DEV Community: fan ei

Show DEV: SmartScan — Open Source Android Document Scanner

fan ei — Wed, 15 Apr 2026 02:23:25 +0000

What I Built

SmartScan is a fully open source document scanner for Android built with Kotlin.

Features

Document scanning with edge detection
PDF generation
QR Code scanning and generation
OCR text recognition (powered by ML Kit)
Document signing and annotation
Completely offline capable

Tech Stack

Language: Kotlin
Min SDK: Android 7.0 (API 24)
Camera: CameraX
Image Processing: OpenCV
OCR: Google ML Kit
PDF: iText 7
Architecture: MVVM + Clean Architecture

Why Open Source

There are plenty of scanner apps on the Play Store, but most of them are:

Ad-heavy with intrusive pop-ups
Watermark everything behind a paywall
Bloated with unnecessary features
Not transparent about data handling

I wanted to build something different — a scanner app that respects users.

The Code

GitHub: https://github.com/fanei/scan

Contributions, issues, and PRs are welcome!

Try It

Google Play: https://play.google.com/store/apps/details?id=com.smartscan.smartscan

100% free. No ads. No watermarks. Open source.

Stats So Far

Users in 8+ countries (Nigeria, Ethiopia, Indonesia, Kenya, Philippines, and more)
0% crash rate
75% install conversion rate

Naija, Stop Paying for Document Scanners — Here is a Free Alternative

fan ei — Wed, 15 Apr 2026 02:22:35 +0000

How Much Are You Spending on Scanning?

Every semester, Nigerian students spend thousands of Naira at cyber cafés just to scan documents — JAMB forms, admission letters, course registration, certificates.

And the scanner apps on Google Play? Most of them are frustrating:

Full of pop-up ads every 2 seconds
Watermarks covering your important documents
"Premium" features locked behind a paywall
Heavy apps that drain your data and battery

I Built Something Better

SmartScan is a free Android app that does one thing well: scan your documents into clean PDFs. No catch.

What It Does

Scan to PDF — Point your camera, get a professional PDF
QR Code Scanner — Scan payment codes, class schedules, event tickets
OCR — Turn printed text into editable digital text
Sign Documents — Add your signature on any PDF
Works Offline — No data needed. Scan anywhere, anytime
Small Size — Less than 15MB. Won't eat your storage

Why It Is Different

Zero ads. Not "minimal ads" — literally zero
No watermarks. Your documents stay clean
No premium tier. Everything is free
Works on low-end Android phones (Android 7.0+)

Built for Nigerian Students

I know data is expensive in Nigeria. That is why SmartScan:

Works completely offline
Has a small APK size
Does not run background processes that drain your battery

Download Now

Google Play: https://play.google.com/store/apps/details?id=com.smartscan.smartscan

It is free. It will always be free. No tricks.

Share With Your Classmates

If this helps you, share it with someone who needs it. Every Nigerian student deserves free tools.

GitHub: https://github.com/fanei/scan

How I Built an Open Source Android Document Scanner with Kotlin

fan ei — Tue, 14 Apr 2026 11:29:00 +0000

Introduction

Building a document scanner app seems complex — edge detection, perspective correction, PDF generation, OCR. But with modern Android development tools, it's more approachable than you think.

Here's how I built SmartScan, a fully open source document scanner app using Kotlin.

Architecture

The app follows clean architecture principles:

Presentation Layer — MVVM with ViewModels and Compose UI
Domain Layer — Use cases for scan, OCR, and export operations
Data Layer — Room database for document storage, CameraX for capture

Key Technical Decisions

CameraX for Document Capture

CameraX makes camera integration straightforward. For a scanner app, the key is handling the preview and capture lifecycle correctly.

OpenCV for Edge Detection

Edge detection is the core of any scanner app. I used OpenCV's Canny edge detection combined with contour finding:

val gray = Mat()
Imgproc.cvtColor(original, gray, Imgproc.COLOR_RGBA2GRAY)
Imgproc.Canny(gray, edges, 50.0, 150.0)

PDF Generation with iText

For PDF creation, iText provides a robust API. The challenge was keeping the library size reasonable — I used iText 7 core module only.

OCR with ML Kit

Google's ML Kit makes on-device OCR simple and accurate. It works offline, which is crucial for users in areas with limited connectivity.

Challenges

Performance on low-end devices — Had to optimize image processing to avoid OOM errors
Camera compatibility — Different Android OEMs implement camera APIs differently
APK size — Kept it under 15MB by using modular dependencies
Offline OCR — ML Kit handles this well but language packs add size

What I Learned

Start with MVP features (scan + save)
Optimize for the weakest devices your users have
Test on real devices, not just emulators
Offline-first is not optional for emerging markets

Open Source

The full source code is available: https://github.com/fanei/scan

Contributions, issues, and suggestions are welcome!

Try the App

Google Play: https://play.google.com/store/apps/details?id=com.smartscan.smartscan

100% free, no ads, no watermarks. Built for everyone.

Why Every Student in Africa Needs a Free Document Scanner App

fan ei — Tue, 14 Apr 2026 11:28:16 +0000

The Problem

As a student in Nigeria, Ghana, Kenya, or anywhere in Africa, you deal with paper every day. Lecture notes, assignment sheets, ID cards, certificates. And what do you do when you need a digital copy?

You either:

Pay someone at a cyber café
Use a scanner app that covers your document with watermarks
Suffer through endless ads just to save one PDF

This is broken.

The Solution

I built SmartScan — a completely free document scanner for Android.

No ads. No watermarks. No "premium" tricks. Just scan, save, share.

Features Students Actually Need

Scan to PDF — Point your camera, get a clean PDF
QR Code Scanner — Scan class schedules, payment codes
OCR Text Recognition — Turn handwritten notes into editable text
Works Offline — No internet? No problem. Scan anywhere
Small App Size — Only a few MB, won't eat your storage
Sign Documents — Add your signature on any document

Why Free?

Because students shouldn't have to pay to digitize their own notes. Education tools should be accessible to everyone, regardless of their budget.

Built for Your Phone

SmartScan is optimized for the Android phones most students actually use — not just the latest flagship. It works on Android 7.0 and up with minimal resources.

Tech Details

Built with Kotlin for Android. Open source. Contributions welcome.

Download

Available on Google Play: https://play.google.com/store/apps/details?id=com.smartscan.smartscan

GitHub (star it if you like it!): https://github.com/fanei/scan

Spread the Word

If you found this useful, share it with a classmate. Every student deserves free tools.

I Built a 100% Free Document Scanner App — No Ads, No Watermarks

fan ei — Fri, 10 Apr 2026 07:41:29 +0000

Why I Built SmartScan

Every document scanner app I've tried is the same: ads everywhere, watermarks on every page, and a paywall hiding basic features. So I built my own.

What It Does

SmartScan is a completely free Android app that lets you:

Scan documents to PDF — Fast edge detection, multi-page support
QR Code Generator & Scanner — Create and scan QR codes instantly
OCR Text Recognition — Extract text from images
Edit & Sign Documents — Add signatures, annotations
Share anywhere — Export as PDF or image

What Makes It Different

100% free
Zero ads
No watermarks
No account required
Open source (Kotlin/Android)

Tech Stack

Built natively with Kotlin for Android. Source code available on GitHub.

Try It

Google Play: https://play.google.com/store/apps/details?id=com.smartscan.smartscan

GitHub: https://github.com/fanei/scan

I'd love to hear your feedback! What features would you want in a scanner app?