pperimeterselection

Selects regions from perimeter length.

Synopsis

pperimeterselection relation threshold [-m mask] [rg_in|-] [rg_out|-]

Description

pperimeterselection selects regions from their perimeter length. The parameter relation specifies the order relation to the threshold value that is used to select or not a region.

The region perimeter is the number of pixels on the region boundary. The algorithm uses one quarter pixel for concavity. For example, the perimeter is 7 pixels for the following region (7=6+4*0.25) :

    xx
   xxxx
    xx

For a region with 1 pixel, the perimeter is 1.

Parameters

relation is an integer from [-3,3] which specifies the order relation to the threshold value:
- relation = 3: regions with the maximum value.
- relation = 2: regions >= threshold.
- relation = 1: regions > threshold.
- relation = 0: regions = threshold.
- relation = -1: regions < threshold.
- relation = -2: regions <= threshold.
- relation = -3: regions with the minimum value.
threshold is a positive integer defined in pixel unit.

Inputs

rg_in: a 2D region map.

Outputs

rg_out: a 2D region map.

Result

Returns the number of selected regions.

Examples

Selects regions that have a boundary > 50 pixels:

   pperimeterselection 1 50 rin.pan rout.pan

C++ prototype

Errc PPerimeterSelection( const Reg2d &rg_in, Reg2d &rg_out, int relation, Ulong threshold );

Version française

Sélection de régions sur leur valeur de périmètre.

Author: Régis Clouard