Preferences

Helios allows the user to specify certain preferences. The preferences are set to reasonable defaults and users may change them as they wish.

A general overview of each option is described here

Image Resolution

This determines the size of the images requested from Helioviewer. All supported data sources use square images, so the resolutions are all square sizes.

This setting is the maximum image size that will be downloaded, and will only be used if the underlying data supports it. For example, LASCO data is natively 1k, so if your preference is set to 4k, downloaded LASCO images will use their native 1k, while SDO data will show at 4k.

This is one method you can use to control your quality/bandwidth ratio.

Format

This is the image format to use when requesting images.

• png is a lossless image format, and it will provide the highest quality image at the highest bandwidth cost.
• jpg is a lossy compression format which is ubiquitous on the web. It provides a very good quality image at a relatively low bandwidth cost compared to png.
• webp is another lossy image format which is supported by most modern browsers. The image quality is better than jpg and it uses a little more bandwidth.

This is another way for you to control your quality/bandwidth ratio.

Developer Notes

The preferences API lives in src/API/preferences.ts this is where preferences are loaded and saved from localStorage.

For the preferences UI, see src/UI/navigation/control_tabs/preference_controls.tsx

In general, preferences should only be imported and used at the UI level. The core code which handles loading images and rendering should not read preferences directly, but should instead take these options as input parameters.