Possible bug with Inner() option

[juliohm]

Consider the following example:

using GeoStatsImages
using ImageFiltering
using Plots

# load an example 100x100 image
img = training_image("Strebelle")[1:100,1:100,1]

# trivial smoothing kernel
kern = ones(30,30)

# works as expected
res = imfilter(img, centered(kern), Algorithm.FFT())
heatmap(res)

# now with the Inner() option
res = imfilter(img, centered(kern), Inner(), Algorithm.FFT())
heatmap(res)

There is some strange offset. Could you please confirm the bug?

[johnnychen94]

For FFT algorithm, kern will be shifted and padded to of the same size of img. Looks like the shifting and padding part doesn't work properly.

[juliohm]

It may also be a simpler bug like indexing the final result incorrectly to produce the inner part of the full image. If the result without inner is a OffsetArray for example doing res[30:100-30,30:100-30] may be innapropriate.

On Fri, Nov 8, 2019, 00:31 Johnny Chen notifications@github.com wrote:

For FFT algorithm, kern will be shifted and padded to of the same size of img. Looks like the shifting and padding part doesn't work properly.

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[juliohm]

Appreciate if someone familiar with the code can take a look at this. ImageFiltering.jl is one of the few packages that I can't contribute straightforwardly, the code is advanced and full of indirect dispatch calls. Tried falling the calls with the debugger, but it still very challenging to find the point where the indexing is going wrong.

[timholy]

Test master. No release yet because we need to figure out the upper bounding of all of JuliaImages, and I haven't had time to do that yet.

[juliohm]

Tests fail for me on master:

However, the issue reported above does not happen.

[timholy]

Weird, it's passing on Travis: https://travis-ci.org/JuliaImages/ImageFiltering.jl?utm_medium=notification&utm_source=github_status

and AppVeyor: https://ci.appveyor.com/project/timholy/imagefiltering-jl/builds/28672293