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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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