Using AutoScan

       When the AutoScan Record button is clicked, a special 
         screen-capture is performed and a new image is displayed in a window over the current screen.  In this capture, all the pixels that lay within a rectangular region defined by your axis dialog clicks are grabbed and redisplayed in a new window that AutoScan uses.  The AutoScan Record picture below appears near the captured image.

      The Add, Play, and Stop buttons perform the same functions as 
        those described for the Mouse Record mode.

       The Pencil, Lasso, and Eraser tools work just like those in painting 
         programs.  In general, you will use the eraser tool to "clean up" an        
         image to be autoscanned, the pencil to edit the pixels in a  curve, and 
         the lasso to select a portion of the image to be scanned.

        The eraser tool has four different sizes — use Click, 
         Option-Click, Command-Option-Click, and Command-Click, 
         respectively, while clicking on the eraser tool button to switch 
         between the various eraser sizes shown.

     With digiMatic , cleaning up an image does not mean you must erase every stray pixel in the image.  You need only erase as much as necessary to lasso a given part of the image to be scanned without having extraneous pixels within the selected region.  Generally, it is best to do basic cleanup (e.g., remove parts of the axes that might interfere) first and then click the Save button in the AutoScan Record window.  This stores the displayed image with any cleanup you have done as the "current" image. 
      Subsequently, you may erase more of the image in order (for example) to scan a section of a curve.  Often, the portion you erase will be of interest to scan as another curve.  After selecting and scanning the first portion, click the Revert button to restore the previously saved image.  Your initial cleanup work is still intact and you won't have to begin the process entirely from scratch.

               The Scan button begins the screen-scan.  The AutoScan 
                 Record box will modify itself to show scanning progress and the number of data points recorded.  You may AutoScan any portion of an image, click the Stop button, and then use the Mouse Record mode to add more points manually or to add a second curve.  You can mix and match the modes however you like.  Mixing digitizing modes is especially important for getting optimum results.  The reasons for this will become clear as we discuss how AutoScan does its job.
      In an AutoScan session, you can automatically "screen-scan" selected portions of a curve and

      1)  record as a point the value at each and every black pixel within 
           the selected region, or
      2)  record as a point only the value at the first black pixel encountered 
           in the scan "direction", or
      3)  record as a point the average of the values for all the black pixels 
           in a scan "direction" within the selected region.

      Now, since that last sentence reads like the blurb from the IRS in the Foreword, allow us to explain what on earth all that means...

      In the Options box, suppose you have selected the option to scan in the "Y direction" by moving across a selected region in the X 
       direction (i.e., you clicked the Y-direction button in the Options 
          box).  This option is most useful for curves which are relatively 
parallel to the X axis.  When AutoScan is started, digiMatic  goes to an  X location at the lower left of an invisible rectangular area which encompasses a selected region.

      Starting from the lower left corner of the rectangle, digiMatic  scans vertically (in the "Y direction").  If Point Averaging is off in the Options box, digiMatic  records as a data point the first black pixel it encounters within the selected region as it scans upwards and then moves immediately to the next X pixel location.  If you have a curve image that is a particularly fat line, you may wish to turn Point Averaging on.  In this case, digiMatic  will continue to collect all black pixels on a given X pixel vertical within the selected region and then average the Y values it finds and records a single average Y value at the X location.

        When this AutoScan option in set in the Options box, scanning 
          functions analogous to those above are used.  In this case, scanning occurs in the "X direction" while moving vertically within the invisible bounding rectangle.  This mode is useful for curves that are relatively 
parallel to the Y axis.

         When this AutoScan option is set in the Options box, values at all        
           black pixels (meaning every one, each and every, inclusive, all of them) are recorded as data points.  You might guess that having Point Averaging turned on with this option makes little sense — however, we left this option available just in case you think of some reason for using whatever weird average this might return.  Be aware that using this option to scan a selected image with lots and lots of black pixels will quickly tally up thousands of recorded values.  Your limit for recorded values on a single curve is 1500 and 5000 for any one session.  If you overrun the 1500 point/curve limit, an alert box will pop up and complain.  When this happens,  try adding another curve and lassoing the remaining portion of the curve to capture the missed points.

Scanning Peaks
       Suppose you have a scanned image from a chromatogram or like the infrared spectrum of poly(methyl methacrylate) below.  You may know this material by the name Plexiglas.

      If you attempt to AutoScan the vertical sections of the peaks using Y-direction scanning, your results will likely be less than satisfactory.  While the portions of the curve that are relatively parallel to the X Axis can be autoscanned with good results, the peaks are a problem since the vertical nature of the curve will result in either (1) too low a Y value at a given X being obtained if Point Averaging is off or (2) too low a Y value being obtained at the peak if Point Averaging is on.
      In the first case, the value recorded is the first pixel encountered in the vertical scan.  Since scanning of this image at 72 dpi resulted in loss of separation definition at the peak, the first pixel encountered will be well below the peak value.  With Point Averaging on, you will get all the pixels at the peak X value, but the average will still be too low.
       One option is to use Y-direction scanning to digitize the relatively flat portions of the curve, then switch to X-direction scanning to digitize the peaks.  If you do this, you will have to select each side of each peak individually for scanning.  Not difficult at all, but it could be somewhat time consuming.  Another option might be to use Y-direction scanning for the horizontal sections and then switch to Mouse mode to digitize values along the peaks.  We will illustrate this technique in the Tutorials chapter later in the manual using the spectrum above.  A third option is to place the image in a painting program and then use FatBits to edit the image so that a single pixel occurs on each X pixel vertical.  Then, digiMatic  can AutoScan the entire curve.  How accurately you reproduce the original spectrum will depend on how well you edit the image.  In most cases, edit the bitmap to leave just those pixels along the top of the curve.
      There are still some things that humans can do better than computers.  One of these is deciding whether a pixel is a point and not just another dot.  The best image analysis software on earth is no better than your own eye-brain combination at picking off peak points from a digitized image like the one above.  We have taken the approach that screen scanning is useful for some digitizing jobs, but we decided to rely on the user in situations where image analysis algorithms can't be counted on in every situation that might arise.  Thus, we have not included slow and painful scanning analyses to try to judge whether or not a peak is a peak.  You can do this very, very quickly with a few point and click records in Mouse mode.  Learn to use both Mouse and AutoScan together and you'll quickly get great results.

Where To Go From Here
      Before going on to the Tutorials, you will want to understand all of the functions offered in the Editor.  Choose Using The Editor from the Table of Contents.