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* ANSI C code from the article
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* "Centroid of a Polygon"
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* by Gerard Bashein and Paul R. Detmer,
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(gb@locke.hs.washington.edu, pdetmer@u.washington.edu)
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* in "Graphics Gems IV", Academic Press, 1994
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* polyCentroid: Calculates the centroid (xCentroid, yCentroid) and area of a polygon, given its
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* vertices (x[0], y[0]) ... (x[n-1], y[n-1]). It is assumed that the contour is closed, i.e., that
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* the vertex following (x[n-1], y[n-1]) is (x[0], y[0]). The algebraic sign of the area is
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* positive for counterclockwise ordering of vertices in x-y plane; otherwise negative.
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0 for normal execution;
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1 if the polygon is degenerate (number of vertices < 3);
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2 if area = 0 (and the centroid is undefined).
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* for now we require the path to be a polyline and assume it is closed.
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int centroid(std::vector<Point> p, Point centroid, double &area) {
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Point centroid_tmp(0,0);
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for (int i(n-1), j(0); j < n; i = j, j++) {
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const double ai = cross(p[j], p[i]);
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centroid_tmp += (p[j] + p[i]) * ai; // first moment.
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centroid = centroid / (3 * atmp);
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c-file-style:"stroustrup"
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c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
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// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=99 :
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centroid.cpp
