imager (version 0.14)

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, boundary_conditions = TRUE, normalise = FALSE)

Arguments

im

an image

filter

= the correlation kernel.

boundary_conditions

= the border condition type (0=zero, 1=dirichlet)

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")