Skip to content

r.grow

Generates a raster map layer with contiguous areas grown by one cell.

r.grow [-m] input=name output=name [radius=float] [metric=string] [old=integer] [new=integer] [--overwrite] [--verbose] [--quiet] [--qq] [--ui]

Example:

r.grow input=name output=name

grass.script.run_command("r.grow", input, output, radius=1.01, metric="euclidean", old=None, new=None, flags=None, overwrite=False, verbose=False, quiet=False, superquiet=False)

Example:

gs.run_command("r.grow", input="name", output="name")

Parameters

input=name [required]
    Name of input raster map
output=name [required]
    Name for output raster map
radius=float
    Radius of buffer in raster cells
    Default: 1.01
metric=string
    Metric
    Allowed values: euclidean, maximum, manhattan
    Default: euclidean
old=integer
    Value to write for input cells which are non-NULL (-1 => NULL)
new=integer
    Value to write for "grown" cells
-m
    Radius is in map units rather than cells
--overwrite
    Allow output files to overwrite existing files
--help
    Print usage summary
--verbose
    Verbose module output
--quiet
    Quiet module output
--qq
    Very quiet module output
--ui
    Force launching GUI dialog

input : str, required
    Name of input raster map
    Used as: input, raster, name
output : str, required
    Name for output raster map
    Used as: output, raster, name
radius : float, optional
    Radius of buffer in raster cells
    Default: 1.01
metric : str, optional
    Metric
    Allowed values: euclidean, maximum, manhattan
    Default: euclidean
old : int, optional
    Value to write for input cells which are non-NULL (-1 => NULL)
new : int, optional
    Value to write for "grown" cells
flags : str, optional
    Allowed values: m
    m
        Radius is in map units rather than cells
overwrite: bool, optional
    Allow output files to overwrite existing files
    Default: False
verbose: bool, optional
    Verbose module output
    Default: False
quiet: bool, optional
    Quiet module output
    Default: False
superquiet: bool, optional
    Very quiet module output
    Default: False

DESCRIPTION

r.grow adds cells around the perimeters of all areas in a user-specified raster map layer and stores the output in a new raster map layer. The user can use it to grow by one or more than one cell (by varying the size of the radius parameter), or like r.buffer, but with the option of preserving the original cells (similar to combining r.buffer and r.patch).

If radius is negative,r.grow shrinks areas by removing cells around the perimeters of all areas.

NOTES

The user has the option of specifying three different metrics which control the geometry in which grown cells are created, (controlled by the metric parameter): Euclidean, Manhattan, and Maximum.

The Euclidean distance or Euclidean metric is the "ordinary" distance between two points that one would measure with a ruler, which can be proven by repeated application of the Pythagorean theorem. The formula is given by:

d(dx,dy) = sqrt(dx^2 + dy^2)

Cells grown using this metric would form isolines of distance that are circular from a given point, with the distance given by the radius.

The Manhattan metric, or Taxicab geometry, is a form of geometry in which the usual metric of Euclidean geometry is replaced by a new metric in which the distance between two points is the sum of the (absolute) differences of their coordinates. The name alludes to the grid layout of most streets on the island of Manhattan, which causes the shortest path a car could take between two points in the city to have length equal to the points' distance in taxicab geometry. The formula is given by:

d(dx,dy) = abs(dx) + abs(dy)

where cells grown using this metric would form isolines of distance that are rhombus-shaped from a given point.

The Maximum metric is given by the formula

d(dx,dy) = max(abs(dx),abs(dy))

where the isolines of distance from a point are squares.

If there are two cells which are equal candidates to grow into an empty space, r.grow will choose the northernmost candidate; if there are multiple candidates with the same northing, the westernmost is chosen.

EXAMPLE

In this example, the lakes map in the North Carolina sample dataset is buffered:

g.region raster=lakes -p
# the lake raster map pixel resolution is 10m
r.grow input=lakes output=lakes_grown_100m radius=10

Shrinking instead of growing:

g.region raster=lakes -p
# the lake raster map pixel resolution is 10m
r.grow input=lakes output=lakes_shrunk_100m radius=-10

SEE ALSO

r.buffer, r.grow.distance, r.patch

Wikipedia Entry: Euclidean Metric
Wikipedia Entry: Manhattan Metric

AUTHORS

Marjorie Larson, U.S. Army Construction Engineering Research Laboratory

Glynn Clements

SOURCE CODE

Available at: r.grow source code (history)
Latest change: Friday Feb 07 19:16:09 2025 in commit a82a39f