segmentation_GRASS_RG: GRASS Region Growing image segmentation

In joaofgoncalves/SegOptim: Optimization of Image Segmentation Parameters for Object-Based Image Analysis (OBIA)

GRASS Region Growing image segmentation

Description

A function providing CLI access to GRASS Region Growing image segmentation algorithm and optimize parameters using genetic algorithms. To use this function, image features used in segmentation must be imported into a GRASS database (importToGRASS).

Usage

segmentation_GRASS_RG(
  x,
  GRASS.path = "grass",
  GRASS.inputRstName,
  GRASS.GISDBASE,
  GRASS.LOCATION_NAME = "demolocation",
  GRASS.MAPSET = "PERMANENT",
  outputSegmRst = NULL,
  Threshold = NULL,
  MinSize = NULL,
  memory = 1024,
  iterations = 20,
  verbose = TRUE
)

Arguments

x	A vector with size two defining the values of segmentation parameters optimized by GA: [1] threshold (float) - difference threshold between 0 and 1. Threshold: 0 merges only identical segments; threshold: 1 merges all. [2] minimum number of cells in a segment (integer) - the final step will merge small segments with their best neighbor; options: 1-100000 (default: 1). If you are using this function outside an optimization context it is better to directly define the segmentation parameters in Threshold and MinSize.
GRASS.path	Defines the initialization path to GRASS .bat file for windows (for example: 'C:/GRASS/grass70') or the .sh or .py file for Linux (usually this should be set to '/usr/bin/grass'). The default is "grass70" which assumes that GRASS is in the path environmental variables and version 7.0.x (which may not be appropriate in most cases and therefore this parameter should be set explicitly).
GRASS.inputRstName	Name of the raster dataset that will be segmented (typically a multi-layered raster dataset with segmentation features in each band).
GRASS.GISDBASE	Name of GRASS GIS database.
GRASS.LOCATION_NAME	Name of GRASS location name (default: "demolocation").
GRASS.MAPSET	Name of GRASS mapset (default: "PERMANENT").
outputSegmRst	A path to the output segmented image exported by GRASS r.out.gdal. The output file can be in any of GDAL formats (default: NULL; in this case the segmenter will internally determine a temporary output folder and file path inside the working directory).
Threshold	Difference threshold between 0 and 1. Threshold: 0 merges only identical segments; threshold: 1 merges all
MinSize	Minimum number of cells in a segment (integer) - the final step will merge small segments with their best neighbor
memory	Memory used to run i.segment (default: 1024Mb).
iterations	Maximum number of iterations (default: 20).
verbose	Output messages? (default: TRUE)

Details

This function uses a batch file defining the batch job (GRASS_BATCH_JOB) and starts GRASS with the appropriate parametrization. The i.segment command is used to run the segmentation. The similarity calculation method uses the default value ("euclidean"). See more info at GRASS manual pages online: i.segment at https://grass.osgeo.org/grass72/manuals/i.segment.html Access to GRASS GIS manuals https://grass.osgeo.org/documentation/manuals/

Value

A list object containing output file paths resulting from the segmentation run. These files will be cleaned after each GA iteration.

joaofgoncalves/SegOptim documentation built on Feb. 5, 2024, 11:10 p.m.