private package GID.Decoding_JPG is

  use JPEG_defs;

  type JPEG_marker is
  (
    SOI      , --  Start Of Image
    --
    SOF_0    , --  Start Of Frame - Baseline DCT
    SOF_1    , --  Extended sequential DCT
    SOF_2    , --  Progressive DCT
    SOF_3    , --  Lossless (sequential)
    SOF_5    , --  Differential sequential DCT
    SOF_6    , --  Differential progressive DCT
    SOF_7    , --  Differential lossless (sequential)
    SOF_8    , --  Reserved for JPEG extensions
    SOF_9    , --  Extended sequential DCT
    SOF_10   , --  Progressive DCT
    SOF_11   , --  Lossless (sequential)
    SOF_13   , --  Differential sequential DCT
    SOF_14   , --  Differential progressive DCT
    SOF_15   , --  Differential lossless (sequential)
    --
    DHT      , --  Define Huffman Table
    DAC      , --  Define Arithmetic Coding
    DQT      , --  Define Quantization Table
    DRI      , --  Define Restart Interval
    --
    APP_0    , --  JFIF - JFIF JPEG image - AVI1 - Motion JPEG (MJPG)
    APP_1    , --  EXIF Metadata, TIFF IFD format, JPEG Thumbnail (160x120)
    APP_2    , --  ICC color profile, FlashPix
    APP_3    ,
    APP_4    ,
    APP_5    ,
    APP_6    ,
    APP_7    ,
    APP_8    ,
    APP_9    ,
    APP_10   ,
    APP_11   ,
    APP_12   , --  Picture Info
    APP_13   , --  Photoshop Save As: IRB, 8BIM, IPTC
    APP_14   , --  Copyright Entries
    --
    COM      , --  Comments
    SOS      , --  Start of Scan
    EOI        --  End of Image
  );

  YCbCr_set : constant Compo_set:= (Y|Cb|Cr => True, others => False);
  Y_Grey_set: constant Compo_set:= (Y => True, others => False);
  CMYK_set  : constant Compo_set:= (Y|Cb|Cr|I => True, others => False);

  type Segment_head is record
    length : U16;
    kind   : JPEG_marker;
  end record;

  procedure Read(image: in out Image_descriptor; sh: out Segment_head);

  -- SOF - Start Of Frame (the real header)
  procedure Read_SOF(image: in out Image_descriptor; sh: Segment_head);

  procedure Read_DHT(image: in out Image_descriptor; data_length: Natural);
  procedure Read_DQT(image: in out Image_descriptor; data_length: Natural);
  procedure Read_DRI(image: in out Image_descriptor);

  procedure Read_EXIF(image: in out Image_descriptor; data_length: Natural);

  --------------------
  -- Image decoding --
  --------------------

  generic
    type Primary_color_range is mod <>;
    with procedure Set_X_Y (x, y: Natural);
    with procedure Put_Pixel (
      red, green, blue : Primary_color_range;
      alpha            : Primary_color_range
    );
    with procedure Feedback (percents: Natural);
    -- mode: Display_mode; -- nice -> progressive nicely displayed
  --
  procedure Load (
    image     : in out Image_descriptor;
    next_frame:    out Ada.Calendar.Day_Duration
  );

end GID.Decoding_JPG;