# distmap: Distance map transform

## Description

Computes the distance map transform of a binary image.
The distance map is a matrix which contains for each pixel
the distance to its nearest background pixel.
## Usage

distmap(x, metric=c('euclidean', 'manhattan'))

## Arguments

x

An `Image`

object or an array.
`x`

is considered as a binary image, whose pixels of value 0
are considered as background ones and other pixels as
foreground ones.

metric

A character indicating which metric to use, L1 distance (`manhattan`

)
or L2 distance (`euclidean`

). Default is `euclidean`

.

## Value

An `Image`

object or an array, with pixels
containing the distances to the nearest background points.

## Details

A fast algorithm of complexity O(M*N*log(max(M,N))), where (M,N) are the
dimensions of `x`

, is used to compute the distance map.
## References

M. N. Kolountzakis, K. N. Kutulakos. Fast Computation of the Euclidean
Distance Map for Binary Images, Infor. Proc. Letters 43 (1992).## Examples

x = readImage(system.file("images", "shapes.png", package="EBImage"))
display(x)
dx = distmap(x)
display(dx/10, title='Distance map of x')