Dicom.Codec behaviour (Dicom v0.9.2)

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Behaviour for DICOM pixel data codecs.

Codecs decode compressed pixel data frames to raw (uncompressed) pixel data, and encode raw pixel data to compressed form.

Implementing a codec

defmodule MyJPEGCodec do
  @behaviour Dicom.Codec

  @impl true
  def decode(frame_binary, metadata) do
    # decode JPEG to raw pixels
    {:ok, raw_pixels}
  end

  @impl true
  def encode(raw_pixels, metadata) do
    {:ok, compressed}
  end

  @impl true
  def transfer_syntax_uids do
    ["1.2.840.10008.1.2.4.50", "1.2.840.10008.1.2.4.51"]
  end
end

Metadata

The metadata map carries image parameters needed for decoding/encoding:

  • :rows - image height
  • :columns - image width
  • :bits_allocated - bits per pixel sample (8, 16, 32)
  • :bits_stored - meaningful bits within allocated
  • :high_bit - most significant bit position
  • :pixel_representation - 0 for unsigned, 1 for signed
  • :samples_per_pixel - 1 for grayscale, 3 for RGB
  • :photometric_interpretation - e.g., "MONOCHROME2", "RGB"
  • :planar_configuration - 0 for interleaved, 1 for separate planes

Summary

Types

metadata()

Callbacks

decode(binary, metadata)

Decodes a single compressed frame to raw (uncompressed) pixel data.

encode(binary, metadata)

Encodes raw (uncompressed) pixel data to compressed form.

transfer_syntax_uids()

Returns the list of Transfer Syntax UIDs this codec handles.

Types

metadata()

@type metadata() :: %{
  optional(:rows) => non_neg_integer(),
  optional(:columns) => non_neg_integer(),
  optional(:bits_allocated) => non_neg_integer(),
  optional(:bits_stored) => non_neg_integer(),
  optional(:high_bit) => non_neg_integer(),
  optional(:pixel_representation) => 0 | 1,
  optional(:samples_per_pixel) => non_neg_integer(),
  optional(:photometric_interpretation) => String.t(),
  optional(:planar_configuration) => 0 | 1
}

Callbacks

decode(binary, metadata)

@callback decode(binary(), metadata()) :: {:ok, binary()} | {:error, term()}

Decodes a single compressed frame to raw (uncompressed) pixel data.

encode(binary, metadata)

@callback encode(binary(), metadata()) :: {:ok, binary()} | {:error, term()}

Encodes raw (uncompressed) pixel data to compressed form.

transfer_syntax_uids()

@callback transfer_syntax_uids() :: [String.t()]

Returns the list of Transfer Syntax UIDs this codec handles.