Notes for digitization of figures with Matlab:

Using function digitization.

Download digitization.m to your work space.  Help can be found in the pdf document Digitization.pdf

1. For a jpg image:  load in the file with  A = imread(‘filename.jpg’);

2. Place the image in a figure window:  Image (A)

3. [data,calib] = digitization([calibin])  (no input on first call. The calib structure can be used later on.

4. Follow the instructions to identify x0,x1,y0,y1 by pointing to them.

5. Returns one array and one struct: data and calib.  Calib can be used in further digitizations

6. data has the x,y data points in two columns.

Using the script digitize

Download digitize.m to your work space.  Help can be found by entering the command help digitize at the command line, when the working directory includes the m-file.

1. Execute script digitize.m

2. Under load menu, select load image, and click on filename.jpg

3. Enter Transformation menu and select Add Points. 

4. Left click on the reference pts; right click when done

5. Right click on each reference point to add true coordinates

6. To digitize: enter the digitization menu and select add points

7. When finished with points, enter Export menu and select digitized points to workspace.

8. The (x,y) cords will show up in xd and yd.

Using engauge digitzer

This is a nice digitizer (shareware), but it creates a data file outside matlab that must be imported.

Download and install engauge.

1. Launch the application engauge.

2. Under the file menu, select import and load in the *.jpg file.

3. Using the axis icon (axis only) specify the three points needed for the x,y axis.

4. Under digitize use curve point and select the points to be digitized.

5. Under settings make sure that the export format is comma delimited.

6. Under file select export as and save the file as a *.dat file.

7. Import the data into matlab by opening Matlab and selecting file>import data and then letting the import wizard guide you.

8. The x,y data will be in two columns of the data array.