pregioneulernumber

Measures region Euler number.

Synopsis

pregioneulernumber name [rg_in|-] [col_out|-]

Description

pregioneulernumber measures the Euler number of the regions inside the region map rg_in. Each region Euler number is stored as a long value in the array named name inside the collection col_out. The ith item in the array corresponds to the i+1th region because the region 0 is not considered.

The Euler number for a region is defined as 1 - the number of holes in the region.

The algorithm used to calculated the Euler number rests on the local operation:
Let X(R) the number of the following 2x2 patterns (r region label for region R, et 0 other labels):

0 0
0 r

Let V(R) the number of the following 2x2 pattern

0 r
r r

then Euler(R) = X(R) - V(R)

Parameters

name is a string that contains the name of the array inside the collection.

Inputs

rg_in: a 2D region map.

Outputs

col_out: a collection.

Result

Returns SUCCESS or FAILURE.

Examples

Displays euleur number of the regions yielded by a simple binarization of tangram.pan:

   pbinarization 100 1e30 tangram.pan a.pan
   plabeling 8 a.pan b.pan
   pregioneulernumber eulernumber b.pan c.pan
   pcol2txt c.pan

C++ prototype

Errc PRegionEulerNumber( const Reg2d &rg_in, Collection &cold, const std::string &name );

Version française

Calcul du nombre d'Euler des régions.

Author: Régis Clouard