Engauge Digitizer - Digitizing Graphs

Complete Set of Steps To Digitize An Image File

The following steps manually digitize a linear cartesian graph with one curve:

Obtain an image file (bitmap, jpeg or other) showing one or more graphs and both axes
Import the image file using the File/Import menu option
Click on the Axes Point button before entering axes points. These will define the coordinate system
Click on one of the axes to add the first axes point, then enter its graph coordinates
Click on one of the axes to add the second axes point, then enter its graph coordinates
Click on one of the axes to add the third axes point, then enter its graph coordinates
Click on the Curve Points button before entering curve points. These will contain the digitized curve data
Click on the curve to add a curve point
Repeat the previous step until the curve is covered with a sufficient number of curve points
Export the curve points into a tabular text file using the File/Export menu option

For speed, the graph can be automatically digitized, rather than manually digitized, as follows:

Click on the Segment Fill button before digitizing entire segments with one click
Click on a curve segment to automatically fill up the segment with curve points

For a graph that is logarithmic or polar:

For a graph with more than one curve:

Select the Settings/Curves menu option to bring up the curves window
Click on the New button to create a new curve, then enter the name of the new curve
Repeat the previous step until all desired curve names have been entered
In the main window, use the Curves combobox to select a curve. While that curve is selected, all new curve points will be assigned to that curve