Description
Plot Digitizer is a Java program used to digitize scanned plots of
functional data. Often data is found presented in reports and references as
functional X-Y type scatter or line plots. In order to use this data, it must
somehow be digitized. This program will allow you to take a scanned image of
a plot (in GIF, JPEG, or PNG format) and quickly digitize values off the plot
just by clicking the mouse on each data point. The numbers can then be saved
to a text file and used where ever you need them. Plot Digitizer works with
both linear and logarithmic axis scales. Besides digitizing points off
of data plots, this program can be used to digitize other types of scanned
data (such as scaled drawings or orthographic photos).
To make the digitizing task easier, this program includes
many handy features. For example: You can recalibrate the Y axis
without having to recalibrate the X axis (multiple sets of data are
commonly plotted with the same X axis). You can insert points
between two already digitized points by right clicking and choosing
"Insert" from the pop-up menu. You can delete points by
right-clicking on the points and choosing "Delete". You can move
points by clicking and dragging them. You can compute the length of
a digitized curve and you can compute the area of a digitized
polygon. You can zoom images in and out. You can save calibrations
for an image for later use, and finally, there is unlimited
undo/redo.
A special feature of this program is the ability to
semi-automatically digitize lines off a plot. The user simply
indicates where the line is on the plot with a thick paint brush and
the program attempts to automatically sort out the data from grid
lines, etc. This auto-digitizing feature depends on an image
vectorization program called "autotrace". In order to use the
auto-digitizing feature, you must have the open source autotrace image
vectorization program installed. Unfortunately, autotrace does not
currently seem to work on the Windows platform.
Will the auto-digitizing feature digitize any plot? Short answer:
no. Long answer: The auto-digitizing feature works best with black
and white, 300 dpi images of continuous data which does not run
vertically (vertical lines give it fits), does not repeatedly cross
other data lines, is not close to and parallel to grid lines, is not
extremely noisy and which does not have plot symbols. After using
the program a while you begin to learn what it can and can't
auto-digitize. However, even in cases where it doesn't auto-digitize
the entire line, you can sometimes do a piece of it automatically,
then manually digitize a piece, and then do another piece
automatically, etc. I've found this feature to be pretty useful on
digitizing plots of experimental test time histories, but your
mileage may vary.
This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public
License as published by the Free Software Foundation; either version 2 of
the License, or (at your option) any later version.