinate.
+ */
+ol.geom.MultiLineString.prototype.getCoordinateAtM =
+    function(m, opt_extrapolate, opt_interpolate) {
+  if ((this.layout != ol.geom.GeometryLayout.XYM &&
+       this.layout != ol.geom.GeometryLayout.XYZM) ||
+      this.flatCoordinates.length === 0) {
+    return null;
+  }
+  var extrapolate = goog.isDef(opt_extrapolate) ? opt_extrapolate : false;
+  var interpolate = goog.isDef(opt_interpolate) ? opt_interpolate : false;
+  return ol.geom.flat.lineStringsCoordinateAtM(this.flatCoordinates, 0,
+      this.ends_, this.stride, m, extrapolate, interpolate);
+};
+
+
 /**
  * @return {ol.geom.RawMultiLineString} Coordinates.
  * @todo stability experimental