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refactor: Use padding built into Interpolations.jl instead of rolling our own #33

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Merged
icweaver merged 1 commit into from
Jul 24, 2026
Merged

refactor: Use padding built into Interpolations.jl instead of rolling our own #33

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2 changes: 2 additions & 0 deletions src/Reproject.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -4,10 +4,12 @@ using FITSIO: FITS, ImageHDU, read_header
using Interpolations:
BSpline,
Constant,
Flat,
InPlace,
Linear,
OnCell,
Quadratic,
extrapolate,
interpolate
using SkyCoords: SkyCoords, FK5Coords, GalCoords, ICRSCoords
using WCS: WCS, WCSTransform, pix_to_world, world_to_pix
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17 changes: 10 additions & 7 deletions src/core.jl
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Expand Up @@ -37,7 +37,6 @@ function reproject(input_data, output_projection; shape_out = nothing, order::In
end

img_out = fill(NaN, shape_out)
array_in = pad_edges(array_in)
itp = interpolator(array_in, order)
shape_in = size(array_in)

Expand Down Expand Up @@ -68,8 +67,8 @@ function reproject(input_data, output_projection; shape_out = nothing, order::In

pix_coord_out = world_to_pix(wcs_out, [rad2deg(SkyCoords.lon(coord_out)), rad2deg(SkyCoords.lat(coord_out))])

if 0.5 <= pix_coord_out[1] <= shape_in[1] - 1.5 && 0.5 <= pix_coord_out[2] <= shape_in[2] - 1.5
img_out[i,j] = itp(pix_coord_out[1] + 1, pix_coord_out[2] + 1)
if 0.5 <= pix_coord_out[1] <= shape_in[1] + 0.5 && 0.5 <= pix_coord_out[2] <= shape_in[2] + 0.5
img_out[i,j] = itp(pix_coord_out[1], pix_coord_out[2])
end
end
end
Expand All @@ -79,18 +78,22 @@ end


"""
interpolator(array_in, order::Int)
interpolator(array_in, order::Int; padding = Flat())

Returns an interpolator with the given array and order of interpolation.

`padding` is the Interpolations.jl boundary condition used for evaluations that
fall in the outer half-pixel border of the array, replacing the edge padding
that was previously applied to a copy of the input.
"""
function interpolator(array_in::AbstractArray, order::Int)
if order == 0
function interpolator(array_in::AbstractArray, order::Int; padding = Flat())
if order == 0
itp = interpolate(array_in, BSpline(Constant()))
elseif order == 1
itp = interpolate(array_in, BSpline(Linear()))
else
itp = interpolate(array_in, BSpline(Quadratic(InPlace(OnCell()))))
end

return itp
return extrapolate(itp, padding)
end
15 changes: 0 additions & 15 deletions src/utils.jl
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Expand Up @@ -20,18 +20,3 @@ function wcs_to_celestial_frame(wcs::WCSTransform)

return radesys
end

"""
pad_edges(array_in::Matrix{T}) where {T}

Pads a given array and creates a border with edge elements.
"""
function pad_edges(array_in::Matrix{T}) where {T}
image = Matrix{T}(undef, size(array_in)[1] + 2, size(array_in)[2] + 2)
image[2:end-1,2:end-1] = array_in
image[2:end-1,1] = array_in[:,1]
image[2:end-1,end] = array_in[:,end]
image[1,:] = image[2,:]
image[end,:] = image[end-1,:]
return image
end
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