An AI-Powered K-Line Chart Analyzer — Upload a Screenshot, Get Structured Technical Analysis

yuan chen — Thu, 23 Apr 2026 07:19:56 +0000

The Problem

Every trader has been here: you're staring at a candlestick chart, trying to figure out if that's a Head and Shoulders forming or just noise. You flip between three indicator panels, check RSI, squint at the MACD histogram, and still aren't sure.

I wanted a tool where I could just screenshot a chart and get a structured breakdown — patterns detected, trend direction, confidence scores, and what to watch next. No manual drawing, no subjective interpretation.

So I built KlineVision.

What It Does

Upload any K-line (candlestick) chart screenshot — A-shares, US stocks, crypto, anything — and KlineVision returns:

Classic Pattern Detection — Head & Shoulders, Bullish Engulfing, Morning Star, Flags, Triangles, and 70+ more patterns with confidence scores
Chan Theory Analysis (缠论) — Bi (笔), Duan (线段), Zhongshu (中枢), and Beichi (背驰) structure detection. If you trade Chinese markets, you know how powerful this is
Trend Judgment — Bullish / Bearish / Sideways with strength and confidence
Trading Signals — Contextual buy/sell/watch signals with risk notes
Bilingual Output — Full analysis in both English and Chinese

The analysis is powered by Google Gemini's vision model with a carefully crafted prompt that enforces structured JSON output.

The Tech Stack

Next.js 16 (App Router, TypeScript)
├── EODHD + Tushare (market data)
├── Supabase (auth + PostgreSQL)
├── Stripe (subscriptions)
├── SVG K-line renderer (server-side, zero deps)
└── 11-locale i18n (en/zh/ja/ko/es/fr/de/pt/ru/ar/hi)

A few things I'm proud of:

Pure SVG K-Line Renderer

Server-rendered candlestick charts that crawlers can see (no Canvas/WebGL). I wrote a pure TypeScript SVG string generator — zero native dependencies, works in Vercel Serverless. It draws candlesticks, MA lines, volume bars, pattern highlights, and annotations, all as SVG XML strings.

Each page has real data — historical win rates, T+5/10/20 return statistics, recent detection cases — not LLM-generated fluff. The pattern detection runs a rule-based engine on actual OHLCV data from EODHD and Tushare.

11-Language Support

Every page renders in 11 languages with proper hreflang tags. Entity content (pattern names, descriptions, FAQs) is stored as L10n objects:

name:
  en: "Bullish Engulfing"
  zh: "看涨吞没"
  ja: "強気の包み足"
  ko: "상승 장악형"
  # ...

Translation is done via Gemini batch API (~$0.15 for all entities × 9 languages).

The prompt is the secret sauce — it forces Gemini to output a strict JSON schema with confidence scores, bilingual explanations, and explicit "what I can't determine from this image" sections. No hallucinated price targets.

Pattern Detection Pipeline

Beyond the screenshot analysis, there's a daily data pipeline:

Fetch — Pull OHLCV data from EODHD (US/A-shares) and Tushare (HK)
Detect — Rule-based engine scans for 10 candlestick patterns (Hammer, Engulfing, Doji, Morning/Evening Star, etc.)
Backfill — Calculate T+5/10/20 returns for historical detections
Compute — MACD, RSI, Bollinger Bands snapshots for each stock
Aggregate — Win rate statistics at global/market/symbol level

Try It

Upload a chart: klinevision.ai
Browse patterns: klinevision.ai/patterns
Check a stock: klinevision.ai/stocks/us/AAPL
Scan for patterns: klinevision.ai/scanner/doji/us

The core analysis feature is free. I'd love feedback from anyone who trades or is interested in technical analysis.

What's Next

More chart patterns in the rule engine (currently 10, targeting 30+)
Multi-timeframe confirmation (daily + 4h + 1h)
Real-time pattern alerts via Telegram
Hong Kong market expansion (Tushare rate limits are... fun)

DEV Community: yuan chen