Support for Grayscale Images

[Evidlo]

I'm trying to use DSP.conv to do some simple image filtering on a grayscale image, but it seems like the datatype is not supported:

using TestImages
using ImageView
using DSP

img = float(testimage("cameraman"))

# build kernel
xs = ys = -2:2
kernel_func(x, y) = exp(1 / sqrt(x^2 + y^2))
kernel = [kernel_func(x, y) for x in xs, y in ys]
kernel[size(kernel) .÷ 2 .+ 1...] = exp(1)

# convolve
result = conv(kernel, img)

ImageView.imshow(result)

ERROR: LoadError: MethodError: no method matching conv(::Array{Float64,2}, ::Array{ColorTypes.Gray{Float32},2})
Closest candidates are:
  conv(::AbstractArray{T,N}, ::AbstractArray{T,N}) where {T<:Union{Complex{Float32}, Complex{Float64}, Float32, Float64}, N} at /home/evan/.julia/packages/DSP/amvJg/src/dspbase.jl:688
  conv(::AbstractArray{var"#s3445",N} where var"#s3445"<:Union{Complex{Float32}, Complex{Float64}, Float32, Float64}, ::AbstractArray{var"#s3444",N} where var"#s3444"<:Union{Complex{Float32}, Complex{Float64}, Float32, Float64}) where N at /home/evan/.julia/packages/DSP/amvJg/src/dspbase.jl:699
  conv(::AbstractArray{var"#s3445",N} where var"#s3445"<:Number, ::AbstractArray{var"#s3444",N} where var"#s3444"<:Union{Complex{Float32}, Complex{Float64}, Float32, Float64}) where N at /home/evan/.julia/packages/DSP/amvJg/src/dspbase.jl:711
  ...
Stacktrace:
 [1] top-level scope at /home/evan/research/2022_focal_drift/convolution_test.jl:14
 [2] include(::String) at ./client.jl:457
 [3] top-level scope at REPL[79]:1
in expression starting at /home/evan/research/2022_focal_drift/convolution_test.jl:14