Graph Digitzer

Digitizer enables you to digitize a scanned or downloaded linear graph, with a set accuracy.
Updated 18 Feb 2011

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Digitizer is a GUI that enables you to digitize a scanned or downloaded linear graph. The output is stored as an ascii file.

Step 1 - Load image
Loads any image that can be handled by the imread command.

Step 2 - Calibrate the image:
While calibrating, the menus are enabled.
You can choose a maximum of 2 points on the graph.
The arrow keys on the keyboard will move the last entered point with small steps to accurately place your calibration points.
The input is cyclic for two points i.e. the third input will replace the first input etc.
To finish input press the 2nd mouse button, after which the numeric values of the chosen two points can be entered.
You can calibrate or recalibrate at any time when you are not using the input feature.

Step 3 - Start Input
During input, all menus will be disabled:
Mouse button 1: Add a new point
Mouse button 3: Removes the last point (only if you have three mouse buttons, button 3 is the center one)
Mouse button 2: Ends input
As long as the graph is not resetted, you can start and stop input at will, for example to change the accuracy or to recalibrate.

Input accuracy: The input will snap to the rounded value as specified in the preferences.
During input, arrow keys will move the last point in steps according to the scale of the graph as defined in the preferences.

Step 4: Save data
The digitized data is stored in an ascii "Graphfilename.txt"

Example of output:

The digitzer REQUIRES round2 from with input
round2(value,decimal places) as provided here at the file exchange as File ID: #4261.

Cite As

S. A. van der Wulp (2024). Graph Digitzer (, MATLAB Central File Exchange. Retrieved .

MATLAB Release Compatibility
Created with R2008a
Compatible with any release
Platform Compatibility
Windows macOS Linux
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Version Published Release Notes

Update Feb 18th 2011 :
Replaced imshow for image command
GUI will ask to check preferences after image calibration

updated help function

Help function problem solved

Added an example

Made a few corrections that enhances user friendlyness.