After launching FlexiTrace use the OPEN... option under the FILE menu to open your scanned image or one of the sample images that accompany FlexiTrace. This opens a FlexiTrace window showing the image to be digitized.
Next you might want to use FlexiTrace's "plumb-bob" tool to vertically align your image (more on this later) and one or more of FlexiTrace's other tools to clean up stray marks (dirt) on the image (more on cleaning images below as well).
When you think the image looks right, use the FlexiTrace "dimensioning" tool to drag a box across the portion of the image to be digitized. This operation is similar to using a Marquee Tool in paint programs.
The "dimensioning" tool icon is not intuitive to me, but it might be more visible and apparent on a larger screen. The icon shows a two headed arrow spanning two parallel lines, i.e. a typical dimensioning symbol in drafting. My main problems with this icon are its small size and the fact that dimensioning does not necessarily connote selecting the region to be digitized.
Do not include the x and y axes in the portion of the image to be digitized, or else you will digitize them as well, which is undesirable.
After selecting the portion of the image to be digitized with the "dimensioning" tool, a dialog box appears into which you enter the minimum and maximum values of the ordinate and abscissa (x and y axes).
Before performing the digitization, called "tracing" and hence the name FlexiTrace, you will probably want to change some of the default tracing parameters. There are three logical groupings of these parameters: Tracing, Filtering, and Output. The user can easily switch among these three related sets of parameters using FlexiTrace's unique "Trace Parameter Polylog" window, a kind of multi-function window that uses a horizontal shuttering effect to switch among the three related windows.
Tracing Options include type of graph (line, area, bar, scatter), sampling method (along ordinate or abscissa), number of samples, and display options for indicating the sampled points on the graph.
Filtering Options include a "Grid" filter for removing background x-y grid lines that may have been on your original x-y plot and a "Spike" filter for eliminating narrow spikes that are common in experimental data. A third filtering option, "Noise" is also available, though not in the same menu for some reason. The noise filter can be used in multiple passes to eliminate isolated groups of stray pixels; each application of the noise filter looks for groups of pixels with one more additional neighboring pixel, i.e. one neighbor, two neighbors.... (I have also used the noise filter to clean up other scanned images and dirty faxes that arrive via my fax modem; a very handy tool.)
Output options include mode of exporting/displaying the digitized data (text file, FlexiTrace's "Measurement Window," or the clipboard) and an option for selecting the number of decimal places in the x and y data. All exported data is tab delimited.
Now you simply click on "Trace" and your scanned image is automatically turned into the desired digital data.
If you are not happy with the result you can repeat the above procedure, or parts of it. There are nice (easy) ways of reverting back if you do not like your choices.