Hello everyone!

I've released a new plugin that allows you to remove the rainbow artifacts on color e-readers such as the Kobo Libra Color, Kobo Clara Color, Kindle Colorsoft, and Pocketbook Inkpad Color 3. It adds an option called "Derainbow" which allows you to remove them directly on your device. This is most useful for black and white comics and manga.

How does it work?

It's similar to the "Reduce rainbow effect" toggle found in the official Kobo software, but it doesn't blur the image and keeps its sharpness. It uses the same method found in Kindle Comic Converter which is the use of discrete Fourier transforms. You can also make it turn on automatically with either profiles or by holding down on the option to set its default value.

There is only a slight delay for rendering new pages, but the automatic pre-rendering of pages makes this unnoticeable when reading. Performance may be improved in future releases.

Where do I get it?

To install/update the plugin, you can look at the releases page.
I only own the Kobo Libra Color, so I couldn't properly test how well it works on other devices, but if there are any problems you may create an issue on the repository.

Credits

Most of the heavy lifting was done by Its-my-right and their patch for the Inkpad Color 3 as well as their work in Kindle Comic Converter, and the idea to use Fourier transforms came from Blendman974. The above image (to the left) showing the rainbow artifacts is from this blog post by Renkon.

Links

If you want to support me, you can star my repository or buy me a coffee. :D

Repository: https://github.com/Euphoriyy/derainbowify.koplugin
Releases: https://github.com/Euphoriyy/derainbowify.koplugin/releases
Issues: https://github.com/Euphoriyy/derainbowify.koplugin/issues
Ko-fi: https://ko-fi.com/euphoriyy

Hey all!

I've now released version 1.5.0 of the Appearance plugin. This is a major release that has been a long time coming. Here are some of the features and changes made ever since v1.3.3:

Expanded customization

• Highlight color menu that allows you to customize each color and set the default color directly in the UI
• Book link color setting integrated into themes, with reset options (Suggested by Gold-Part4688).
• Progress bar customization (colors, full rounded style)

UI and font improvements

• Optional system font support (fixed)
• A menu for dictionary font replacement
• More consistent font/color application across UI elements
• Improved visibility in the color picker with a border around the wheel

Background images and transparency

• Background images now fully support transparency for enhanced visibility (Suggested by SoCal1618)
• Quick switch to last background image + capped history
• Dispatcher actions for setting the background image
• New setting for a transparent SimpleUI bottom bar (Suggested by osoatwork)
• Better SimpleUI homescreen integration (with fixes)

New plugin management

• Added menus with settings and a new About page
• In-plugin updater with optional background update checks (Suggested by Sufficient-Screen352)
• Option to reset/delete all plugin settings (with the official KOReader menu in the nightly)

Reading experience

• Footnote popups now follow book background and font colors (Requested by HappyCulture5284)
• Improved handling of fixed-layout vs reflowable documents

Under the hood

• Settings migration system for safer updates
• General performance improvements and reduced unnecessary redraws

To install/update the plugin and for a full list of changes, you can look at the releases page!

If you are using SimpleUI, make sure to always use the latest version of SimpleUI with Appearance to avoid unexpected glitches or bugs.

I am always welcome to feedback, so if you have any issues or suggestions, please leave a comment or make issues on GitHub.

If you want to support me, you can star my repository or buy me a coffee. :D

Repository: https://github.com/Euphoriyy/appearance.koplugin
Releases: https://github.com/Euphoriyy/appearance.koplugin/releases
Issues: https://github.com/Euphoriyy/appearance.koplugin/issues
Ko-fi: https://ko-fi.com/euphoriyy