It's the rule of Thirds, a simple rule to be followed so that your subject is placed within a certain area of an imaginary grid, which splits your picture in 9 equal areas.

这就是三分法则(井字构图法)，一条简单的法则，将你的图片划分成9个相等大小的区域，把你的摄影主体放在虚构的格子线的某一交叉点。

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The rule that the part and its blank are equal in the area proves the accurate outline.

根据覆盖件和展开件面积相等的原则，验证了该展开形状的精确。

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