A DataThief alternative for today's browsers
DataThief is a desktop program that needs Java and has you place the axis points and trace the line yourself. Chart to Data needs only a browser and reads the chart automatically.
What changes
- No Java, no install.
- The axes are read from the chart's own numbers.
- Scatter points, bars and error bars are read as well as lines.
Precision
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.
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.
Questions
Can it read a scanned graph?
Yes. A scan is read as a picture, and a page that was scanned slightly crooked is straightened first. Check the rings on the chart before you use the numbers.