Engauge Digitizer - Digitizing Point Graphs

Warning: Not all point graphs work well when automatically matching points in Engauge. Before going any further, you may want to read about point match requirements.

Typical Set of Steps To Digitize Point Graphs

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

Obtain an image file (bitmap, jpeg or other) showing one or more graphs and both axes
Import the image file using one of the following options:
- File/Import menu option
- Copying and pasting
- Dragging and dropping
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 Point Match button to automatically digitize many curve points.
Click on a sample point, and then use the arrow keys to accept or reject points that match the sample point.
Click on the Curve Points button to manually enter curve points.
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 curve points using one of the following options:
- File/Export menu option to save selected curves into a tabular text file
- Copying and pasting to copy points in the current curve from the curve geometry window to another application
- Dragging and dropping to copy points in the current curve from the curve geometry window to another application

Optional Steps

To clean up the image for better performance of Segment Fill and Point Match: steps:

Show the processed image, rather than the original image, by selecting the View/Processed Image menu option
Adjust the discretize settings using the Settings/Discretize menu option, until unwanted parts of the image disappear
Remove grid lines using the Settings/Grid Removal menu option

For a graph that is logarithmic or polar:

Select the Settings/Coords menu option to bring up the coordinates window
Select the appropriate coordinate settings

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