EDGEBLUR

Description

EDGEBLUR is used typically to blur harsh edges in a digital surface model (DSM) (or true) orthorectified-image mosaic along elevation jumps, such as those along building or tree edges.

Parameters

edgeblur(filedem, dbec, filo, dbimage, demfilt)

Name	Type	Caption	Length	Value range
FILEDEM *	str	Geocoded DSM to use to find elevation jumps	1 -
DBEC *	List[int]	Input DSM channel	1 - 1
FILO *	str	File name of image (mosaic) to process	1 -
DBIMAGE	List[int]	Image channels to process	0 - 8
DEMFILT *	str	Filter level	1 -

* Required parameter

Parameter descriptions

FILEDEM

The path and file name of the geocoded DSM file to use to produce the true-orthorectified or DSM-orthorectified image mosaic.

The file must be of the same resolution and projection as the image mosaic specified for FILO, though the extents can differ.

DBEC

The input channel that contains the DSM or digital elevation model (DEM) to examine for large elevation changes.

FILO

The path and file name of an existing output imagery file.

The files specified for FILEDEM and FILO be of the same resolution and projection, though the extents can differ.

DBIMAGE

The imagery channels in which to blur edges along an elevation jump.

If no value is specified for this parameter, all bands in the file are processed. The imagery channels will be overwritten.

DEMFILT

The level of filtering to apply in edge blurring.

Details

True-orthorectified (or DSM-orthorectified) airphoto (or UAV) mosaics often have harsh, unnatural-looking, edges along the edges of buildings and and trees where there are large, sharp, elevation changes. By applying a blurring filter only along these edges a more pleasing natural appearance is achieved and small errors become less noticeable. The vast majority of the image pixels remains unchanged.

EDGEBLUR applies a small (3 x 3) Gaussian smoothing filter on the imagery data (specified in FILO and DBIMAGE), as guided by large elevation jumps in the DSM file (FILEDEM and DBEC). A large elevation jump is assumed to be four times the imagery resolution or 1.5 meters, whichever is greater.

Typically, the DEM file specified in FILEDEM is a DSM generated from a stereo-airphoto project and is the same one used in generating the true-orthorectified imagery. The file specified for FILEDEM and FILO must be of the same resolution and projection, though the extents can differ.

The strength of the filtering (blurring) applied along the edges can be specified in DEMFILT. LOW applies a very light, 3 x 3 Gaussian blur, MEDIUM applies a heavier, 3 x 3 Gaussian blur, and HIGH applies the medium filter twice.

Example

You have a RGB true-orthorectified image mosaic (image_mosaic.pix) and the DSM-elevation file (dsm.pix) used to produce the true-orthorectified images. Both files must be of the same projection and resolution.

from pci.edgeblur import edgeblur

filedem  = r"dsm.pix"  
dbec     = [1]
filo     = r"image_mosaic.pix"
dbimage  = [1,2,3]
demfilt  = r"medium"

edgeblur(filedem, dbec, filo, dbimage, demfilt)