https://github.com/bbbbbr/gameboy_qr_paint

Draw on the Game Boy and share it direct to your phone using a QRCode! (without the internet!)
https://github.com/bbbbbr/gameboy_qr_paint

gameboy gameboy-color gbdk gbdk-2020 pixel-art pixelart qr-code qrcode

Last synced: 22 days ago
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Draw on the Game Boy and share it direct to your phone using a QRCode! (without the internet!)

• Host: GitHub
• URL: https://github.com/bbbbbr/gameboy_qr_paint
• Owner: bbbbbr
• License: other
• Created: 2026-01-25T11:09:01.000Z (3 months ago)
• Default Branch: main
• Last Pushed: 2026-03-24T07:20:12.000Z (about 1 month ago)
• Last Synced: 2026-03-25T08:38:04.819Z (about 1 month ago)
• Topics: gameboy, gameboy-color, gbdk, gbdk-2020, pixel-art, pixelart, qr-code, qrcode
• Language: C
• Homepage:
• Size: 1.3 MB
• Stars: 24
• Watchers: 0
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • Changelog: Changelog.md
  • License: LICENSE

Awesome Lists containing this project

README

          

# GameBoy QR-Paint

bbbbbr 2026

## Overview

Draw on the Game Boy / Mega Duck and share it direct to your phone using a QRCode!

(without the internet!)

### ROM

Downloadable ROM available on itch: https://bbbbbr.itch.io/game-boy-qr-paint

![Photograph of QR Paint on a Game Boy Color with a drawing of a dogcow](/info/qrpaint_0.90_dogcow_on_cgb_sm.jpg)

![Photograph of QR Paint showing a QRCode on a Game Boy Color which encodes the dogcow drawing, and a mobile phone showing the transferred image in a web browser](/info/qrpaint_0.90_dogcow_qrcode_on_cgb_and_mobile_sm.jpg)

## Features

- Share drawings as PNG images via QRCode

- Drawing tools: Pencil, Line, Eraser, Rectangle, Circle, Flood Fill, Spray

- Undo, Redo stack

- 3 Drawing Save slots

- Adjustable Draw Width

- Adjustable Draw speed (Fast, Medium, Slow, Pixel Step)

- 2 Draw colors (Black and White)

- SNES Mouse support through Super Game Boy (SGB)

- Inside Gadgets USB Mouse link adapter Support, supported on MiSTer (Game Boy)

- Game Boy Printer support

- Mega Duck Printer support

## Usage

Button Controls:

- `D-Pad`: Move cursor

- `A`: Draws with tool

- `B`:

  - Short Press: Cancel tool action / Teleport cursor between menu and draw areas

  - Hold Down: Move faster in draw area

- `SELECT + UP/DOWN`: Adjust Cursor Speed

- `SELECT + LEFT/RIGHT`: Adjust Drawing Width

- `START`: Create QRCode

The cursor movement has a small amount of inertia while in the drawing areas.

It will apply as long as some button is being held down, and resets to zero

when all buttons are released. This helps with drawing curves using a D-Pad,

which otherwise tends toward right angles and diagonals.

## Sending to Mobile Phone

### Scanners

Known **working** QRCode scanners:

- Android Binary Eye

- Android Camera (in scan mode)

- Web: https://scanqr.org

Known **not working** scanners:

- "Camera" app on some Samsung phones

- Default "Camera" app on iOS

### Browsers

Known **working** Browsers:

(via "share-to" or pasting in the url, not via the browser's own scanner)

- Firefox/Fennec Web Browser (Android mobile, Linux desktop)

- Chromium (Linux desktop)

Known **not working** Browsers:

- Chromium/Chrome (Android)

## SGB + SNES Mouse

Super Nintendo Mouse support through the SGB is based on a modified version of

vinheim3's demo. Thanks for sharing your cool idea and how do it!

- The OEM SNES mouse works well at the qr-paint "medium" speed.

- The Hyperkin SNES mouse works better at qr-paint "slow" setting.

For emulators, it's verified as working in Mesen. 

The SNES mouse should be second controller, it may be a little fast.

# USB Mouse

USB Mouse support is available when using the Inside Gadgets USB Keyboard

link adapter with [modified firmware](https://github.com/bbbbbr/CH559sdccUSBHost/tree/ig_mouse_adapter)

that adds mouse support. The MiSTer Game Boy core can optionally emulate

this link port accessory, including the mouse support.

## Mega Duck

QR-Paint can only be used on the Mega Duck when Cart SRAM is available.

This is possible when using:

- A laptop with the add-on Memory Cart in the secondary cart slot (use duck.md2 build)

- A GB->Duck cart slot adapter and an MBC5 cart (use duck.mbc5 build)

- A cart with built-in SRAM (the ManCloud flash cart) (use duck.md2 build)

To run in an emulator, use:

- `superjunior_sameduck --duck-printer-1pass --duck-sram-cart qr_paint.duck.md2`

This requires `SuperJuniorSameDuck v1.0.1`:

- https://github.com/bbbbbr/SuperJuniorSameDuck/releases/tag/Duck_v1.0.1

## Technical details

The drawing is limited to 96x96 monochrome pixels due to QRCode

size limits and the current lack of PNG DEFLATE compression.

The process is:

- Convert: GB Drawing -> Indexed PNG -> Base64 Encode -> mime url -> QRCode

- Share to phone: QRCode -> Scanner app -> Share to Web Browser

## The Emulator .sav files are PNGs! 

The `.sav` files generated by emulators for this ROM can be opened in many paint

programs since the first cart SRAM bank contains an indexed PNG of the last

drawing image that was exported as a QRCode.

## Dev Tools Used

- GBDK-2020 (4.5.0+)

- Emulicious

- ImHex

- pngcheck

The QRCode generator is an optimized fork of https://github.com/bbbbbr/gameboy_qrcode which is a fork of msx_qrcode https://github.com/MartinezTorres/msx_qrcode/tree/master

Which in turn is a fork of Nayuki's QR Code: https://github.com/nayuki/QR-Code-generator