[APP] Kinbo – Mobile-first Manga/E-book Optimizer (Android)

[GigaCat]

Hi everyone,

I wanted to share a project I’ve been working on called Kinbo.

I’m a huge fan of Kindle Comic Converter (KCC), but I often found myself wanting to prep manga or PDFs while away from my desktop. I built Kinbo to bring that same optimization pipeline directly to Android so I could handle everything on my phone right after a download.

Main Features:

• Smart Margin Cropping: Automatically detects and trims borders to maximize art on 6" and 7" screens.
• Spread Splitting: Logic to detect and split double-page spreads into portrait or rotate them.
• Native KEPUB Export: Built-in support for Kobo’s KEPUB format.
• AI Upscaling: On-device sharpening for lower-resolution scans.
• Batch Processing: Handles entire folders or series in the background.

Current Limitations:
Please note that AZW3 and MOBI are not yet supported. I’m currently focusing on the EPUB/KEPUB and PDF pipelines first.

Technical Note:
The app is built in Kotlin. I’ve implemented a parallel processing pipeline to keep it stable even on mid-range devices without hitting the Android Low Memory Killer.

Google Play Store:
https://play.google.com/store/apps/d...inbo.converter

Looking forward to your thoughts!

[Evil_Crab]

Any chance you can add "Rainbow eraser" feature from KCC? Colored eink screens are prone to rainbow artifacts in dithered greyscale images, such as manga.

Also, "update in place" feature and profiles for Boox devices would be handy when using the app on Android e-readers to directly optimize manga grabbed with Mihon.

[GigaCat]

Originally Posted by Evil_Crab

Any chance you can add "Rainbow eraser" feature from KCC? Colored eink screens are prone to rainbow artifacts in dithered greyscale images, such as manga.

Also, "update in place" feature and profiles for Boox devices would be handy when using the app on Android e-readers to directly optimize manga grabbed with Mihon.

Great timing! I was actually working on this feature. I have already pushed the update with rainbow effect remover and custom gamma support. It's in review and will go live within a few hours. As for the BOOX device profile, I will add them within next few days. Meanwhile you can use custom resolution switch to match the exact pixel resolution of your BOOX device.

Also can you please explain what you mean by "update in place"? I think I am misunderstanding it.

Thanks for using the app and the feedback. Feel free to request for any new features.

[Evil_Crab]

By "update in place" I meant overwriting original files with the optimized ones. Right now, if you select the same folder for both input and output, KinBo will save optimized files with " (1)" suffix, so to actually replace original files with the optimized ones, you have to export them to some other folder and then replace the original ones via file manager.

And a couple more pieces of feedback:
1. By default, on Boox devices, text on some buttons is unreadable, although it can be fixed via eink tweaks: https://imgur.com/a/AfTlOvh
2. It would be nice to have an explanation of what some of the options do (e.g., Manga mode).

[GigaCat]

Originally Posted by Evil_Crab

By "update in place" I meant overwriting original files with the optimized ones. Right now, if you select the same folder for both input and output, KinBo will save optimized files with " (1)" suffix, so to actually replace original files with the optimized ones, you have to export them to some other folder and then replace the original ones via file manager.

And a couple more pieces of feedback:
1. By default, on Boox devices, text on some buttons is unreadable, although it can be fixed via eink tweaks: https://imgur.com/a/AfTlOvh
2. It would be nice to have an explanation of what some of the options do (e.g., Manga mode).

Great info. I had no idea readability was even an issue. For now I held off the update due to a minor bug. Will update with all the fixes in couple of days.

[GigaCat]

This release focuses on making file conversion much faster and more stable, especially when the Rainbow Eraser feature is enabled.

Up to 15x Faster Conversions: Manga that previously took 5 to 7 minutes to convert with Rainbow Eraser active will now complete in under 1 minute.

Smart Concurrency Scaling: The app dynamically detects the device's processor cores and available memory to process as many pages in parallel as the hardware can safely handle.

Full Stability & Crash Protection: Memory management has been rewritten to recycle resources immediately on background threads. In addition, the app dynamically scales back page processing when outputting high-resolution documents or running on low-memory devices, preventing Out-of-Memory crashes.

[GigaCat]

Hi everyone,

KinBo v1.1.7 is now live! Here is a quick breakdown of what’s changed:

• Custom Covers: Added the ability to manually select and inject custom cover images for your conversions.
  
• CBZ Bug Fix: Resolved an issue where CBZ-to-CBZ processing caused certain pages to double up or repeat.

The update is rolling out now and should be available on your device shortly. Thanks to everyone who reported the page doubling bug!

Happy reading!

[urffsamhunt]

Hey! Great work, really appreciate it.
Are there any plans in the future for implementing the 'Custom Cropping Power' (like the one in KCC)?
It would come in handy for my use-case

[GigaCat]

Originally Posted by urffsamhunt

Hey! Great work, really appreciate it.
Are there any plans in the future for implementing the 'Custom Cropping Power' (like the one in KCC)?
It would come in handy for my use-case

Certainly! I will try to implement and push the update within this week.

[GigaCat]

Hi everyone,

We have just released an update for KinBo Comic Converter focusing on fixing a major cover page display issue on Kindle devices.

What's Fixed:
* Kindle Cover Display: Fixed an issue where custom cover images or the first page did not show up as book covers in the Kindle library view.
* EPUB 3 / Legacy Metadata Alignment: The output generator now writes all necessary descriptors required by Amazon's ingestion system (Send-to-Kindle) and local Kindle parsers:
- Added the mandatory properties="cover-image" to the manifest image item.
- Included retro-compatible <meta name="cover" content="..." /> tags in the metadata block.
- Added an epub:type="landmarks" navigation map in nav.xhtml for EPUB 3 compliance.
- Added a <guide> section to the OPF package document to support older Kindle models.

This ensures that whether you upload via Send-to-Kindle (which uses standard EPUB 3 processing) or sideload via USB, Kindle devices will correctly generate, cache, and display your comic book covers!

Let us know if you run into any issues or have feedback!

Happy reading!