基本概念

顶线(top)
中线(middle)
基线(baseline)
底线(bottom)

行距(line-height)———— 两行文字任意一条线的距离

font-size ———— 顶线到底线

CSS3 object-fit/object-position - CR

Method of specifying how an object (image or video) should fit inside its box. object-fit options include “contain” (fit according to aspect ratio), “fill” (stretches object to fill) and “cover” (overflows box but maintains ratio), where object-position allows the object to be repositioned like background-image does.

不支持IE11