num_chord ( Regions : : : NumChords, KFactor, LFactor, MeanLength, Bytes )

Characteristic values for runlength coding of regions.

The operator num_chord calculates for every input region from Regions the number of chords necessary for storing this region with the aid of runlength coding. Furthermore the so-called "K-factor" is determined, which indicates by how much the number of chords differs from the ideal of the square in which this value is 1.0.

The K-factor (KFactor) is calculated according to the formula:

            KFactor = NumChords / sqrt(Area),
wherein Area indicates the area of the region. It should be noted that the K-factor can be smaller than 1.0 (in case of long horizontal regions). The L-factor (LFactor) indicates the mean number of chords for each line index occurring in the region. MeanLength indicates the mean length of the chords. The parameter Bytes indicates how many bytes are necessary for coding the region with runlengths.


Attention

All features calculated by the operator num_chord are not rotation invariant because the runlength coding depends on the direction. The operator num_chord does not serve for calculating shape features but for controlling and analysing the efficiency of the runlength coding.


Parameters

Regions (input_object)
region(-array) -> object
Regions to be examined.

NumChords (output_control)
integer(-array) -> integer
Number of chords.
Assertion: 0 <= NumChords

KFactor (output_control)
real(-array) -> real
Storing factor in relation to a square.
Assertion: 0 <= KFactor

LFactor (output_control)
real(-array) -> real
Mean number of chords per line.
Assertion: 0 <= LFactor

MeanLength (output_control)
real(-array) -> real
Mean length of chords.
Assertion: 0 <= MeanLength

Bytes (output_control)
integer(-array) -> integer
Number of bytes necessary for coding the region.
Assertion: 0 <= Bytes


Complexity

The mean runtime complexity is O(1).


Result

The operator num_chord returns the value TRUE if the input is not empty. If necessary an exception is raised.


Possible Predecessors

threshold__, regiongrowing__, connection, fetch_chord


See also

fetch_chord, chord_distribution



Copyright © 1996-1997 MVTec Software GmbH