How to extract data from a graph image

You have a graph and you need the numbers behind it. Here is the quick way, and how to make sure the numbers are right.

Drop in a graph or a PDF

Three steps

  1. Get the best copy of the graph you can. A PDF is best. Otherwise take a large, sharp screenshot of the figure alone.
  2. Drop it on the home page. The axes, series names and points are read automatically.
  3. Look at the rings on the chart. Each ring is one value, placed by the axis that was read. Fix any that sit off their mark, then download.

PDF or picture?

When a PDF holds the chart as a drawing (most figures in papers do), the values are read from the drawing itself. Nothing is estimated from pixels, so a point is as precise as the file is.

A picture (a screenshot, a scan, a PNG or JPEG) is read by an AI model. Every value is then drawn back on the picture as a ring, so a wrong one is easy to see and to correct in the table.

What can go wrong

Small, crowded figures are the hard case for pictures: when a plot is only a couple of hundred pixels high, a pixel is already a visible error. Use the PDF when you have it, or a larger screenshot.

Lines that cross many times in the same colour, and markers hidden under other markers, are the usual cause of a missed point. The chart view shows them at once.

Questions

How accurate is it?

From PDFs, values are read from the drawing and are exact. From pictures of charts we drew ourselves, 280 of 300 came out fully right; figures from published papers are harder, which is why every value is shown for checking.

Can it read a log axis?

Yes, and date axes and charts with a second y axis.

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