Incorrectly export GIF image

[RexWzh]

By save("xxx.gif", bitmat), one should get a white picture, however, the output is black.

using FileIO
save("one.gif", ones(Bool, 200, 200)) # get a black image
load("one.gif") |> iszero # true

More generally, when the rate of zeros is small enough, the ones-matrix is treated as a zeros-matrix.

a = ones(Bool, 200, 200)
# set zero on a small range
ind = rand(1:40000, 300)
a[ind] .= false
save("small.gif", a) 
load("small.gif") |> iszero # true again
# set zero on more place
ind = rand(1:40000, 3000)
a[ind] .= false
save("normal.gif", a) # now we get the right image

---

This issue occurs only in the case of gif, might have to do with the wrapper of ImageMagick.jl?

[ViralBShah]

Right this doesn't have to do with FileIO. ImageMagick.jl is in the process of being updated, so perhaps keep an eye on it.