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Table 3 Convexity defect measures used for ranking

From: SHERPA: an image segmentation and outline feature extraction tool for diatoms and other objects

Absolute measures

CDF

"Convexity Defection Factor", depicts the percentaged difference between area resp. perimeter of contour and convex hull [53]

PCAF

The "Percent Concave Area Fraction" compares the areas of contour and convex hull [54].

CHMDF

For the "Convex Hull Maximum Distance Factor" each convexity defect’s maximum distance between contour and convex hull is calculated. For distances larger than pixelwidth the squares of the distances are summed up to the CHMDF [53].

Relative measures

CDF-Match

Ratio of CDF of object and template

PCAF-Match

Ratio of PCAF of object and template

Compactness-Match

Ratio of heuristic descriptor "compactness" between object and template shape

  1. Absolute measures result from the object and are judged directly by their values, relative measures result from comparing values between object and best matching template.
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BMC Bioinformatics

ISSN: 1471-2105

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