直方图给出了一个简单可见的指示，可以用来判断一幅图像是否合理的利用了全部被允许的灰度级范围。一般一幅图应该利用全部或几乎全部可能的灰度级，否则等于增加了量化间隔。丢失的信息将不能恢复。-Histogram shows a simple visible indication, an image can be used to determine the reasonableness of the use of all the allowed range of gray levels. A map should be used generally all or almost all possible gray level, or equivalent to a quantitative increase in the interval. Missing information will not be restored.