CDPaint - GBA Asset Suite

A painting app for pixel artists and retro game developers, built around the constraints of real hardware. It keeps the familiar Windows Paint-style workflow, but adds bit-depth enforcement, palette tools, and export helpers aimed at Game Boy Advance (GBA) development.

Try the live browser demo: https://frcynda.github.io/CDPaint/

The demo runs best in Chromium-based browsers. Gecko-based browsers (Firefox, LibreWolf, Waterfox, etc.) are noticeably slower.

Features

• Bit-depth locked painting - Lock the whole canvas to a hardware color mode: 15bpp (RGB555), 16bpp (RGB565), or 8bpp indexed with a 256-color palette. Every stroke is quantized to the active mode, and you can switch modes live to convert existing artwork.
• GBA export tools - Drag-and-drop palette index reordering (so transparency lands on the right slot), automatic splitting of 64x128 / 128x64 canvases into 64x64 front/back sprites, JASC-PAL import/export for decomp projects and Porymap, and a hardware preview of how the image will look on 15-bit output.
• Image adjustments - Channel-based HSL tuning (Master, R, Y, G, C, B, M) with a split-view comparison, color depth reduction with Floyd-Steinberg dithering and OKLab accuracy, and an edge cleaner that removes stray pixels while protecting your key colors.
• Selection tools - Magic wand with a distance-based tolerance slider (drag to live-expand), lasso and polyline selection, Shift/Ctrl/Alt boolean operations, and keyed transparency for floating selections.
• Power-user workflow - Fully rebindable hotkeys, tiled mode for seamless patterns, a free-floating canvas mode, and a 20x hover preview showing the exact pixel grid under the cursor.
• Sprite editor - Project browser for opening and saving sprite assets with exact palette and index preservation, plus a palette panel with PAL support.

Tech stack

• Vanilla JavaScript (no frameworks), Canvas 2D with WebGL fragment shaders for strokes, transforms, and quantization
• Web Workers for heavy tasks (color clustering, HSL adjustments)
• Tauri 2 for the desktop shell (Rust backend for OS integration only)

Project layout

src/          Frontend (HTML, CSS, JS modules)
src-tauri/    Tauri/Rust shell, config, icons
scripts/      Dev server, build, bundle and smoke-test tooling
tools/        Brush/palette helper scripts
test/         Algorithm tests (wand, reference implementations)

Building and running

Prerequisites: Node.js LTS, Rust, and on Windows the Visual Studio Build Tools with "Desktop development with C++".

npm install
npm run dev          # dev server at http://localhost:1420
npm run tauri:build  # desktop installer (NSIS/MSI, DMG, or AppImage/deb/rpm)
npm test             # smoke tests

Installers land in src-tauri/target/release/bundle/.

Troubleshooting

• "Command not found" - The OS prerequisites aren't on PATH yet. Re-check the install guide for your OS and restart.
• Installer folder is empty - The build failed earlier. Scroll up in the terminal, fix the first error, and run npm run tauri:build again.
• Windows SmartScreen warning - Unsigned builds show this; click "More info" then "Run anyway".
• macOS says the app is damaged - System Settings -> Privacy & Security, find the blocked app, click "Open Anyway".
• Linux AppImage won't open - chmod +x path/to/CDPaint.AppImage first.

Credits

Brush tip assets in src/brushes/ come from David Revoy's Krita brush packs, licensed under Creative Commons Attribution 4.0 (CC BY 4.0) to David Revoy, www.davidrevoy.com. Some brushes were modified locally for this project.

License

The code is MIT licensed. Some bundled assets are not covered by the MIT grant - see LICENSE for the full notice (Microsoft Paint UI replicas, David Revoy's brushes, and Pokemon-related reference assets).