pcontrastaggregation

Performs pixel aggregation based on contrast criterion.

Synopsis

pcontrastaggregation connexity threshold [-m mask] [rg_in|-] [im_in|-] [rg_out|-]

Description

pcontrastaggregation builds a new region map from aggregation of pixels to regions of the input region map rg_in. A pixel p is aggregated to a region R if:

p is connected to the region R according to the specified connexity;
|contrast(R)-contrast(R+im_in[p])| ≤ threshold.

The contrast is approximated by:

   contrast(R)=MAX(r)-MIN(R)

The contrast of the region is not updated with the new pixel to avoid moving away too much from the initial situation. One prefer iterative executions of the operator to update the inner contrast. For example, operator can be iterated until pstatus returns 0.

The output region map rg_out has the same number of labels than the input region map.

Parameters

connexity specifies the neighbor relation between pixel and region (4 or 8 for 2D; 6 or 26 for 3D).
threshold specifies the maximum variance value to decide to aggregate a pixel to the region. Values are from the gray scale of the input image.

Inputs

rg_in: a region map.
im_in: a grayscale image.

Outputs

rg_out: a region map.

Result

Returns the number of aggregation or FAILURE.

Examples

Aggregates pixels to tangram pieces:

   pbinarization 96 1e30 tangram.pan a.pan
   plabeling 8 a.pan b.pan
   pcontrastaggregation 8 20 b.pan tangram.pan out.pan

C++ prototype

Errc PContrastAggregation( const Reg2d &rg_in, const Img2duc &im_in, Reg2d &rg_out, int connexity, Uchar threshold );

Version française

Croissance des régions d'une carte selon le contraste intérieur.

Author: Régis Clouard