/**
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* echarts地图投射算法
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*
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* @desc echarts基于Canvas，纯Javascript图表库，提供直观，生动，可交互，可个性化定制的数据统计图表。
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* @author Kener (@Kener-林峰, kener.linfeng@gmail.com)
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*
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*/
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define(function() {
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// 墨卡托投射
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function _mercator() {
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var radians = Math.PI / 180;
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var scale = 500;
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var translate = [480, 250];
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function mercator(coordinates) {
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var x = coordinates[0] / 360;
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var y = -(Math.log(Math.tan(
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Math.PI / 4 + coordinates[1] * radians / 2
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)) / radians) / 360;
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return [
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scale * x + translate[0],
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scale * Math.max(-0.5, Math.min(0.5, y)) + translate[1]
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];
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}
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mercator.invert = function (coordinates) {
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var x = (coordinates[0] - translate[0]) / scale;
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var y = (coordinates[1] - translate[1]) / scale;
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return [
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360 * x,
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2 * Math.atan(Math.exp(-360 * y * radians)) / radians - 90
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];
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};
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mercator.scale = function (x) {
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if (!arguments.length) {
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return scale;
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}
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scale = +x;
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return mercator;
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};
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mercator.translate = function (x) {
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if (!arguments.length) {
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return translate;
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}
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translate = [+x[0], +x[1]];
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return mercator;
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};
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return mercator;
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}
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return _mercator;
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});
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