Image hash with DB

Mix.install([
  {:ecto, "~> 3.10"},
  {:ecto_sql, "~> 3.10"},
  {:jason, "~> 1.4"},
  {:postgrex, "~> 0.17.3"},
  {:image, "~> 0.38"},
  {:req, "~> 0.3"},
  {:kino, "~> 0.12"}
])

画像の準備

# 元画像
original_img =
  "https://www.elixirconf.eu/assets/images/drops.svg"
  |> Req.get!()
  |> Map.get(:body)
  |> Image.from_binary!()

# グレースケール
gray_img = Image.to_colorspace!(original_img, :bw)

# リサイズ
resized_img = Image.resize!(original_img, 0.5)

# 回転
rotated_img = Image.rotate!(original_img, 45)

# 切り取り
cropped_img = Image.crop!(original_img, 0.07, 0.07, 0.9, 0.9)

# 文字追加
text_img = Image.Text.text!("Elixir", text_fill_color: :purple)
with_text_img = Image.compose!(original_img, text_img, x: 300, y: 100)

# 別画像
other_img =
  "https://hexdocs.pm/phoenix/assets/logo.png"
  |> Req.get!()
  |> Map.get(:body)
  |> Image.from_binary!()

img_list =
  [
    %{name: "original_img", image: original_img},
    %{name: "gray_img", image: gray_img},
    %{name: "resized_img", image: resized_img},
    %{name: "rotated_img", image: rotated_img},
    %{name: "cropped_img", image: cropped_img},
    %{name: "with_text", image: with_text_img},
    %{name: "other", image: other_img}
  ]

img_list
|> Enum.map(fn %{name: name, image: img} ->
  Kino.Layout.grid([name, img], columns: 1)
end)
|> Kino.Layout.grid(columns: 4)

ハッシュの計算

img_list =
  Enum.map(img_list, fn %{image: img} = map ->
    Map.merge(map, %{dhash: Image.dhash(img) |> elem(1)})
  end)

DB 準備

defmodule Repo do
  use Ecto.Repo,
    otp_app: :my_notebook,
    adapter: Ecto.Adapters.Postgres
end

opts = [
  hostname: "postgres_for_livebook",
  port: 5432,
  username: "postgres",
  password: System.fetch_env!("LB_DB_PASSWORD"),
  database: "postgres"
]

Kino.start_child({Repo, opts})

defmodule Migrations.CreateImageTable do
  use Ecto.Migration

  def change do
    create table(:image) do
      add(:name, :string)
      add(:dhash, :bit, size: 64)
    end
  end
end

Ecto.Migrator.up(Repo, 11, Migrations.CreateImageTable)

DB への登録

defmodule ImageSchema do
  use Ecto.Schema

  schema "image" do
    field(:name, :string)
    field(:dhash, :binary)
  end
end

img_list
|> Enum.map(fn map ->
  Map.delete(map, :image)
end)
|> then(&Repo.insert_all(ImageSchema, &1))

Repo.all(ImageSchema)

類似画像の検索

query =
  """
  SELECT
    src.name as src_name,
    dst.name as dst_name,
    bit_count(src.dhash # dst.dhash) as humming_distance
  FROM
    image AS src
  INNER JOIN
    image AS dst
  ON
    src.id < dst.id
  AND
    bit_count(src.dhash # dst.dhash) < 20
  ORDER BY
    humming_distance ASC
  """

{:ok, result} = Ecto.Adapters.SQL.query(Repo, query, [])

result.rows
|> Enum.map(fn [src_img_name, dst_img_name, distance] ->
  src_img = Enum.find(img_list, fn map -> map.name == src_img_name end) |> Map.get(:image)
  dst_img = Enum.find(img_list, fn map -> map.name == dst_img_name end) |> Map.get(:image)

  [
    distance,
    Kino.Layout.grid([src_img, dst_img], columns: 2)
  ]
  |> Kino.Layout.grid(columns: 1)
end)
|> Kino.Layout.grid(columns: 4)