Candle Annotator

A web-based tool for manually annotating candlestick charts with pattern labels and trend lines. Built for creating labeled training data for machine learning models in trading analysis.

Overview

Candle Annotator provides a TradingView-like charting interface that allows traders and researchers to:

• Upload historical OHLC (Open, High, Low, Close) candle data from CSV files
• Visualize candlestick charts with interactive zoom and pan
• Mark breakout patterns (Break Up, Break Down) directly on candles
• Draw custom trend lines with two-click interaction
• Delete annotations with a dedicated tool
• Export all annotations as CSV for ML training pipelines

Features

Data Management

• CSV Upload: Import OHLC data with support for both Unix timestamps and date strings
• SQLite Storage: All candle data and annotations stored locally in SQLite database
• Data Persistence: Annotations and candles persist between sessions

Chart Visualization

• Interactive Candlestick Chart: Powered by lightweight-charts library
• Dark Theme: Eye-friendly slate color scheme
• Zoom & Pan: Mouse wheel zoom and drag-to-pan functionality
• Crosshair: Precise price and time tracking

Annotation Tools

• Break Up Markers: Green arrow markers below candles indicating upward breakouts
• Break Down Markers: Red arrow markers above candles indicating downward breakouts
• Trend Lines: Two-click line drawing with real-time preview
• Delete Tool: Remove any annotation (markers or lines) by clicking on them
• Tool Toggle: Click tool button again to deactivate

Export

• CSV Export: Download all annotations with timestamp, label type, and price data
• ML-Ready Format: Structured data suitable for training ML models

Tech Stack

• Frontend: Next.js 16 (App Router), React 19, TypeScript
• Styling: Tailwind CSS 3, shadcn/ui components
• Charting: lightweight-charts 4.x (TradingView)
• Icons: lucide-react
• Backend: Next.js API Routes
• Database: SQLite with better-sqlite3
• ORM: Drizzle ORM
• CSV Parsing: papaparse

Getting Started

Prerequisites

• Node.js 18.x or higher
• npm 9.x or higher
• Build tools for native modules (see DEPLOYMENT.md)

Installation

1. Clone the repository:

   git clone <repository-url>
   cd candle_annotator
   

2. Install dependencies:

   npm install
   

3. Start the development server:

   npm run dev
   

4. Open http://localhost:3000 in your browser

Usage

1. Upload Data: Click "Choose CSV File" and select a CSV with columns: time,open,high,low,close
2. View Chart: The candlestick chart renders automatically after upload
3. Add Annotations:
   • Click "Label: Break Up" or "Label: Break Down" then click on a candle
   • Click "Draw Line" then click two points to draw a trend line
   • Press Escape to cancel line drawing
4. Delete Annotations: Click "Delete" tool, then click on markers or lines to remove them
5. Export: Click "Export CSV" to download all annotations

CSV File Format

Input Format

Your CSV file should have these columns:

time,open,high,low,close
1700000000,1.0500,1.0520,1.0490,1.0510
1700000060,1.0510,1.0530,1.0505,1.0525

Time column accepts:

• Unix timestamps (seconds): 1700000000
• Date strings: 2024-01-15, 2024-01-15 10:30:00

Export Format

The exported CSV includes:

timestamp,label_type,price
1700000000,break_up,1.0510
1700000120,break_down,1.0505
1700000000,line,1.0500

• timestamp: Unix timestamp of the annotation
• label_type: break_up, break_down, or line
• price: Close price for markers, start price for lines

Database Schema

Candles Table

{
  id: integer (PK, auto-increment),
  time: integer (Unix timestamp, unique),
  open: real,
  high: real,
  low: real,
  close: real
}

Annotations Table

{
  id: integer (PK, auto-increment),
  timestamp: integer (Unix timestamp),
  label_type: text ('break_up' | 'break_down' | 'line'),
  geometry: text (JSON string for line coordinates, null for markers),
  created_at: integer (Unix timestamp)
}

API Endpoints

POST /api/upload

Upload CSV file and store candle data

Request: multipart/form-data with file field
Response: { success: true, count: number } or { error: string }

GET /api/candles

Retrieve all candle records

Response: Array of candle objects ordered by time

GET /api/annotations

Retrieve all annotations

Response: Array of annotation objects with parsed geometry

POST /api/annotations

Create a new annotation

Request: { timestamp: number, label_type: string, geometry?: object }
Response: Created annotation object with ID

DELETE /api/annotations/[id]

Delete an annotation by ID

Response: { success: true } or { error: string }

GET /api/export

Export annotations as downloadable CSV

Response: CSV file download with Content-Disposition header

Architecture

Component Structure

• page.tsx: Main page composition, manages active tool state
• Toolbox.tsx: Sidebar with tool buttons and export functionality
• FileUpload.tsx: CSV upload component with status messages
• CandleChart.tsx: Core chart wrapper with lightweight-charts integration
  • Initializes chart with dark theme
  • Handles marker annotations (Break Up/Down)
  • Manages click events for annotation creation
  • Exposes refreshData() method for parent updates
• SvgOverlay.tsx: Transparent SVG layer for line drawing
  • Coordinate transformation between data and pixels
  • Two-click line drawing with preview
  • Line hit detection for deletion

Data Flow

1. User uploads CSV → POST /api/upload → SQLite storage
2. Chart mounts → GET /api/candles + GET /api/annotations → Render
3. User clicks with active tool → POST /api/annotations → Refresh chart
4. User deletes → DELETE /api/annotations/[id] → Refresh chart
5. User exports → GET /api/export → CSV download

Development

Project Structure

candle_annotator/
├── src/
│   ├── app/
│   │   ├── api/              # API route handlers
│   │   │   ├── upload/
│   │   │   ├── candles/
│   │   │   ├── annotations/
│   │   │   └── export/
│   │   ├── globals.css       # Tailwind styles
│   │   ├── layout.tsx        # Root layout with dark theme
│   │   └── page.tsx          # Main page
│   ├── components/
│   │   ├── ui/               # shadcn/ui components
│   │   ├── CandleChart.tsx
│   │   ├── SvgOverlay.tsx
│   │   ├── Toolbox.tsx
│   │   └── FileUpload.tsx
│   └── lib/
│       ├── db/
│       │   ├── index.ts      # Drizzle client
│       │   ├── schema.ts     # Table definitions
│       │   └── migrate.ts    # Migration runner
│       └── utils.ts          # Utility functions
├── data/                     # SQLite database directory
├── drizzle/                  # Migration files
├── DEPLOYMENT.md             # Deployment instructions
└── README.md                 # This file

Key Technical Decisions

1. lightweight-charts v4: Stable API with good candlestick and marker support
2. SQLite with better-sqlite3: Synchronous access, perfect for single-user local apps
3. SVG Overlay for Lines: Maintains separate rendering layer from chart, easier coordinate management
4. Drizzle ORM: Type-safe queries with minimal overhead
5. Next.js App Router: Server-side API routes co-located with frontend code

Known Limitations

• Single User: No authentication or concurrent access support
• No Undo: Can only delete annotations, not undo placement
• Memory: Large CSV files (100k+ rows) may cause slow uploads
• Line Snapping: Lines don't snap to candles, free-form placement only

Troubleshooting

See DEPLOYMENT.md for detailed troubleshooting steps.

Common issues:

• better-sqlite3 binding errors: Run npm rebuild better-sqlite3
• Port 3000 in use: Use PORT=3001 npm run dev
• Database corruption: Delete data/candles.db and restart

License

ISC

Contributing

This is a focused tool for a specific use case. For questions or issues, please open a GitHub issue.