morphology function

Morphology: Erosion or Dilatation of Features on a Raster Map

morphology performs morphological operations on images of class SpatialPixelsDataFrame.

morphology(x, operation = c("erode", "dilate"), nt = 5)

Arguments

• x: a matrix of class SpatialPixelsDataFrame with one column
• operation: a character string indicating the operation to be processed: either "erode" or "dilate"
• nt: the number of times that the operation should be processed

Returns

Returns an object of class SpatialPixelsDataFrame with one column, containing 1 when the pixel belong to one feature of the image and NA otherwise (see examples).

Author(s)

Clement Calenge clement.calenge@ofb.gouv.fr

See Also

SpatialPixelsDataFrame-class for further information on objects of class SpatialPixelsDataFrame.

Examples

data(meuse.grid)
a <- SpatialPixelsDataFrame(points = meuse.grid[c("x", "y")],
                            data = meuse.grid)

## dilatation
toto1 <- morphology(a, operation = "dilate", nt = 1)
toto2 <- morphology(a, operation = "dilate", nt = 2)
toto3 <- morphology(a, operation = "dilate", nt = 3)
toto5 <- morphology(a, operation = "dilate", nt = 5)
colo <- grey((1:5)/6)
image(toto5, col = colo[1])
image(toto3, add = TRUE, col = colo[2])
image(toto2, add = TRUE, col = colo[3])
image(toto1, add = TRUE, col = colo[4])
image(a, add = TRUE)

## erosion
colo <- grey((1:12)/13)
image(a, col = "black")
for (i in 1:12) {
  toto <- morphology(a, operation = "erode", nt = i)
  image(toto, add = TRUE, col = colo[i])
}