The fill() method closes any subpaths and then fills each subpath in turn using fillStyle (which can be a color, or, as discussed later, a gradient object) to determine how to draw the fill.

fill() 方法使所有子路径封闭起来，然后逐个填充每个子路径，期间使用 fillStyle （一种颜色，或一个渐变对象）来决定如何绘制填充。

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An object that specifies a mapping between color column values and colors or a gradient scale.

一个对象，它指定列的颜色值和颜色或渐变刻度之间的映射。

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LED light source color changes in nature, can be a single color or by the electronic controller to do all sorts of gradient color change, rich enterprise signs can look and readability.

LED光源色彩变化性大，可做单一色彩或利用电子调控器做多种渐层颜色变化，丰富企业招牌可看性及可读性。

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