mlaplacian

Laplacian operator is defined as the difference between external gradient and internal gradient – mgradient(img; mode=:external) - mgradient(img; mode=:internal).

using ImageMorphology
using TestImages
using ImageBase
using ImageShow

img = restrict(testimage_dip3e("fig0940")) # rice
img01 = @. Gray(img > 0.5)
mosaic(img, img01; nrow=1)

mosaic(mlaplacian(img), mlaplacian(img01); nrow=1)

Note that laplacian can produce negative values:

A = falses(7, 7)
A[3:5, 3:5] .= true
A[4, 4] = false
Int.(mlaplacian(A))

7×7 Matrix{Int64}:
 0  0   0   0   0  0  0
 0  1   1   1   1  1  0
 0  1  -1  -1  -1  1  0
 0  1  -1   1  -1  1  0
 0  1  -1  -1  -1  1  0
 0  1   1   1   1  1  0
 0  0   0   0   0  0  0

See also

ImageBase.jl provides the finite-difference version of laplace operator flaplacian. ImageFiltering.jl provides Laplacian and LaplacianOfGaussian kernels.

fout = abs.(ImageBase.FiniteDiff.flaplacian(img))
mout = abs.(mlaplacian(img))
mosaic(fout, mout; nrow=1)

For a comprehensive and more accurate documentation, please check the mlaplacian reference page.

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