imager (version 0.31)

correlate: Correlation of image by filter

Description

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

Usage

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

Arguments

im

an image

filter

the correlation kernel.

dirichlet

boundary condition (FALSE=zero padding, TRUE=dirichlet). Default FALSE

normalise

normalise filter (default FALSE)

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")