Help with WebPlot Digitizer

Background

From time to time we need to extract data from images. Today, we mostly work from digital images, but the principles date back to photography. For example, you may need to measure the length of a shell. In general, if a known unit of measure is included in the image, then a calibration can be obtained between number of pixels and units of measurement (mm, cm, etc.). Lengths on uncalibrated images are recorded as number of pixels.

This post is not about how to acquire good quality images suitable for “science,” but instead briefly introduces you to free software that can be used to extract data from images with WebPlotDigitizer, an online tool to help extract data from plot images.

While I prefer imageJ, WebPlotDigitizer is useful for 2D images. Below, an instructional video.

link to instructions: SOP_WebPlotDigitizer_lines