PLOTTRACE
PLOTTRACE turns any graph image — a scanned chart from a textbook, a research paper figure, or a photo of a printed plot — into exact numeric data. Upload the image, tell it what your axes mean, then click along the curve to capture data points, which you can export as a clean CSV file.
Drag-and-drop or browse for a PNG or JPG of the chart you want to digitize.
Mark two known reference points on each axis so pixel positions convert to real values — supports linear or logarithmic scales.
A built-in magnifier helps you click precisely on the curve; every click is instantly converted to X/Y data.
Zoom, pan, undo the last point, or clear everything and start over — nothing is destructive until you export.
Extracted points are sorted by X and ready to download as a CSV, or copy them straight into a spreadsheet.
Switch to a distraction-free full-screen canvas for detailed, careful tracing work.
Upload your graph image
Click Open Image in the top bar (or the upload icon in the left tool rail) and choose a PNG or JPG of the chart. You can also drag the image straight onto the canvas.
Calibrate the X axis
Select the Calibrate X axis tool, then click two points on the image whose real X values you already know (for example, the axis's 0 and 10 marks). A small popup asks you to type the actual value for each point. Turn on LOG next to the axis if it's a logarithmic scale.
Calibrate the Y axis
Switch to the Calibrate Y axis tool and repeat the same process vertically — click two points with known Y values and enter them in the popup. Once both axes are set, the tool can convert any pixel on the image into real coordinates.
Trace the curve
Choose Add data point and click along the curve, from left to right. Each click drops a marker and instantly shows its converted X/Y value in the HUD. Use the built-in magnifier to click precisely, and switch to Pan canvas or scroll to zoom when you need to move around a large image. Made a mistake? Undo removes the last point, and Clear removes them all.
Review and export
Check the growing points table and live preview in the side panel. When you're happy with the trace, click Download CSV to save the file, or Copy as text to paste the values directly into a spreadsheet or report. Points are always exported sorted by X.
| Tool | What it does | |
|---|---|---|
| Open image | Load a new graph image from your device. | |
| Fit to view | Reset zoom and pan so the whole image is visible. | |
| Calibrate X axis | Set two known reference points on the horizontal axis. | |
| Calibrate Y axis | Set two known reference points on the vertical axis. | |
| Add data point | Click along the curve to record data points (enabled once both axes are calibrated). | |
| Pan canvas | Drag to move around a zoomed-in image. | |
| Undo | Remove the most recently placed point. | |
| Clear all | Remove every placed point and start the trace over. |
Pick calibration points far apart. Using two axis points that are close together makes small pixel errors translate into larger value errors.
Use the magnifier. Zoom in before clicking on the curve, especially where it's steep or crosses gridlines.
Log axes. If your original chart uses a logarithmic axis, turn on the LOG toggle for that axis before calibrating — values will convert correctly.
Recalibrate anytime. If a point looks off, you can re-click a calibration point to correct it without losing your traced data.
Go full screen for long traces. Use the full-screen button (top-right) for a larger, distraction-free canvas when digitizing detailed curves.
PLOTTRACE is built and maintained by Vivek Shah, who writes and builds tools for engineers and students under the "My Thoughts" blog and the ervivekshah.com.np brand.
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