fix lazy-loading for tiled images with multiple slices

src/types/lazy.jl

@@ -39,6 +39,11 @@ mutable struct LazyBufferedTIFF{T <: ColorOrTuple, O <: Unsigned, AA <: Abstract
     """
     An internal cache to fill reading from disk
     """
+    working_cache::AA
+
+    """
+    An internal cache to fill with fully transformed data
+    """
     cache::AA
 
     """
@@ -57,7 +62,7 @@ mutable struct LazyBufferedTIFF{T <: ColorOrTuple, O <: Unsigned, AA <: Abstract
     readonly::Bool
 
     function LazyBufferedTIFF(file::TiffFile{O}, ifds::Vector{IFD{O}}, dims, cache::AA, cache_index::Int, last_ifd_offset::O, readonly::Bool) where {O, AA <: AbstractArray}
-        new{eltype(cache), O, typeof(cache)}(file, ifds, dims, cache, cache_index, last_ifd_offset, readonly)
+        new{eltype(cache), O, typeof(cache)}(file, ifds, dims, cache, cache, cache_index, last_ifd_offset, readonly)
     end
 end
 
@@ -124,9 +129,9 @@ function Base.getindex(A::LazyBufferedTIFF{T, O, AA}, i1::Int, i2::Int, i::Int)
             A.file.io = getstream(format"TIFF", open(path), path)
         end
 
-        read!(A.cache, A.file, ifd)
+        read!(A.working_cache, A.file, ifd)
 
-        A.cache = transform(A.cache, ifd)
+        A.cache = transform(A.working_cache, ifd)
 
         A.cache_index = i
     end

test/runtests.jl

@@ -222,8 +222,14 @@ end
 @testset "Tiled" begin
     uncompressed = get_example("shapes_uncompressed.tif")
     compressed_tiled = get_example("shapes_lzw_tiled.tif")
-    @test TiffImages.load(uncompressed) == TiffImages.load(compressed_tiled)
-    @test TiffImages.load(uncompressed)[:] == TiffImages.load(compressed_tiled; lazyio=true)[:]
+    compressed_tiled_multi = get_example("shapes_tiled_multi.tif")
+    uncompressed_loaded = TiffImages.load(uncompressed)
+    compressed_tiled_multi_loaded = TiffImages.load(compressed_tiled_multi; lazyio=true)
+    @test uncompressed_loaded == TiffImages.load(compressed_tiled)
+    @test uncompressed_loaded[:] == TiffImages.load(compressed_tiled; lazyio=true)[:]
+    @test compressed_tiled_multi_loaded[:,:,1] == uncompressed_loaded
+    @test compressed_tiled_multi_loaded[:,:,2] == uncompressed_loaded
+    @test compressed_tiled_multi_loaded[:,:,3] == uncompressed_loaded
 end
 
 @testset "Planar" begin