# ForwardDiff and ImageTransformations
**URL:** https://discourse.julialang.org/t/forwarddiff-and-imagetransformations/62373
**Category:** General Usage
**Tags:** images, forwarddiff
**Created:** [June 4, 2021, 4:18am UTC](https://discourse.julialang.org/t/forwarddiff-and-imagetransformations/62373 "2021-06-04T04:18:02Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Arrigo\_Benedetti](https://discourse.julialang.org/u/Arrigo_Benedetti)
#### Post date: [June 4, 2021, 4:18am UTC](https://discourse.julialang.org/t/forwarddiff-and-imagetransformations/62373/1 "2021-06-04T04:18:02Z")
I am trying to compute the gradient of a cost function defined as the Sum of Square Differences (SSD) between two images with respect to the parameters of an image transformation. In the code shown below, one of the images has been translated by a small amount. This is basically just a toy problem that I designed to understand if `ForwardDiff.jl` and `ImageTransformations.jl` play well together. Eventually, I will compute derivatives relative the parameters of different image warps:
```julia
using Images
using TestImages
using ImageTransformations
using ForwardDiff
img1 = testimage("cameraman.tif")
y_shift = 0.33
x_shift = -1.76
t = ImageTransformations.Translation(y_shift, x_shift)
img2 = ImageTransformations.warp(img1, t, ImageTransformations.indices_spatial(img1), 0)
function cost(Δ::Vector{T}) where T <: Real
t = ImageTransformations.Translation(Δ[2], Δ[1])
img2 = ImageTransformations.warp(img1, t, ImageTransformations.indices_spatial(img1), 0)
imgg1 = Gray.(img1)
imgg2 = Gray.(img2)
mat1 = convert(Array{Float64}, imgg1)
mat2 = convert(Array{Float64}, imgg2)
@. mat1 = (mat1 - mat2)^2
SSD = sum(vec(mat1))
return SSD
end
```
I’m getting this error:
```julia
StackOverflowError:
Stacktrace:
[1] make_typealias(x::Type)
@ Base ./show.jl:531
[2] show_typealias(io::IOBuffer, x::Type)
@ Base ./show.jl:661
[3] show(io::IOBuffer, x::Type)
@ Base ./show.jl:816
[4] show_datatype(io::IOBuffer, x::DataType)
@ Base ./show.jl:928
[5] show(io::IOBuffer, x::Type)
@ Base ./show.jl:819
[6] print(io::IOBuffer, x::Type)
@ Base ./strings/io.jl:35
[7] print_to_string(::String, ::Vararg{Any, N} where N)
@ Base ./strings/io.jl:135
[8] string
@ ./strings/io.jl:174 [inlined]
[9] floattype
@ ~/.julia/packages/FixedPointNumbers/HAGk2/src/deprecations.jl:4 [inlined]
[10] _default_digits(#unused#::Type{ForwardDiff.Dual{ForwardDiff.Tag{typeof(cost), Float64}, Float64, 2}}) (repeats 43235 times)
@ ImageTransformations ~/.julia/packages/ImageTransformations/xYRLH/src/autorange.jl:82
[11] __round(x::StaticArrays.SVector{2, ForwardDiff.Dual{ForwardDiff.Tag{typeof(cost), Float64}, Float64, 2}})
@ ImageTransformations ~/.julia/packages/ImageTransformations/xYRLH/src/autorange.jl:100
[12] (::ImageTransformations.var"#6#7"{Base.Iterators.Pairs{Union{}, Union{}, Tuple{}, NamedTuple{(), Tuple{}}}, CoordinateTransformations.Translation{StaticArrays.SVector{2, ForwardDiff.Dual{ForwardDiff.Tag{typeof(cost), Float64}, Float64, 2}}}})(i::Int64)
@ ImageTransformations ~/.julia/packages/ImageTransformations/xYRLH/src/autorange.jl:90
[13] iterate
@ ./generator.jl:47 [inlined]
[14] _collect
@ ./array.jl:691 [inlined]
[15] collect_similar
@ ./array.jl:606 [inlined]
[16] map
@ ./abstractarray.jl:2294 [inlined]
[17] _round(tform::CoordinateTransformations.Translation{StaticArrays.SVector{2, ForwardDiff.Dual{ForwardDiff.Tag{typeof(cost), Float64}, Float64, 2}}}; kwargs::Base.Iterators.Pairs{Union{}, Union{}, Tuple{}, NamedTuple{(), Tuple{}}})
@ ImageTransformations ~/.julia/packages/ImageTransformations/xYRLH/src/autorange.jl:89
[18] _round(tform::CoordinateTransformations.Translation{StaticArrays.SVector{2, ForwardDiff.Dual{ForwardDiff.Tag{typeof(cost), Float64}, Float64, 2}}})
@ ImageTransformations ~/.julia/packages/ImageTransformations/xYRLH/src/autorange.jl:89
[19] warp!(out::Matrix{Gray{N0f8}}, img::Interpolations.FilledExtrapolation{Gray{N0f8}, 2, Interpolations.BSplineInterpolation{Gray{N0f8}, 2, Matrix{Gray{N0f8}}, Interpolations.BSpline{Interpolations.Linear}, Tuple{Base.OneTo{Int64}, Base.OneTo{Int64}}}, Interpolations.BSpline{Interpolations.Linear}, Gray{N0f8}}, tform::CoordinateTransformations.Translation{StaticArrays.SVector{2, ForwardDiff.Dual{ForwardDiff.Tag{typeof(cost), Float64}, Float64, 2}}})
@ ImageTransformations ~/.julia/packages/ImageTransformations/xYRLH/src/warp.jl:92
[20] warp(img::Interpolations.FilledExtrapolation{Gray{N0f8}, 2, Interpolations.BSplineInterpolation{Gray{N0f8}, 2, Matrix{Gray{N0f8}}, Interpolations.BSpline{Interpolations.Linear}, Tuple{Base.OneTo{Int64}, Base.OneTo{Int64}}}, Interpolations.BSpline{Interpolations.Linear}, Gray{N0f8}}, tform::CoordinateTransformations.Translation{StaticArrays.SVector{2, ForwardDiff.Dual{ForwardDiff.Tag{typeof(cost), Float64}, Float64, 2}}}, inds::Tuple{Base.OneTo{Int64}, Base.OneTo{Int64}})
@ ImageTransformations ~/.julia/packages/ImageTransformations/xYRLH/src/warp.jl:88
[21] warp(img::Matrix{Gray{N0f8}}, tform::CoordinateTransformations.Translation{StaticArrays.SVector{2, ForwardDiff.Dual{ForwardDiff.Tag{typeof(cost), Float64}, Float64, 2}}}, inds::Tuple{Base.OneTo{Int64}, Base.OneTo{Int64}}, args::Int64; kwargs::Base.Iterators.Pairs{Union{}, Union{}, Tuple{}, NamedTuple{(), Tuple{}}})
@ ImageTransformations ~/.julia/packages/ImageTransformations/xYRLH/src/warp.jl:101
[22] warp(img::Matrix{Gray{N0f8}}, tform::CoordinateTransformations.Translation{StaticArrays.SVector{2, ForwardDiff.Dual{ForwardDiff.Tag{typeof(cost), Float64}, Float64, 2}}}, inds::Tuple{Base.OneTo{Int64}, Base.OneTo{Int64}}, args::Int64)
@ ImageTransformations ~/.julia/packages/ImageTransformations/xYRLH/src/warp.jl:100
[23] cost(Δ::Vector{ForwardDiff.Dual{ForwardDiff.Tag{typeof(cost), Float64}, Float64, 2}})
@ Main ./In[36]:18
[24] vector_mode_dual_eval(f::typeof(cost), x::Vector{Float64}, cfg::ForwardDiff.GradientConfig{ForwardDiff.Tag{typeof(cost), Float64}, Float64, 2, Vector{ForwardDiff.Dual{ForwardDiff.Tag{typeof(cost), Float64}, Float64, 2}}})
@ ForwardDiff ~/.julia/packages/ForwardDiff/QOqCN/src/apiutils.jl:37
[25] vector_mode_gradient(f::typeof(cost), x::Vector{Float64}, cfg::ForwardDiff.GradientConfig{ForwardDiff.Tag{typeof(cost), Float64}, Float64, 2, Vector{ForwardDiff.Dual{ForwardDiff.Tag{typeof(cost), Float64}, Float64, 2}}})
@ ForwardDiff ~/.julia/packages/ForwardDiff/QOqCN/src/gradient.jl:106
[26] gradient(f::Function, x::Vector{Float64}, cfg::ForwardDiff.GradientConfig{ForwardDiff.Tag{typeof(cost), Float64}, Float64, 2, Vector{ForwardDiff.Dual{ForwardDiff.Tag{typeof(cost), Float64}, Float64, 2}}}, ::Val{true})
@ ForwardDiff ~/.julia/packages/ForwardDiff/QOqCN/src/gradient.jl:19
[27] gradient(f::Function, x::Vector{Float64}, cfg::ForwardDiff.GradientConfig{ForwardDiff.Tag{typeof(cost), Float64}, Float64, 2, Vector{ForwardDiff.Dual{ForwardDiff.Tag{typeof(cost), Float64}, Float64, 2}}}) (repeats 2 times)
@ ForwardDiff ~/.julia/packages/ForwardDiff/QOqCN/src/gradient.jl:17
[28] top-level scope
@ In[37]:1
[29] eval
@ ./boot.jl:360 [inlined]
[30] include_string(mapexpr::typeof(REPL.softscope), mod::Module, code::String, filename::String)
@ Base ./loading.jl:1094
```
Any ideas? Thanks!
---
### Author:  [@longemen3000](https://discourse.julialang.org/u/longemen3000)
#### Post date: [June 5, 2021, 2:30am UTC](https://discourse.julialang.org/t/forwarddiff-and-imagetransformations/62373/2 "2021-06-05T02:30:26Z")
At first glance seems like an error on the display mechanism is the result
---
### Author:  [@mkitti](https://discourse.julialang.org/u/mkitti)
#### Post date: [June 8, 2021, 2:59am UTC](https://discourse.julialang.org/t/forwarddiff-and-imagetransformations/62373/3 "2021-06-08T02:59:35Z")
xref: [ForwardDiff not working for simple 2D linear interpolation · Issue #430 · JuliaMath/Interpolations.jl · GitHub](https://github.com/JuliaMath/Interpolations.jl/issues/430#issuecomment-856281497)