How to extract 0-255 arrays 3 RGB layers from a gif file?

General Usage
1

How to extract 0-255 arrays 3 RGB layers from a gif file? What package?

2

FileIO.jl

3 
using Images
img=load("patterns.gif")
imgnew=permutedims(channelview(img), (2,3,1))
size(imgnew)
(626, 626, 3)

imgnew:
626×626×3 Array{N0f8,3} with eltype N0f8

4

The .gif file is a three-dimensional array, of colors {N0f8}. Let’s say a temporal sequence of colored matrices (x, y; t).
To “see” the three layers of a frame, let’s say the 17th, you could do

red.(img[:,:,17])
green.(img[:,:,17])
blue.(img[:,:,17])

or channelview(img[:,:,17])

which is equivalent to do

reinterpret(reshape,N0f8,img[:,:,17])


using ImageShow
using TestImages, Colors
img = testimage("mandrill")


mat=reinterpret(reshape,N0f8,img)

redfy=copy(mat)
redfy[2:3,:,:].=0.
reinterpret(reshape,RGB{N0f8},redfy)

greenfy=copy(mat)
greenfy[[1,3],:,:].=0.
reinterpret(reshape,RGB{N0f8},greenfy)

bluefy=copy(mat)
bluefy[1:2,:,:].=0.
reinterpret(reshape,RGB{N0f8},bluefy)
RGB channels

mandrillo_red
mandrillo_red512×512 204 KB

mandrillo_green
mandrillo_green512×512 207 KB

mandrillo_blue
mandrillo_blue512×512 210 KB

5

You need the color palette?

function gif_palette(filepath::AbstractString)
    error1 = Cint(0)
    gif = LibGif.DGifOpenFileName(filepath, Ref(error1))

    try
        gif == C_NULL && error("failed to open the gif file: null pointer")
        slurp_return = LibGif.DGifSlurp(gif)

        if (slurp_return == LibGif.GIF_ERROR)
            error("failed to read .gif file")
        end

        loaded_gif = unsafe_load(gif)

        img_count = loaded_gif.ImageCount
        components = unsafe_wrap(Array, loaded_gif.SavedImages, loaded_gif.ImageCount)

        # Gif's are palette based and can have upto 256 colors in a image
        colormap = unsafe_load(loaded_gif.SColorMap) # global colormap
        palette = unsafe_wrap(Array, colormap.Colors, colormap.ColorCount)
        return palette
    finally
        LibGif.DGifCloseFile(gif, Ref(error1))
    end
end

Given GIFImages.jl is installed and you use things properly. Also to avoid too much bother, you could just read the GIF with FileIO.jl read and then unique(img) on it to get palette.