Less alloc in TriggsSdika filtering (fix #243)

Putting the string interpolation behind a `@noinline` is the key change,
but it doesn't hurt to hoise the range creation.

Of the few remaining allocations, about half will be fixed by
JuliaLang/julia#43990, as they are another
instance of JuliaLang/julia#35972

src/imfilter.jl

@@ -1312,19 +1312,25 @@ _imfilter_inplace_tuple!(r, out, img, ::Tuple{}, Rbegin, inds, Rend, border) = o
  out, img, kernel::TriggsSdika{T,k,l},
  Rbegin::CartesianIndices, ind::AbstractUnitRange,
  Rend::CartesianIndices, border::AbstractBorder) where {T,k,l}
+
+ @noinline function throw_imfilter_dim(R, n, l)
+ dim = ndims(R)+1
+ throw(DimensionMismatch("size $n of img along dimension $dim is too small for filtering with IIR kernel of length $l"))
+ end
+
  if iscopy(kernel)
  if !(out === img)
  copyto!(out, img)
  end
  return out
  end
  if length(ind) <= max(k, l)
- dim = ndims(Rbegin)+1
- throw(DimensionMismatch("size of img along dimension $dim $(length(ind)) is too small for filtering with IIR kernel of length $(max(k,l))"))
+ throw_imfilter_dim(Rbegin, length(ind), max(k, l))
  end
+ indleft = ind[begin:begin+k-1]
+ indright = ind[end-l+1:end]
  for Iend in Rend
  # Initialize the left border
- indleft = collect(Iterators.take(ind,k))
  for Ibegin in Rbegin
  leftborder!(out, img, kernel, Ibegin, indleft, Iend, border)
  end
@@ -1341,7 +1347,6 @@ _imfilter_inplace_tuple!(r, out, img, ::Tuple{}, Rbegin, inds, Rend, border) = o
  end
  end
  # Initialize the right border
- indright = ind[end-l+1:end]
  for Ibegin in Rbegin
  rightborder!(out, img, kernel, Ibegin, indright, Iend, border)
  end