 Engauge Digitizer - Digitizing Line Graphs
  Engauge Digitizer - Digitizing Line Graphs
Typical Set of Steps To Digitize Line Graphs
The following steps digitize a linear cartesian graph with 
one curve:
- Obtain an image file (bitmap, jpeg or other) showing one or more 
curves 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 Segment Fill button to automatically digitize entire curve
segments at a time.
- Click on a segment underneath the cursor to fill that segment
with a set of curve points. Repeat until the segments have
been digitized.
- Click on the Curve Points button to manually enter curve points.
- Click on the curve to add a curve point. Repeat 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/Background/Show Filtered 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