peterstangl / svg2data

A Python module for reading data from a plot provided as SVG file.

svg2data

A Python module for reading data from a plot provided as SVG file.

• Dependencies
• Installation
• Usage
  • The svg2data class
    • Axes
    • Graphs
    • Generating a simplified SVG file
    • Plotting the extracted data
• Converting a PDF to an SVG file

Dependencies

In addition to the Python standard library, the svg2data module relies on the packages numpy for numerical calculations and matplotlib for plotting and providing font metrics.

Installation

To install the package in your user space, change to the repository folder and enter

pip3 install -e . --user

Usage

The main functionality is provided by the class svg2data. It can be imported with

from svg2data import svg2data

To use the plotting feature inside an IPython notebook, you may execute the following line inside the notebook:

%matplotlib inline

The svg2data class

The class svg2data is used to read data from a SVG file containing a plot. This is done by creating an instance of the svg2data class with the path to the SVG file provided in the argument:

data = svg2data("/path/to/file.svg")

Axes

All information on the axes of the plot are contained in a list of dictionaries and can be accessed by

axes = data.axes

Graphs

All information on graphs in the plot are contained in a list of dictionaries and can be accessed by

graphs = data.graphs

Generating a simplified SVG file

When processing the input SVG file, all contained coordinate transformations are performed on the path elements (W3C provides detailed information on coordinate transformations and path elements in SVG files). A new SVG file with all transformations on paths already performed (and some further simplifications) can be written to disk using the writesvg method:

data.writesvg('/path/to/newfile.svg')

This is in particular useful for verifying that all transformations were performed properly.

Plotting the extracted data

To check if the extraction of the data from the original SVG file was succesfull, the plot method can be used:

data.plot()

This will produce a plot from the extracted data.

Converting a PDF to an SVG file

Since many plots are only available as a PDF file, one has to convert them to SVG for extracting data using svg2data. For this purpose, one can use Inkscape from the command line:

inkscape --without-gui --file=input.pdf --export-plain-svg=output.svg

SVG files created by pdf2svg are not supported since this tool converts text to paths and thus prevents automatic extraction of the scales of the axes.