runlength_features

runlength_features ( Regions : : : NumRuns, KFactor, LFactor, MeanLength, Bytes )

Characteristic values for runlength coding of regions.

The operator runlength_features calculates for every input region from Regions the number of runs 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 runs 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 = NumRuns / 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 runs for each line index occurring in the region.

MeanLength indicates the mean length of the runs. The parameter Bytes indicates how many bytes are necessary for coding the region with runlengths.

Attention

All features calculated by the operator runlength_features are not rotation invariant because the runlength coding depends on the direction. The operator runlength_features 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.

`NumRuns` (output_control)	integer(-array) `->` integer
Number of runs.
Assertion: `0 <= NumRuns`

`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 runs per line.
Assertion: `0 <= LFactor`

`MeanLength` (output_control)	real(-array) `->` real
Mean length of runs.
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 runlength_features returns the value 2 (H_MSG_TRUE) if the input is not empty. If necessary an exception handling is raised.

Parallelization Information

runlength_features is reentrant and automatically parallelized (on tuple level).

Possible Predecessors

threshold, regiongrowing, connection, runlength_features

Module

Region processing