Unfortunately, when working with a Canvas element, or when working with nodejs, these functions are not available, making very difficult to obtain these informations.
That’s why I made the svg-path-properties library
To use with npm, just type:
npm install svg-path-properties
To use it directly from the browser, include the script and call it with the prefix spp:
<script src="https://firstname.lastname@example.org/build/path-properties.min.js"></script> spp.svgPathProperties(path(track));
First, require the library and initialize it with the path string:
var path = require("svg-path-properties"); var properties = path.svgPathProperties("M0,100 Q50,-50 100,100 T200,100");
Then, access the different properties with the different methods
Get the path total length in pixels:
var length = properties.getTotalLength();
Get the point on the path at certain length (in pixels):
var point = properties.getPointAtLength(200);
Get the tangent vector at certain length (in pixels):
var tangent = properties.getTangentAtLength(200);
Get the point position and the tangent vector at the same time (more efficient than doing it with the separate methods):
var allProperties = properties.getPropertiesAtLength(200);
Canvas path animation: A path on a map that draws itself to show a train route.
Label positioning with svg-path-properties: Isolines labeling. Finding the position and angle isn’t possible even with SVG paths alone.
Drawing streamlines from a GeoTIFF file: Marking the streamlines direction with an arrow isn’t possible if the position and tangent is unknown.
I would be very happy to know if somebody is using it and creates something with the library.