Standard Quality Measures and Associated Signal Transformations

Quality Measures

The desired quality measure is specified in the [quality] section of a configuration file using the object_quality parameter, for example object_quality = bright_on_dark_contrast. The minimum quality value an object must have to be considered acceptable is specified using the min_quality parameter in the same section, for example min_quality = 1 (see Configuration File).

Current standard quality measures are:

contour, bright_on_dark_contrast, dark_on_bright_contrast, bright_on_dark_gradient, dark_on_bright_gradient.

Note

Although quality measures might be described as “Python functions” in the documentation, they are in fact Python classes. The full name of these classes are obtained by suffixing the names used in the documentation by “_t”. For example, bright_on_dark_contrast_t for bright_on_dark_contrast.

The contour quality aggregates the signal along the contour of the object. The supported aggregation functions are: mean, stddev (standard deviation), variance, median, min, and max. The associated parameter is named measure. Its default value is mean.

The contrast-based qualities measure how far apart the average signal value inside the object and the average in its neighborhood are.

The gradient-based qualities measure how aligned the gradient of the signal along the object contour and the contour normal are. The parameters of these quality measures are:

• bright_on_dark_contrast

  • ring_thickness_ext: thickness of the outside ring used to compute object contrast.
  • ring_thickness_int: thickness of the inside ring used to compute object contrast. By default, use full object interior.
  • normalized: set to True or False to choose whether to normalize the contrast by the square root of the product of the standard deviations in the outside and inside rings.

• bright_on_dark_gradient

  • max_hole_size: gradient and normal can be consecutively misaligned for at most this length.

• The dark-on-bright counterparts have the same parameters.

The desired quality parameters are specified in the optional [quality prm] section of a configuration file, for example ring_thickness_ext = 3 (see Configuration File). However, note that all these parameters have default values (which explains why the [quality prm] section is optional).

For details about the respective parameters of the quality measures, see Section Parameters of Quality Measures

Parameters of Quality Measures

The following table describes the parameters of the standard quality measures. Some values might be rounded. The value inf represents a value larger than any other one.

Quality	Parameter	Type	Default Value
contour	measure	measure_e	measure_e.MEAN
bright_on_dark_contrast	ring_thickness_ext	int	1
	ring_thickness_int	int	inf
	normalized	bool	False
dark_on_bright_contrast	ring_thickness_ext	int	1
	ring_thickness_int	int	inf
	normalized	bool	False
bright_on_dark_gradient	max_hole_size	float	1.0
dark_on_bright_gradient	max_hole_size	float	1.0

Signal Transformations

The signal transformation associated with a quality measure is never explicit in a configuration file since it is hardcoded. For the sake of information, the transformation-quality associations are:

• Contour quality measure: the signal is used as is.
• Contrast-based quality measures: the signal is used as is.
• Gradient-based quality measures: the transformation computes the gradient of the signal. It has an optional parameters: unitary. If True, the signal gradient will be normalized. In other words, the quality measures will not depend on the gradient norm, but only its direction.