About Graph Detector
Graph Detector is a free, browser-based tool that converts graph and chart images into precise numerical data you can actually use. Whether you are looking at a scanned journal article, a screenshot from a presentation, or a photograph of a whiteboard plot, Graph Detector lets you click directly on the curve, calibrate your axes, and download a clean CSV file — all without installing any software or creating an account.
It is trusted by researchers, engineers, students, and analysts across more than a dozen fields to recover data from images where the original dataset is unavailable.
Key Features
Interactive Axis Calibration
Click directly on the graph's origin and maximum corners to set the real-world coordinate scale. Supports both linear and logarithmic axes on X and Y independently. The calibration box is draggable for fine-tuning.
Click-to-Place Data Points
Switch to Add Point mode and click anywhere on the canvas to mark data points in exact order. Points connect in the order they are placed — no automatic sorting that scrambles curved or non-monotonic data.
Drag-to-Adjust Editing
Switch to Edit Points mode and drag any individual point to refine its position. Full Ctrl+Z / Ctrl+Y undo and redo history is maintained across all editing actions.
Multi-Curve Support
Add as many curves as your graph contains. Each curve has its own colour (changeable via a built-in colour picker), custom label, and independent point set. Press [ / ] to switch between curves from the keyboard.
Calibration Memory
Your last calibration is saved locally in the browser. When you upload a new image of the same graph type, you can restore the previous calibration instantly — no need to re-enter axis values from scratch.
Smart CSV Export
Export all curves in one structured CSV. The file name automatically includes your original image name and today's date, making it easy to manage multiple exports. Adjust the number of interpolated points per curve before downloading.
Zoom, Pan & Fit
Scroll to zoom in on dense regions, use Pan mode to navigate, and click ⊡ Fit in the toolbar to instantly reset the view to show the full image.
Wide Format Support
Accepts JPG, JPEG, PNG, WebP, BMP, and TIFF images — covering scanned documents, screenshots, photographs, and exported figures from virtually any software.
How It Works
Graph Detector uses a canvas-based interactive workflow:
- Upload — your image is sent to the server where it is stored temporarily during your session. It is never shared, sold, or stored permanently.
- Calibrate — you click two reference points on the canvas (the plot origin and the maximum corner) and enter their real-world axis values. Graph Detector computes the pixel-to-coordinate mapping and draws the calibration box on screen.
- Digitize — you add curves and click along each curve in the image to place data points. The canvas shows your points connected in placement order with live coordinate feedback as you move the mouse.
- Export — Graph Detector interpolates your points and writes them to a CSV file. Real-world X/Y values are calculated using your calibration, including correct handling of logarithmic scales.
Who Should Use Graph Detector
Graph Detector is built for anyone who needs to work with data that is locked inside an image:
🔬 Researchers & Scientists
Re-digitize experimental results from published papers when raw datasets are unavailable for meta-analysis or comparison.
⚙️ Engineers
Extract material property curves, Bode plots, and performance charts from equipment datasheets to feed simulation models.
🎓 Students & Educators
Pull data from textbook figures to run independent analyses or verify published results in coursework and research projects.
💊 Medical Professionals
Digitize pharmacokinetic profiles, dose-response curves, and clinical trial graphs from literature for further statistical work.
💹 Financial Analysts
Extract trend lines and data series from infographics, reports, and historical financial charts to build quantitative models.
🌍 Anyone with a Graph Image
If you have a chart and need the numbers behind it, Graph Detector can help — regardless of the field or the source of the image.
Why Choose Graph Detector
- Completely free — no subscription, no credits, no hidden limits. Use it as often as you need.
- No installation — runs entirely in your browser. Works on Windows, macOS, Linux, and modern tablets. Nothing to download or update.
- Fast workflow — from image upload to CSV download in under two minutes for a typical single-curve graph.
- High accuracy — you place points yourself rather than relying on automated detection, giving you full control over the precision of the output.
- Log-scale ready — one of the few free tools that correctly handles logarithmic axes on both X and Y, essential for scientific and engineering data.
- Safe to experiment — unlimited undo/redo and a 5-second curve-deletion undo window mean you can work without fear of losing your progress.
Technology Stack
- Backend: Python with Flask; OpenCV and NumPy for image processing; Pillow for multi-format image support
- Frontend: Vanilla JavaScript (no frameworks) with an HTML5 Canvas for all interactive drawing, zoom, and pan
- Coordinate engine: Custom pixel-to-real-world mapping with full support for linear and logarithmic axes
- Storage: Images are held in a temporary session directory and are not stored permanently
- Deployment: Hosted on Vercel for global low-latency access
Frequently Asked Questions
Is Graph Detector free to use?
Yes — completely free. No account, subscription, or credit card is ever required.
Do I need to install any software?
No. Graph Detector runs entirely in your web browser. It works on any modern desktop, laptop, or tablet — no downloads, no plugins.
What image formats are supported?
JPG, JPEG, PNG, WebP, BMP, and TIFF. If your image is in a different format, convert it to PNG first using any free image converter.
Can I extract data from graphs with logarithmic axes?
Yes. During calibration you can set X Scale and Y Scale to Log independently. Graph Detector then applies the correct logarithmic mapping when computing real-world coordinates.
How accurate is the extracted data?
Accuracy depends on image resolution and calibration precision. With a high-resolution image and careful calibration, coordinates typically match the original data to within 1–2 % of the axis range. Zooming in on the canvas before placing points improves accuracy further.
Can I work with graphs that have multiple curves?
Yes. You can add as many curves as your graph contains, each with its own colour and label. All curves are exported together in a single CSV file with separate X/Y columns per curve. Use the [ / ] keys to switch between curves quickly.
Is my uploaded image kept private?
Images are uploaded to a temporary session directory on the server for processing during your session. They are not stored permanently, not shared with third parties, and not used for any purpose other than generating your CSV export.
What happens if I accidentally delete a curve?
Curve deletion has a 5-second undo window. A toast message appears immediately after deletion — press Ctrl+Z within 5 seconds to fully restore the curve and all its points.