Correlation/convolution of image by filter
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)
correlate(im, filter, dirichlet = TRUE, normalise = FALSE) convolve(im, filter, dirichlet = TRUE, normalise = FALSE)
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) |
convolve: convolve image with filter
#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")
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