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Фото: Raghed Waked / Reuters，详情可参考爱思助手下载最新版本
Source: Computational Materials Science, Volume 267。Line官方版本下载对此有专业解读
You look at a region of the image. If all the pixels are roughly the same color (below some threshold), you store the average color for the whole region as a single value. If the pixels vary too much, you split the region into four quadrants and try again.