puniformityquadtree

Synopsis

Description

puniformityquadtree segments the input image im_in into homogeneous regions. Homogeneous regions are regions that have an inner uniformity degree ≤ threshold. Output regions are rectangular.

The principle of the algorithm is as follows:

• At the begin consider the image as the first block.
• If the block violates the uniformity predicate (i.e. inner uniformity ≤ threshold) then split the block into four equally sized sub-blocks and then apply the algorithm recursively on each sub-blocks.

Therefore, the result is composed of rectangular regions.

The uniformity degree is calculated from:

   uniformity(R)= 1 - ( variance(R) / (mean(R)^2) )

For 3D image, the output region map is composed of octree regions.

Parameters

• threshold is the maximum uniformity value to decide if a region is homogeneous or not. Values are from the interval [0..1] where:
  • 1 corresponds to highly uniform regions.
  • 0 corresponds to non uniform regions.

Inputs

• im_in: a grayscale image.

Outputs

• rg_out: a region map.

Result

Returns the number of regions.

Examples

Builds the quadtree of tangram.pan:

   puniformityquadtree 0.9 tangram.pan a.pan

See also

C++ prototype

Version française

Segmentation d'une image par quadtree (ou octree) selon l'uniformité.