The aspect ratio of any image can be described as the proportional relationship between the image’s width and height.
The most common video aspect ratios we have are 4:3 which was a universal video format of the 20th century and 16:9 that is commonly known for the HD television.
We have two classes for these aspect ratios in Bootstrap:
embed-responsive embed-responsive-4by3
embed-responsive embed-responsive-16by9
Bootstrap<img> Classes
Bootstrap has the following classes for styling your image elements
.rounded: To add rounded corners to the image
.rounded-circle: To shapes the image into a circle
.img-thumbnail: To shape the image into a thumbnail
.img-fluid: To make the image responsive make it scale nicely to the parent element.