For the polygon match tracelines are defined, perpendicular to the polygon. Edges found along these tracelines are then used to find the optimal polygon match.

Note: similar settings are also available per traceline on the Setup/Polygons tab - the MultiSearch mode on the Polygon match can also change the traceline settings

Tracelines

• Use trace line count - specify number of tracelines per polygon

• N - Count - number of trace lines

• L - Step length (pixels) - compute trace line count by placing the lines apart by this distance

• s - Start point (pixels) - distance from polygon

• e - End point (pixels) - distance from polygon

• l - Trace step (pixels) - sample distance

• w - Line width (pixels) - how many extra trace lines on each side (at distance 1 pixel)

• Use pixel size from original image (not resampled) -

  • when selected, the traceline settings refer to the pixels in the main (original) image.

  • Otherwise the resampled pixel size will be used.

Edge detection

• b - Smooth base - filter length

• m - Smooth counter - filter repetitions

• d - Differentiation - number of times to differentiate samples

• H - Percent threshold

  • If unchecked, the threshold used is the fixed one in the Threshold edit field.

  • If checked, the threshold used for each trace line is computed as a percentage of the current max value, but never below the Min threshold value.

• h - Threshold/Min threshold - see line above

• p - Polarity - which edge to search for

• M - Mode - edge detection

• C - Edge choice - which edge to retain when multiple are found for a trace line

Trace line samples dialog

A graph of sample values for selected tracelines. Only samples from the best match template are shown. Choose which line(s) are shown using

• Middle/Middle+edges/Selection - select tracelines in polygon

• Line indices - traceline selection
  • example: 2,3,12-15
  • example: 1 3 5 7

• Polygon number - select which polygon

• Show trace line popup - display dialog

Traceline sample dialog