Crate contour

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Computes isorings and contour polygons by applying marching squares to a rectangular array of numeric values.

Use the ContourBuilder) to compute for a given set of values and thresholds:

  • isolines, as a Vec of Line,
  • contour polygons, as a Vec of Contour,
  • isobands, as a Vec of Band.

The contour_rings function is a convenience function to compute ring (isoline) coordinates for a single threshold.

While contour polygons (Contour) enclose all the values above a given threshold, isobands (Band) are polygons that enclose all the values between two thresholds.

The core of the algorithm is ported from d3-contour.

§Example:
let c = ContourBuilder::new(10, 10, false); // x dim., y dim., smoothing
let res = c.contours(&vec![
    0., 0., 0., 0., 0., 0., 0., 0., 0., 0.,
    0., 0., 0., 0., 0., 0., 0., 0., 0., 0.,
    0., 0., 0., 0., 0., 0., 0., 0., 0., 0.,
    0., 0., 0., 1., 1., 1., 0., 0., 0., 0.,
    0., 0., 0., 1., 1., 1., 0., 0., 0., 0.,
    0., 0., 0., 1., 1., 1., 0., 0., 0., 0.,
    0., 0., 0., 1., 1., 1., 0., 0., 0., 0.,
    0., 0., 0., 1., 1., 1., 0., 0., 0., 0.,
    0., 0., 0., 0., 0., 0., 0., 0., 0., 0.,
    0., 0., 0., 0., 0., 0., 0., 0., 0., 0.
], &[0.5]).unwrap(); // values, thresholds

let output = serde_json::json!({
  "type": "Feature",
  "geometry": {
    "type": "MultiPolygon",
    "coordinates": [[[
      [6., 7.5], [6., 6.5], [6., 5.5], [6., 4.5],
      [6., 3.5], [5.5, 3.], [4.5, 3.], [3.5, 3.],
      [3., 3.5], [3., 4.5], [3., 5.5], [3., 6.5],
      [3., 7.5], [3.5, 8.], [4.5, 8.], [5.5, 8.],
      [6., 7.5]
    ]]],
  },
  "properties": {"threshold": 0.5},
});

assert_eq!(res[0].to_geojson(), std::convert::TryFrom::try_from(output).unwrap());

Structs§

  • Band
    An isoband has the geometry and min / max values of a contour ring, built by [ContourBuilder].
  • Contour
    A contour has the geometry and threshold of a contour ring, built by [ContourBuilder].
  • ContourBuilder
    Contours generator, using builder pattern, to be used on a rectangular Slice of values to get a Vec of Contour (uses contour_rings internally).
  • Error
    An error that can occur when computing contours.
  • Line
    A line has the geometry and threshold of a contour ring, built by [ContourBuilder].

Enums§

Functions§

  • contour_rings
    Computes isoring for the given Slice of values according to the threshold value (the inside of the isoring is the surface where input values are greater than or equal to the given threshold value).

Type Aliases§