Distance Transform

distanceTransform calculates the distance to the closest zero pixel for each pixel of the source image.

Usage

distanceTransform(image, distance_type = "L1", mask_size = 3, target = "new")

Arguments

image

An Image object.

distance_type

A character string indicating the type of distance to be calculated. It can be any of the following:

"L1" (the default):

distance = |x1-x2| + |y1-y2|.

"L2":

the simple euclidean distance.

"C":

distance = max(|x1-x2|,|y1-y2|).

"L12":

L1-L2 metric. distance = 2(sqrt(1+x*x/2) - 1)).

"FAIR":

distance = c^2(|x|/c-log(1+|x|/c)), c = 1.3998.

"WELSCH":

distance = c^2/2(1-exp(-(x/c)^2)), c = 2.9846.

"HUBER":

distance = |x|<c ? x^2/2 : c(|x|-c/2), c=1.345.

mask_size

A numeric value indicating the size of the distance transform mask. It can be any of the following:

0:

used only to indicate the Felzenszwalb algorithm when distance_type = "L2".

3 (the default):

3x3 mask.

5:

5x5 mask.

target

The location where the results should be stored. It can take 3 values:

"new":

a new Image object is created and the results are stored inside (the default).

"self":

the results are stored back into image (faster but destructive).

An Image object:

the results are stored in another existing Image object. This is fast and will not replace the content of image but will replace that of target. Note that target must have the same dimensions as image, must have a single channel, and its bit depth must be either "8U" or "32F".

Value

If target="new", the function returns an Image object. If target="self", the function returns nothing and modifies image in place. If target is an Image object, the function returns nothing and modifies that Image object in place.

An Image object.

Author

Simon Garnier, garnier@njit.edu

Examples

balloon <- image(system.file("sample_img/balloon1.png", package = "Rvision"))
changeColorSpace(balloon, "GRAY", target = "self")
#> NULL
bin <- balloon < 200
dst <- distanceTransform(bin)