> For details about the request mode, timeout, and additional request parameters for loading online images, see [`request()`](../../reference/apis/js-apis-http.md) in the HTTP module.
> **NOTE**
>
> For details about the request mode, timeout, and additional request parameters for loading online images, see [`request()`](../../reference/apis/js-apis-http.md) in the HTTP module.
| vp | Pixel unit specific to the screen density. Pixels in this unit are converted into physical pixels of the screen based on the screen pixel density. This unit is used for values whose unit is not specified.|
| fp | Font pixel, which is similar to vp and varies according to the system font size.|
| lpx | Logical pixel unit of the window. It is the ratio of the actual screen width to the logical width (configured by **[designWidth](../../quick-start/package-structure.md)**). For example, if **designWidth** is set to **720** (default value), then 1lpx is equal to 2px for a screen with an actual width of 1440 physical pixels.|
| fp | Font pixel, which is similar to vp and varies according to the system font size.|
| lpx | Logical pixel unit of the window. It is the ratio of the actual screen width to the logical width (configured by **designWidth**. For example, if **designWidth** is set to **720** (default value), then 1lpx is equal to 2px for a screen with an actual width of 1440 physical pixels.|