Add findall_window

src/ImageFiltering.jl

@@ -16,7 +16,7 @@ export Kernel, KernelFactors,
     BorderArray,
     Algorithm,
     imfilter, imfilter!,
-    mapwindow, mapwindow!,
+    mapwindow, mapwindow!, findall_window,
     imgradients, padarray, centered, kernelfactors, reflect,
     freqkernel, spacekernel,
     findlocalminima, findlocalmaxima,
@@ -89,6 +89,7 @@ include("specialty.jl")
 include("mapwindow.jl")
 using .MapWindow
 include("extrema.jl")
+include("findall_window.jl")
 
 function __init__()
     # See ComputationalResources README for explanation

src/findall_window.jl

@@ -0,0 +1,51 @@
+"""
+    findall_window(f, img::AbstractArray{T,N}, window::Dims{N}; allow_edges::(true...,))
+
+Return the list of window-centers for which `f(V, basepoint)` returns `true` for windowed-views `V`
+"centered" on `basepoint`. At the edge of `img`, `basepoint` may not actually be in the center of `V`.
+"""
+function findall_window(f::F, img::AbstractArray{T,N}, window::Dims{N}; allow_edges::NTuple{N,Bool}=ntuple(_->true, N)) where {F,T<:Union{Gray,Number},N}
+    basepoints = Vector{CartesianIndex{N}}(undef, 0)
+    Iedge = CartesianIndex(map(!, allow_edges))
+    R0 = CartesianIndices(img)
+    R = clippedinds(R0, Iedge)
+    halfwindow = CartesianIndex(map(x -> x >> 1, window))
+    for i in R
+        Rview = _colon(i-halfwindow, i+halfwindow) ∩ R0
+        if f(OffsetArray(@inbounds(view(img, Rview)), Rview.indices), i)
+            push!(basepoints, i)
+        end
+    end
+    return basepoints
+end
+
+"""
+    all_window(f, V, basepoint, excludepoint=nothing)
+
+Returns `true` if `f(img[centerpoint], img[otherpoint])` for all indices `otherpoint`.
+Optionally exclude a single point (e.g., `basepoint` itself) by setting `excludepoint`.
+"""
+@inline function all_window(f::F, V::AbstractArray, basepoint::CartesianIndex, excludepoint::Union{Nothing,CartesianIndex}=nothing) where F
+    @inbounds ref = V[basepoint]
+    @inbounds for (i, v) in pairs(V)
+        i == excludepoint || f(ref, v) || return false
+    end
+    return true
+end
+
+"""
+    ismax_window(V, basepoint)
+
+Returns `true` if `V[basepoint] > V[otherpoint]` for all indices `otherpoint != basepoint` in `V`.
+"""
+@inline ismax_window(V, i) = all_window(>, V, i, i)
+
+"""
+    ismin_window(V, basepoint)
+
+Returns `true` if `V[basepoint] < V[otherpoint]` for all indices `otherpoint != basepoint` in `V`.
+"""
+@inline ismin_window(V, i) = all_window(<, V, i, i)
+
+findmax_window(A, window; kwargs...) = findall_window(ismax_window, A, window; kwargs...)
+findmin_window(A, window; kwargs...) = findall_window(ismin_window, A, window; kwargs...)