# Background Interpolators

Background interpolators provide a method for converting a low-resolution mesh into a low-order high-resolution image.

## Interpolators

Photometry.Background.ZoomInterpolatorType
ZoomInterpolator(factors)

Use a cubic-spline interpolation scheme to increase resolution of a mesh.

factors represents the level of "zoom", so an input mesh of size (10, 10) with factors (2, 2) will have an output size of (20, 20). If only an integer is provided, it will be used as the factor for every axis.

Examples

julia> ZoomInterpolator(2)([1 0; 0 1])
4×4 Matrix{Float64}:
1.0          0.75   0.25   -2.77556e-17
0.75         0.625  0.375   0.25
0.25         0.375  0.625   0.75
-5.55112e-17  0.25   0.75    1.0

julia> ZoomInterpolator(3, 1)([1 0; 0 1])
6×2 Matrix{Float64}:
1.0          -2.77556e-17
1.0          -2.77556e-17
0.666667      0.333333
0.333333      0.666667
-5.55112e-17   1.0
-5.55112e-17   1.0

source
Photometry.Background.IDWInterpolatorType
IDWInterpolator(factors; leafsize=10,  k=8, power=1, reg=0, conf_dist=1e-12)

Use Shepard Inverse Distance Weighing interpolation scheme to increase resolution of a mesh.

factors represents the level of "zoom", so an input mesh of size (10, 10) with factors (2, 2) will have an output size of (20, 20). If only an integer is provided, it will be used as the factor for every axis.

The interpolator can be called with some additional parameter being, leaf_size determines at what number of points to stop splitting the tree further, k which is the number of nearest neighbors to be considered, power is the exponent for distance in the weighing factor, reg is the offset for the weighing factor in denominator, conf_dist is the distance below which two points would be considered as the same point.

Examples

julia> IDWInterpolator(2, k=2)([1 0; 0 1])
4×4 Matrix{Float64}:
1.0   0.75      0.25      0.0
0.75  0.690983  0.309017  0.25
0.25  0.309017  0.690983  0.75
0.0   0.25      0.75      1.0

julia> IDWInterpolator(3, 1; k=2, power=4)([1 0; 0 1])
6×2 Matrix{Float64}:
1.0        0.0
1.0        0.0
0.941176   0.0588235
0.0588235  0.941176
0.0        1.0
0.0        1.0
source