Optimized images

This series of articles are for NFT dApp developers and NFT creators who want to allow their audience to showcase their NFTs on the Ledger Stax device.

Ledger Stax Lock Screen

The Lock screen is the first thing users see when they pick up their Ledger Stax. The Lock Screen can be customized by choosing an image from the NFT gallery or from the user’s smartphone.

The Ledger screen has specific requirements which need to be considered:

• Dimension: The screen’s resolution is 672px (height) by 400px (width). For an optimal display of the NFT on Ledger Stax, make sure the NFT image height is 1.68x the width and the minimum width is 400px (ex: 840px * 500px).
• Color profile: The Ledger Stax screen supports up to 16 levels of gray (4-bit grayscale).

Ledger Live will give the NFT owner an option to crop the image for their NFT and the color will be converted to 4-bit grayscale, but in a lot of instances it won’t look ideal.

As a creator, you can provide a dedicated secondary image that will only be used for displaying on Ledger Stax’s lock screen. As an example, for the [ Ledger ] Market Pass - Genesis Edition NFT, you can see below the primary image against the secondary image that has been designed for Ledger Stax.

Primary Image	Secondary Image

Use Dithermark To Convert Your Image

Converting your image to black and white is not enough. To ensure that your final output will look great on Ledger Stax, you can use Dithermark, a free tool, to apply the same dithering algorithm and color profile that your image will be converted to for display on Ledger Stax.

Here’s how to use it:

1. Make sure your image aspect ratio matches that of Ledger Stax
2. Go to app.dithermark.com and upload your image
3. On the Color Dither tab, make the following selections:
   • a. Algorithm: Floyd-Steinberg
   • b. Color comparison: RGB
   • c. Color palette: Monochrome
   • d. Color count: 16
4. Go to the Export tab and click “Save”

Your image is now ready to be added to your NFT’s metadata!

Introducing the Ledger Stax metadata

In order to showcase NFTs on Ledger Stax (with the dedicated secondary image), we’ve created a new schema for metadata ledger_stax_image that points to the location of the file where the Ledger Stax image is stored.

The metadata schema is open to all. As a dApp developer, you can create a flow where end-users will upload an image for Ledger Stax which will then trigger the metadata update.

To update your NFT metadata, you have two options:

1. Use the Ledger Stax Metadata tool (for non-technical users and advanced users with immutable metadata); read our how-to article next
2. Update your metadata manually (for advanced users with mutable metadata); read the technical details