offset generic array back to 1-based indexing array

src/Sixel.jl

@@ -3,6 +3,7 @@ module Sixel
 export sixel_encode, sixel_decode
 
 using ImageCore
+using OffsetArrays
 using IndirectArrays # sixel sequence is actually an indexed image format
 
 import REPL: Terminals

src/encoder.jl

@@ -63,6 +63,9 @@ sixel_encode(io::IO, img::AbstractVector, enc::SEC=default_encoder(img); kwargs.
     sixel_encode(io, reshape(img, :, 1), enc; kwargs...)
 
 function sixel_encode(io::IO, img::AbstractArray, enc::SEC=default_encoder(img); transpose=false, kwargs...)
+    # Conversion from OffsetArrays to Array is not very well supported, so we have to de-offset first.
+    img = OffsetArrays.no_offset_view(img)
+
     # make sure it always tiles along row order
     @assert ndims(img) >= 3
     nrow = transpose ? prod(size(img)[3:end]) : 1
@@ -76,6 +79,8 @@ function sixel_encode(
         img::AbstractMatrix,
         enc::SEC=default_encoder(img);
         transpose=false, kwargs...)
+    # Conversion from OffsetArrays to Array is not very well supported, so we have to de-offset first.
+    img = OffsetArrays.no_offset_view(img)
     if enc isa LibSixelEncoder
         T = canonical_sixel_eltype(enc, eltype(img))
         AT = Array{T, ndims(img)}

test/Project.toml

@@ -6,5 +6,6 @@ ImageMagick = "6218d12a-5da1-5696-b52f-db25d2ecc6d1"
 ImageQualityIndexes = "2996bd0c-7a13-11e9-2da2-2f5ce47296a9"
 IndirectArrays = "9b13fd28-a010-5f03-acff-a1bbcff69959"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
+OffsetArrays = "6fe1bfb0-de20-5000-8ca7-80f57d26f881"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 TestImages = "5e47fb64-e119-507b-a336-dd2b206d9990"

test/backend/libsixel.jl

@@ -214,6 +214,25 @@
         sixel_encode(io, img, transpose=false)
         @test bufferdata == String(take!(io))
     end
+
+    @testset "OffsetArray" begin
+        enc = Sixel.LibSixelEncoder()
+        for img in [
+            repeat(distinguishable_colors(10), inner=(10, )),
+            repeat(distinguishable_colors(10), inner=(10, 50)),
+            repeat(distinguishable_colors(5), inner=(20, 50, 3))
+        ]
+            io = IOBuffer()
+            sixel_encode(io, img, enc)
+            ref = String(take!(io))
+
+            imgo = OffsetArray(img, OffsetArrays.Origin(0))
+            io = IOBuffer()
+            sixel_encode(io, imgo, enc)
+            actual = String(take!(io))
+            @test ref == actual
+        end
+    end
 end
 
 @testset "decoder" begin

test/runtests.jl

@@ -1,6 +1,6 @@
 using Sixel
 using Test
-using ImageCore, IndirectArrays
+using ImageCore, IndirectArrays, OffsetArrays
 using ImageQualityIndexes
 using LinearAlgebra
 using FileIO, TestImages