gis-tools-ts
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A collection of geospatial tools primarily designed for WGS84, Web Mercator, and S2.
74 lines • 2.88 kB
JavaScript
import { pointDistance as distance } from '../../geometry/s2/point.js';
import { averageInterpolation, defaultGetInterpolateCurrentValue } from './index.js';
import { lRGBToGamma, sRGBToLinear } from '../../index.js';
/**
* # Inverse Distance Weighting Interpolation
*
* ## Description
* Given a reference of data, interpolate a point using inverse distance weighting
*
* ## Usage
* ```ts
* import { idwInterpolation, PointIndexFast } from 'gis-tools-ts';
* import type { VectorPoint } from 'gis-tools-ts';
*
* // We have m-value data that we want to interpolate
* interface TempData { temp: number; }
*
* const pointIndex = new PointIndexFast<TempData>();
* // add lots of points
* pointIndex.insertLonLat(lon, lat, data);
* // ....
*
* // given a point we are interested in
* const point: VectorPoint = { x: 20, y: -40 };
* // get a collection of points relative to the point
* const data = await pointIndex.searchRadius(point.x, point.y, radius);
*
* // interpolate
* const interpolatedValue = idwInterpolation<TempData>(point, data, (p) => p.m.temp);
* ```
* @param point - point to interpolate
* @param refData - reference data to interpolate from
* @param getValue - function to get value from reference data. Can be the z value or a property in the m-values
* defaults to function that returns the z value or 0 if the z value is undefined
* @returns - the interpolated value
*/
export function idwInterpolation(point, refData, getValue = defaultGetInterpolateCurrentValue) {
if (refData.length === 0)
return 0;
let numerator = 0;
let denom = 0;
for (const refPoint of refData) {
const d2 = Math.pow(distance(point, refPoint), 2);
const value = getValue(refPoint);
if (d2 === 0)
return value; // if distance is 0, return value
numerator += value / d2;
denom += 1 / d2;
}
return numerator / denom;
}
/**
* Helper function for {@link idwInterpolation} on RGB(A) data.
* Light in RGB data is logarithmically weighted, so we need to expand each component by n^2 to
* get the correct weight for each component.
* @param point - Point to interpolate
* @param refData - Reference data points
* @returns - The interpolated RGBA data.
*/
export function rgbaIDWInterpolation(point, refData) {
if (refData.length === 0)
return { r: 0, g: 0, b: 0, a: 255 };
const rData = idwInterpolation(point, refData, (p) => sRGBToLinear(p.m?.r ?? 0));
const gData = idwInterpolation(point, refData, (p) => sRGBToLinear(p.m?.g ?? 0));
const bData = idwInterpolation(point, refData, (p) => sRGBToLinear(p.m?.b ?? 0));
const a = averageInterpolation(point, refData, (p) => p.m?.a ?? 255);
return {
r: lRGBToGamma(rData),
g: lRGBToGamma(gData),
b: lRGBToGamma(bData),
a,
};
}
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