Segmentation

Brief Description

Performs segmentation of an image, and output either a raster or a vector file. In vector mode, large input datasets are supported.

Tags

Segmentation

Long Description

This application allows one to perform various segmentation algorithms on a multispectral image.Available segmentation algorithms are two different versions of Mean-Shift segmentation algorithm (one being multi-threaded), simple pixel based connected components according to a user-defined criterion, and watershed from the gradient of the intensity (norm of spectral bands vector). The application has two different modes that affects the nature of its output.

In raster mode, the output of the application is a classical image of unique labels identifying the segmented regions. The labeled output can be passed to the ColorMapping application to render regions with contrasted colours. Please note that this mode loads the whole input image into memory, and as such can not handle large images.

To segment large data, one can use the vector mode. In this case, the output of the application is a vector file or database. The input image is split into tiles (whose size can be set using the tilesize parameter), and each tile is loaded, segmented with the chosen algorithm, vectorized, and written into the output file or database. This piece-wise behavior ensure that memory will never get overloaded, and that images of any size can be processed. There are few more options in the vector mode. The simplify option allows simplifying the geometry (i.e. remove nodes in polygons) according to a user-defined tolerance. The stitch option tries to stitch together the polygons corresponding to segmented region that may have been split by the tiling scheme.

Parameters

Limitations

In raster mode, the application can not handle large input images. Stitching step of vector mode might become slow with very large input images.
MeanShift filter results depends on the number of threads used.
Watershed and multiscale geodesic morphology segmentation will be performed on the amplitude of the input image.

Authors

OTB-Team

See also

MeanShiftSegmentation

Example of use