Content-type: text/html Graph Redigitizer Java 1.1 compatible browser (such as Netscape 4.06 or later) required for this demo.

Graph Redigitizer



This program helps you to read the coordinates of data points from a linear or logscaled graph. The axes of the graph can be non-horizontal, non-vertical, non-perpendicular. The input is a GIF file, the output is a two-column table containing the coordinates marked by you.
Especially useful if you are a theoretical particle physicist and you need the experimental data which the experimental physicists publicized only in some graphical form (as always).

This is free software, see the GPL for details.


  1. Make a GIF file from your graph.*
  2. Load the GIF into the applet (application).
  3. Choose three calibration points (1. origin, 2. a point on the X axis, 3. a point on the Y axis).
  4. Set the real X, Y coordinates of the calibration points.
  5. Mark the data points.
  6. Click the Show button to see the coordinates.
  7. To save the data table: copy it into a text editor with the mouse (in the applet)** or select File/Save (in the application)
If you are a beginner, skip the first three steps and try the demo.

The program can be used not just as an applet but also as an application. Download it if you want to use it on your own machine.

* If the graph is in a Postscript file, view it with ghostview or gv (or any Postscript viewer you like), grab the graph with xv, and then save the grabbed image in GIF format (from xv).

** The applet has no File menu because applets from the web are not allowed to access files on your winchester (except the signed ones, but sign is money).

Downloading and Installation

To use Graph Redigitizer as an application, you need Java 1.3 or later.
  1. Download grdig-0.6.tar.gz.
  2. Extract its contents in your home directory: do
    gunzip < grdig-0.6.tar.gz | tar xvf -
    in unix, or the equivalent in windows.
  3. Edit the grdig/bin/grdig shell script (in unix) or the grdig\dos\grdig.bat batch file (in windows) and copy it into a directory which is in your PATH.
  4. Now you can run the program by typing grdig or grdig file.gif
The program can also be downloaded as an RPM package (for RedHat-based linuxes):

© 1998-2000 Peter Csizmadia