45 lines
1.3 KiB
JavaScript
45 lines
1.3 KiB
JavaScript
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import {abs, acos, asin, atan, cos, epsilon, pi, sin, tan} from "./math";
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import parallel1 from "./parallel1";
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export function rectangularPolyconicRaw(phi0) {
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var sinPhi0 = sin(phi0);
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function forward(lambda, phi) {
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var A = sinPhi0 ? tan(lambda * sinPhi0 / 2) / sinPhi0 : lambda / 2;
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if (!phi) return [2 * A, -phi0];
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var E = 2 * atan(A * sin(phi)),
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cotPhi = 1 / tan(phi);
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return [
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sin(E) * cotPhi,
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phi + (1 - cos(E)) * cotPhi - phi0
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];
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}
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// TODO return null for points outside outline.
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forward.invert = function(x, y) {
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if (abs(y += phi0) < epsilon) return [sinPhi0 ? 2 * atan(sinPhi0 * x / 2) / sinPhi0 : x, 0];
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var k = x * x + y * y,
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phi = 0,
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i = 10, delta;
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do {
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var tanPhi = tan(phi),
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secPhi = 1 / cos(phi),
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j = k - 2 * y * phi + phi * phi;
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phi -= delta = (tanPhi * j + 2 * (phi - y)) / (2 + j * secPhi * secPhi + 2 * (phi - y) * tanPhi);
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} while (abs(delta) > epsilon && --i > 0);
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var E = x * (tanPhi = tan(phi)),
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A = tan(abs(y) < abs(phi + 1 / tanPhi) ? asin(E) * 0.5 : acos(E) * 0.5 + pi / 4) / sin(phi);
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return [
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sinPhi0 ? 2 * atan(sinPhi0 * A) / sinPhi0 : 2 * A,
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phi
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];
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};
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return forward;
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}
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export default function() {
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return parallel1(rectangularPolyconicRaw)
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.scale(131.215);
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}
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