LineSegmentDetection - Line segment detection

Detect line segments in raster

Detailed description

This application detects locally straight contours in a image. It is based on Burns, Hanson, and Riseman method and use an a contrario validation approach (Desolneux, Moisan, and Morel). The algorithm was published by Rafael Gromponevon Gioi, Jérémie Jakubowicz, Jean-Michel Morel and Gregory Randall.
The given approach computes gradient and level lines of the image and detects aligned points in line support region. The application allows exporting the detected lines in a vector data.

Parameters

This section describes in details the parameters available for this application. Table [1] presents a summary of these parameters and the parameters keys to be used in command-line and programming languages. Application key is LineSegmentDetection .

[1]Table: Parameters table for Line segment detection.
Parameter Key Parameter Name Parameter Type
in Input Image Input image
out Output Detected lines Output vector data
elev Elevation management Group
elev.dem DEM directory Directory
elev.geoid Geoid File Input File name
elev.default Default elevation Float
norescale No rescaling in [0, 255] Boolean
ram Available RAM (Mb) Int
inxml Load otb application from xml file XML input parameters file
outxml Save otb application to xml file XML output parameters file

Input Image: Input image on which lines will be detected.

Output Detected lines: Output detected line segments (vector data).

[Elevation management]: This group of parameters allows managing elevation values. Supported formats are SRTM, DTED or any geotiff. DownloadSRTMTiles application could be a useful tool to list/download tiles related to a product.

  • DEM directory: This parameter allows selecting a directory containing Digital Elevation Model files. Note that this directory should contain only DEM files. Unexpected behaviour might occurs if other images are found in this directory.
  • Geoid File: Use a geoid grid to get the height above the ellipsoid in case there is no DEM available, no coverage for some points or pixels with no_data in the DEM tiles. A version of the geoid can be found on the OTB website (http://hg.orfeo-toolbox.org/OTB-Data/raw-file/404aa6e4b3e0/Input/DEM/egm96.grd).
  • Default elevation: This parameter allows setting the default height above ellipsoid when there is no DEM available, no coverage for some points or pixels with no_data in the DEM tiles, and no geoid file has been set. This is also used by some application as an average elevation value.

No rescaling in [0, 255]: By default, the input image amplitude is rescaled between [0,255]. Turn on this parameter to skip rescaling.

Available RAM (Mb): Available memory for processing (in MB).

Load otb application from xml file: Load otb application from xml file.

Save otb application to xml file: Save otb application to xml file.

Example

To run this example in command-line, use the following:

otbcli_LineSegmentDetection -in QB_Suburb.png -out LineSegmentDetection.shp

To run this example from Python, use the following code snippet:

#!/usr/bin/python

# Import the otb applications package
import otbApplication

# The following line creates an instance of the LineSegmentDetection application
LineSegmentDetection = otbApplication.Registry.CreateApplication("LineSegmentDetection")

# The following lines set all the application parameters:
LineSegmentDetection.SetParameterString("in", "QB_Suburb.png")

LineSegmentDetection.SetParameterString("out", "LineSegmentDetection.shp")

# The following line execute the application
LineSegmentDetection.ExecuteAndWriteOutput()

Limitations

None

Authors

This application has been written by OTB-Team.

See Also

These additional resources can be useful for further information:

On Line demonstration of the LSD algorithm is available here: http://www.ipol.im/pub/algo/gjmr_line_segment_detector/