adimpro (version 0.6.1)

edges: Image Processing

Description

Edge detection using Laplacian, Sobel, or Robert Cross filter.

Usage

edges(img, type = "Laplacian", ltype=1, abs=FALSE)

Arguments

img

an object of class "adimpro".

type

type of edges detection filter. "Laplacian" (default), "Sobel" , or "Robertcross".

ltype

type of laplacian filter. 1,2,3, or 4

abs

take absolute values of results. This has only an effect for tyoe="Laplacian"

Value

• Array containing the values for the edge detector in each pixel and color channel.

Details

This function applies the Laplacian, Sobel, or Robert Cross filter to the input image img. The filter is applied to each color channel separately. ltype determines the different matrices for Laplacian filter used in the literature. ltype == 1 will use:

conv <- matrix(c(-1,-1,-1,-1,-1, -1,-1,-1,-1,-1, -1,-1,24,-1,-1, -1,-1,-1,-1,-1, -1,-1,-1,-1,-1),5,5) ltype == 2 will use:

conv <- matrix(c(0,-1,0,-1,4,-1,0,-1,0), 3, 3)

ltype == 3 will use:

conv <- matrix(c(-1,-1,-1,-1,8,-1,-1,-1,-1), 3, 3)

ltype == 4 (default) will use:

conv <- matrix(c(1,-2,1,-2,4,-2,1,-2,1), 3, 3)

References

Gonzalez, R.C., and Woods, R.E. (2002). Digital Image Processing. Prentice Hall.

Examples

img <- read.image(system.file("img/wias.ppm",package="adimpro"))
X11(height=5,width=10)
par(mfrow=c(2,4),mar=c(2,2,2,.2),mgp=c(2,1,0))
show.image(img,main="Original Image")
img.edge <- edges(img)
show.image(img.edge,main="Edges in red channel",channel=1)
show.image(img.edge,main="Edges in green channel",channel=2)
show.image(img.edge,main="Edges in blue channel",channel=3)
img.edge <- edges(img)
show.image(img.edge,main="Edges (Laplacian)")
img.edge <- edges(img,abs=TRUE)
show.image(img.edge,main="Edges (abs(Laplacian))")
img.edge <- edges(img,"Sobel")
show.image(img.edge,main="Edges (Sobel)")
img.edge <- edges(img,"Robertcross")
show.image(img.edge,main="Edges (Robertcross)")