measure_pairs

Herror ::measure_pairs ( Hobject Image, const HTuple &MeasureHandle, const HTuple &Sigma, const HTuple &Threshold, const HTuple &Transition, const HTuple &Select, HTuple *RowEdgeFirst, HTuple *ColumnEdgeFirst, HTuple *AmplitudeFirst, HTuple *RowEdgeSecond, HTuple *ColumnEdgeSecond, HTuple *AmplitudeSecond, HTuple *IntraDistance, HTuple *InterDistance ) HTuple HImage::MeasurePairs ( const HTuple &MeasureHandle, const HTuple &Sigma, const HTuple &Threshold, const HTuple &Transition, const HTuple &Select, HTuple *ColumnEdgeFirst, HTuple *AmplitudeFirst, HTuple *RowEdgeSecond, HTuple *ColumnEdgeSecond, HTuple *AmplitudeSecond, HTuple *IntraDistance, HTuple *InterDistance ) const

Extract straight edge pairs perpendicular to a rectangle.

::measure_pairs serves to extract straight edge pairs which lie perpendicular to the major axis of a rectangle.

The extraction algorithm is identical to ::measure_pos. In addition the edges are grouped to pairs: If Transition = 'positive', the edge points with a dark-to-light transition in the direction of the major axis of the rectangle are returned in RowEdgeFirst and ColumnEdgeFirst. In this case, the corresponding edges with a light-to-dark transition are returned in RowEdgeSecond and ColumnEdgeSecond. If Transition = 'negative', the behavior is exactly opposite. If Transition = 'all', the first detected edge defines the transition for RowEdgeFirst and ColumnEdgeFirst. If more than one edge with the same transition is found, the first one is used as a pair element. Finally, it is possible to select which edge pairs are returned. If Select is set to 'all', all edge pairs are returned. If it is set to 'first', only the first of the extracted edge pairs is returned, while it is set to 'last', only the last one is returned.

The extracted edges are returned as single points which lie on the major axis of the rectangle. The corresponding edge amplitudes are returned in AmplitudeFirst and AmplitudeSecond. In addition, the distance between each edge pair is returned in IntraDistance and the distance between consecutive edge pairs is returned in InterDistance. Here, IntraDistance[i] corresponds to the distance between EdgeFirst[i] and EdgeSecond[i], while InterDistance[i] corresponds to the distance between EdgeSecond[i] and EdgeFirst[i+1], i.e., the tuple InterDistance contains one element less than the tuples of the edge pairs.

Attention

::measure_pairs only returns meaningful results if the assumptions that the edges are straight and perpendicular to the major axis of the rectangle are fulfilled. Thus, it should not be used to extract edges from curved objects, for example. Furthermore, the user should ensure that the rectangle is as close to perpendicular as possible to the edges in the image.

Parameters

`Image` (input_object)	singlechannelimage `->` Hobject: HImage ( byte )
Input image.

`MeasureHandle` (input_control)	measure_id `->` HTuple.long
Measure object handle.

`Sigma` (input_control)	number `->` HTuple.double
Sigma of gaussian smoothing.
Default value: 1.0
Suggested values: 0.4, 0.6, 0.8, 1.0, 1.5, 2.0, 3.0, 4.0, 5.0, 7.0, 10.0
Typical range of values: `0.4 <= Sigma <= 100` (lin)
Minimum increment: 0.01
Recommended increment: 0.1
Restriction: `Sigma >= 0.4`

`Threshold` (input_control)	number `->` HTuple.double
Minimum edge amplitude.
Default value: 30.0
Suggested values: 5.0, 10.0, 20.0, 30.0, 40.0, 50.0, 60.0, 70.0, 90.0, 110.0
Typical range of values: `1 <= Threshold <= 255` (lin)
Minimum increment: 0.5
Recommended increment: 2

`Transition` (input_control)	string `->` HTuple.char *
Light/dark or dark/light edge.
Default value: 'all'
List of values: 'all', 'positive', 'negative'

`Select` (input_control)	string `->` HTuple.char *
Selection of end points.
Default value: 'all'
List of values: 'all', 'first', 'last'

`RowEdgeFirst` (output_control)	point.y-array `->` HTuple.double *
Row coordinate of the center of the edge.

`ColumnEdgeFirst` (output_control)	point.x-array `->` HTuple.double *
Column coordinate of the center of the edge.

`AmplitudeFirst` (output_control)	real-array `->` HTuple.double *
Edge amplitude of found edges (with sign).

`RowEdgeSecond` (output_control)	point.y-array `->` HTuple.double *
Row coordinate of the center of the edge.

`ColumnEdgeSecond` (output_control)	point.x-array `->` HTuple.double *
Column coordinate of the center of the edge.

`AmplitudeSecond` (output_control)	real-array `->` HTuple.double *
Edge amplitude of found edges (with sign).

`IntraDistance` (output_control)	real-array `->` HTuple.double *
Distance between edges of an edge pair.

`InterDistance` (output_control)	real-array `->` HTuple.double *
Distance between consecutive edge pairs.

Result

If the parameter values are correct the operator ::measure_pairs returns the value H_MSG_TRUE. Otherwise an exception handling is raised.

Possible Predecessors

::gen_measure_rectangle2

Possible Successors

::close_measure

Alternatives

::edges_sub_pix, ::measure_pos

Module

Sub-pixel operators