CSS：伪元素：在继承原始元素的宽度/高度之前和之后

I am using the css pseudo elements :before and :after to give an indent-effect on some of my images on a website. However without specifying the width and height, these won't display. This would have me specifying a fixed width and height for each of the images, which I guess would work for a static webpage.I am using the css pseudo elements :before and