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21 lines
346 B
21 lines
346 B
5 years ago
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export default function(polygon) {
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var i = -1,
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n = polygon.length,
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x = 0,
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y = 0,
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a,
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b = polygon[n - 1],
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c,
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k = 0;
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while (++i < n) {
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a = b;
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b = polygon[i];
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k += c = a[0] * b[1] - b[0] * a[1];
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x += (a[0] + b[0]) * c;
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y += (a[1] + b[1]) * c;
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}
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return k *= 3, [x / k, y / k];
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}
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