Image Archives in Zarr

Mix.install([
  {:ex_zarr, "~> 1.2"},
  # {:ex_zarr, path: Path.join(__DIR__, "../../..")},
])

Pattern

Treat each chunk as an image tile. Stream with metadata to recover bounds, then write processed tiles back with write_stream/3.

alias ExZarr.Array
alias ExZarr.Gallery.Pack

{:ok, source} =
  Array.create(
    shape: {64, 64},
    chunks: {16, 16},
    dtype: :uint8,
    compressor: :zlib,
    storage: :memory
  )

vals = for i <- 0..(64 * 64 - 1), do: rem(i, 256)
:ok = Array.set_slice(source, Pack.pack(vals, :uint8), start: {0, 0}, stop: {64, 64})

{:ok, output} =
  Array.create(
    shape: {64, 64},
    chunks: {16, 16},
    dtype: :uint8,
    compressor: :zlib,
    storage: :memory
  )

# Invert tiles as a stand-in for image processing
tiles =
  source
  |> Array.stream_chunks(concurrency: 4, metadata: true)
  |> Enum.map(fn %{index: idx, data: tile, metadata: meta} ->
    inverted =
      for <<b::8 <- tile>>, into: <<>> do
        <<255 - b::8>>
      end

    {idx, inverted, meta}
  end)

%{tiles: length(tiles), sample_bounds: tiles |> hd() |> elem(2)}

Each chunk corresponds to a spatial tile. Use metadata: true to recover pixel bounds without separate coordinate math.