PlotDigitizer is the best tool for data extraction from graphs, images, and plots. It comes with many useful features.
PlotDigitizer has an inbuilt math parser that eases data extraction. You can quickly extract data points from graph and plot images.
PlotDigitizer is the best free alternative to Engauge Digitizer for data extraction from graph and plot images.
PlotDigitizer is the best free alternative to WebPlotDigitizer for data extraction from graph and chart images.
The best alternative to Datathief, a data extraction tool from graphs, is PlotDigitizer.