correlate: Correlation/convolution of image by filter
In imager: Image Processing Library Based on 'CImg'

correlate

R Documentation

Correlation/convolution of image by filter

Description

The correlation of image im by filter flt is defined as: res(x,y,z) = sum_{i,j,k} im(x + i,y + j,z + k)*flt(i,j,k). The convolution of an image img by filter flt is defined to be: res(x,y,z) = sum_{i,j,k} img(x-i,y-j,z-k)*flt(i,j,k)

Usage

correlate(im, filter, dirichlet = TRUE, normalise = FALSE)

convolve(im, filter, dirichlet = TRUE, normalise = FALSE)

Arguments

`im`	an image
`filter`	the correlation kernel.
`dirichlet`	boundary condition. Dirichlet if true, Neumann if false (default TRUE, Dirichlet)
`normalise`	compute a normalised correlation (ie. local cosine similarity)

Functions

convolve(): convolve image with filter

Examples


#Edge filter
filter <- as.cimg(function(x,y) sign(x-5),10,10) 
layout(t(1:2))
#Convolution vs. correlation 
correlate(boats,filter) %>% plot(main="Correlation")
convolve(boats,filter) %>% plot(main="Convolution")

imager documentation built on May 29, 2024, 1:38 a.m.