32 lines
888 B
JavaScript
32 lines
888 B
JavaScript
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import {geoProjection as projection} from "d3-geo";
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import {abs, asin, cos, epsilon, halfPi, pi, sin, sqrt} from "./math";
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export function mtFlatPolarSinusoidalRaw(lambda, phi) {
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var A = sqrt(6 / (4 + pi)),
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k = (1 + pi / 4) * sin(phi),
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theta = phi / 2;
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for (var i = 0, delta; i < 25; i++) {
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theta -= delta = (theta / 2 + sin(theta) - k) / (0.5 + cos(theta));
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if (abs(delta) < epsilon) break;
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}
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return [
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A * (0.5 + cos(theta)) * lambda / 1.5,
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A * theta
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];
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}
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mtFlatPolarSinusoidalRaw.invert = function(x, y) {
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var A = sqrt(6 / (4 + pi)),
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theta = y / A;
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if (abs(abs(theta) - halfPi) < epsilon) theta = theta < 0 ? -halfPi : halfPi;
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return [
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1.5 * x / (A * (0.5 + cos(theta))),
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asin((theta / 2 + sin(theta)) / (1 + pi / 4))
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];
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};
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export default function() {
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return projection(mtFlatPolarSinusoidalRaw)
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.scale(166.518);
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}
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