Simple UI: Customizing Home Screen Wallpapers

1. Where wallpaper files live

Purpose	Path	Formats
Default wallpaper folder	koreader/settings/simpleui/sui_wallpapers/	See section 2

Platform base paths:

Kobo: /mnt/onboard/.adds/koreader/settings/simpleui/
Kindle: /mnt/us/koreader/settings/simpleui/
Android: koreader/settings/simpleui/ on internal storage

You can also pick an image from anywhere on the device with Browse… in the Wallpaper menu. That file does not have to sit under sui_wallpapers/. The folder above is only the default, convenient place that SimpleUI scans for the quick-pick list.

After adding files to sui_wallpapers/, reopen Select Wallpaper (or restart KOReader) so the list refreshes. Browse… applies immediately.

2. Supported formats

SimpleUI accepts these extensions (case-insensitive):

Extension	Notes
.jpg / .jpeg	Common choice for photos
.png	Supports transparency (painted over the normal UI background)
.bmp	Uncompressed; large files use more RAM
.gif	Still frame (not animated as wallpaper)
.webp	Supported when KOReader’s image stack can decode it on your build

There is no SVG wallpaper path in the wallpaper module (unlike icons). Prefer a raster image sized for your screen.

Design tips for e-ink

Prefer light, low-contrast backgrounds if text sits on top of the image; use Lighten (section 4) if text is hard to read.
Match portrait and landscape separately if you rotate often, or enable Auto-rotate.
Very large photos work but are scaled in memory; roughly screen resolution (e.g. 1072×1448 on many Kobos) is enough.
Dark, busy textures make module text and covers harder to read unless you lighten the wallpaper.

1. Where wallpaper files live

2. Supported formats

Design tips for e-ink

3. Enabling and choosing a wallpaper