Connected component segmentation and object based image filtering of the input image according to user-defined criterions.
This application allows one to perform a masking, connected components segmentation and object based image filtering. First and optionally, a mask can be built based on user-defined criterions to select pixels of the image which will be segmented. Then a connected component segmentation is performed with a user defined criterion to decide whether two neighbouring pixels belong to the same segment or not. After this segmentation step, an object based image filtering is applied using another user-defined criterion reasoning on segment properties, like shape or radiometric attributes. Criterions are mathematical expressions analysed by the MuParser library (http://muparser.sourceforge.net/). For instance, expression ”((b1>80) and intensity>95)” will merge two neighbouring pixel in a single segment if their intensity is more than 95 and their value in the first image band is more than 80. See parameters documentation for a list of available attributes. The output of the object based image filtering is vectorized and can be written in shapefile or KML format. If the input image is in raw geometry, resulting polygons will be transformed to WGS84 using sensor modelling before writing, to ensure consistency with GIS software. For this purpose, a Digital Elevation Model can be provided to the application. The whole processing is done on a per-tile basis for large images, so this application can handle images of arbitrary size.
This section describes in details the parameters available for this application. Table 4.144, page 788 presents a summary of these parameters and the parameters keys to be used in command-line and programming languages. Application key is ConnectedComponentSegmentation.
Parameter key | Parameter type |
Parameter description |
in | Input image |
Input Image |
out | Output vector data |
Output Shape |
mask | String |
Mask expression |
expr | String |
Connected Component Expression |
minsize | Int |
Minimum Object Size |
obia | String |
OBIA Expression |
elev | Group |
Elevation management |
elev.dem | Directory |
DEM directory |
elev.geoid | Input File name |
Geoid File |
elev.default | Float |
Default elevation |
inxml | XML input parameters file |
Load otb application from xml file |
outxml | XML output parameters file |
Save otb application to xml file |
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Input Image The image to segment.
Output Shape The segmentation shape.
Mask expression Mask mathematical expression (only if support image is given)
Connected Component Expression Formula used for connected component segmentation
Minimum Object Size Min object size (area in pixel)
OBIA Expression OBIA mathematical expression
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.
Load otb application from xml file Load otb application from xml file
Save otb application to xml file Save otb application to xml file
To run this example in command-line, use the following:
To run this example from Python, use the following code snippet:
Due to the tiling scheme in case of large images, some segments can be arbitrarily split across multiple tiles.
This application has been written by OTB-Team.