# How to scan diagrams with Engauge

“The Engauge Digitizer tool accepts image files (like PNG, JPEG and TIFF) containing graphs, and recovers the data points from those graphs.” Source

### Step by step guide:

1. Go to File -> Import to import a file or run engauge <Name-Of-The-File> from the command line.

2. From the Background Toolbar (top left) change the option from Filtered image to Original image.

3. Depending on how many curves you wish to digitize from the graph, go to Settings -> Curve List…. From there you can add, remove and rename the separate curves.
The names of the curves should correspond to the names of the actual curves drawn.

4. The way the curves are formed ( connected from one point to another) varies and can be smooth, which is the default, or straight.
To change that go to Settings -> Curve Properties... -> Connect as and choose Function - Straight.

5. Select the Axis Point Tool from the toolbar. You need to set 3 axis points.

1. The first one will be the start of the graph (bottom left corner) which usually corresponds to (0,0), but not always.

2. The second point should on the X-axis line, but not too close to the first point (0,0) because of the error introduced by hand pointing can affect the results. It should be as far away so the error does not matter that much.

3. The third and last point will be on the Y-axis. Again it should follow the same guidelines as the second point.

6. To start digitizing a curve select Curve Point Tool from the toolbar, select the curve from the Currently selected curve zoom in and start clicking on top of the curve from the start until the end. If you have to do it for more than one curves, change the curve selection and repeat. Also, the settings of step 4 have to be repeated for each line if needed.

After the completion, save the file by going to File -> Save… and if you wish to export it as a CSV file go to File -> Export…. Choose a name that provides information about the graph.