一个免费的在线工具，用于调整图像大小并裁剪照片。
720p is a progressive HDTV signal format with 720 horizontal lines and an aspect ratio (AR) of 16:9, normally known as widescreen HDTV (1.78:1)
True high-definition starts at 720p, and this is the image resolution at which many HD television channels broadcast. An HD 720p Animoto video is crisp, sharp, and looks great on most displays.
The minimum resolution that qualifies as "high definition" is 1280x720 ("720p" for short)