procedure SetPalette(Value: HPalette);
    function GetActiveColorMap: TGIFColorMap;
    function GetBoundsRect: TRect;
    procedure SetBoundsRect(const Value: TRect);
    procedure DoSetBounds(ALeft, ATop, AWidth, AHeight: integer);
    function GetClientRect: TRect;
    function GetPixel(x, y: integer): BYTE;
    function GetScanline(y: integer): pointer;
    procedure NewBitmap;
    procedure FreeBitmap;
    procedure NewImage;
    procedure FreeImage;
    procedure NeedImage;
    function ScaleRect(DestRect: TRect): TRect;
    function HasMask: boolean;
    function GetBounds(Index: integer): WORD;
    procedure SetBounds(Index: integer; Value: WORD);
    function GetHasBitmap: boolean;
    procedure SetHasBitmap(Value: boolean);
  public
    constructor Create(GIFImage: TGIFImage); override;
    destructor Destroy; override;
    procedure Clear;
    procedure SaveToStream(Stream: TStream); override;
    procedure LoadFromStream(Stream: TStream); override;
    procedure Assign(Source: TPersistent); override;
    procedure Draw(ACanvas: TCanvas; const Rect: TRect;
      DoTransparent, DoTile: boolean);
    procedure StretchDraw(ACanvas: TCanvas; const Rect: TRect;
      DoTransparent, DoTile: boolean);
    procedure Crop;
    procedure Merge(Previous: TGIFSubImage);
    property HasBitmap: boolean read GetHasBitmap write SetHasBitmap;
    property Left: WORD index 1 read GetBounds write SetBounds;
    property Top: WORD index 2 read GetBounds write SetBounds;
    property Width: WORD index 3 read GetBounds write SetBounds;
    property Height: WORD index 4 read GetBounds write SetBounds;
    property BoundsRect: TRect read GetBoundsRect write SetBoundsRect;
    property ClientRect: TRect read GetClientRect;
    property Interlaced: boolean read GetInterlaced write SetInterlaced;
    property ColorMap: TGIFColorMap read FColorMap;
    property ActiveColorMap: TGIFColorMap read GetActiveColorMap;
    property Data: PChar read FData;
    property DataSize: integer read FDataSize;
    property Extensions: TGIFExtensionList read FExtensions;
    property Version: TGIFVersion read GetVersion;
    property ColorResolution: integer read GetColorResolution;
    property BitsPerPixel: integer read GetBitsPerPixel;
    property Bitmap: TBitmap read GetBitmap write SetBitmap;
    property Mask: HBitmap read FMask;
    property Palette: HPALETTE read GetPalette write SetPalette;
    property Empty: boolean read GetEmpty;
    property Transparent: boolean read FTransparent;
    property GraphicControlExtension: TGIFGraphicControlExtension read FGCE;
    property Pixels[x, y: integer]: BYTE read GetPixel;
    property Scanline[y: integer]: pointer read GetScanline;
  end;

////////////////////////////////////////////////////////////////////////////////
//
//                      TGIFTrailer
//
////////////////////////////////////////////////////////////////////////////////
  TGIFTrailer = class(TGIFItem)
    procedure SaveToStream(Stream: TStream); override;
    procedure LoadFromStream(Stream: TStream); override;
  end;

////////////////////////////////////////////////////////////////////////////////
//
//                      TGIFGraphicControlExtension
//
////////////////////////////////////////////////////////////////////////////////
  // Graphic Control Extension block a.k.a GCE
  TGIFGCERec = packed record
    BlockSize: byte;         { should be 4 }
    PackedFields: Byte;
    DelayTime: Word;         { in centiseconds }
    TransparentColorIndex: Byte;
    Terminator: Byte;
  end;

  TDisposalMethod = (dmNone, dmNoDisposal, dmBackground, dmPrevious);

  TGIFGraphicControlExtension = class(TGIFExtension)
  private
    FGCExtension: TGIFGCERec;
  protected
    function GetExtensionType: TGIFExtensionType; override;
    function GetTransparent: boolean;
    procedure SetTransparent(Value: boolean);
    function GetTransparentColor: TColor;
    procedure SetTransparentColor(Color: TColor);
    function GetTransparentColorIndex: BYTE;
    procedure SetTransparentColorIndex(Value: BYTE);
    function GetDelay: WORD;
    procedure SetDelay(Value: WORD);
    function GetUserInput: boolean;
    procedure SetUserInput(Value: boolean);
    function GetDisposal: TDisposalMethod;
    procedure SetDisposal(Value: TDisposalMethod);

  public
    constructor Create(ASubImage: TGIFSubImage); override;
    destructor Destroy; override;
    procedure SaveToStream(Stream: TStream); override;
    procedure LoadFromStream(Stream: TStream); override;
    property Delay: WORD read GetDelay write SetDelay;
    property Transparent: boolean read GetTransparent write SetTransparent;
    property TransparentColorIndex: BYTE read GetTransparentColorIndex
                                            write SetTransparentColorIndex;
    property TransparentColor: TColor read GetTransparentColor write SetTransparentColor;
    property UserInput: boolean read GetUserInput write SetUserInput;
    property Disposal: TDisposalMethod read GetDisposal write SetDisposal;
  end;

////////////////////////////////////////////////////////////////////////////////
//
//                      TGIFTextExtension
//
////////////////////////////////////////////////////////////////////////////////
  TGIFPlainTextExtensionRec = packed record
    BlockSize: byte;         { should be 12 }
    Left, Top, Width, Height: Word;
    CellWidth, CellHeight: Byte;
    TextFGColorIndex,
    TextBGColorIndex: Byte;
  end;

  TGIFTextExtension = class(TGIFExtension)
  private
    FText		: TStrings;
    FPlainTextExtension	: TGIFPlainTextExtensionRec;
  protected
    function GetExtensionType: TGIFExtensionType; override;
    function GetForegroundColor: TColor;
    procedure SetForegroundColor(Color: TColor);
    function GetBackgroundColor: TColor;
    procedure SetBackgroundColor(Color: TColor);
    function GetBounds(Index: integer): WORD;
    procedure SetBounds(Index: integer; Value: WORD);
    function GetCharWidthHeight(Index: integer): BYTE;
    procedure SetCharWidthHeight(Index: integer; Value: BYTE);
    function GetColorIndex(Index: integer): BYTE;
    procedure SetColorIndex(Index: integer; Value: BYTE);
  public
    constructor Create(ASubImage: TGIFSubImage); override;
    destructor Destroy; override;
    procedure SaveToStream(Stream: TStream); override;
    procedure LoadFromStream(Stream: TStream); override;
    property Left: WORD index 1 read GetBounds write SetBounds;
    property Top: WORD index 2 read GetBounds write SetBounds;
    property GridWidth: WORD index 3 read GetBounds write SetBounds;
    property GridHeight: WORD index 4 read GetBounds write SetBounds;
    property CharWidth: BYTE index 1 read GetCharWidthHeight write SetCharWidthHeight;
    property CharHeight: BYTE index 2 read GetCharWidthHeight write SetCharWidthHeight;
    property ForegroundColorIndex: BYTE index 1 read GetColorIndex write SetColorIndex;
    property ForegroundColor: TColor read GetForegroundColor;
    property BackgroundColorIndex: BYTE  index 2 read GetColorIndex write SetColorIndex;
    property BackgroundColor: TColor read GetBackgroundColor;
    property Text: TStrings read FText write FText;
  end;

////////////////////////////////////////////////////////////////////////////////
//
//                      TGIFCommentExtension
//
////////////////////////////////////////////////////////////////////////////////
  TGIFCommentExtension = class(TGIFExtension)
  private
    FText		: TStrings;
  protected
    function GetExtensionType: TGIFExtensionType; override;
  public
    constructor Create(ASubImage: TGIFSubImage); override;
    destructor Destroy; override;
    procedure SaveToStream(Stream: TStream); override;
    procedure LoadFromStream(Stream: TStream); override;
    property Text: TStrings read FText;
  end;

////////////////////////////////////////////////////////////////////////////////
//
//                      TGIFApplicationExtension
//
////////////////////////////////////////////////////////////////////////////////
  TGIFIdentifierCode = array[0..7] of char;
  TGIFAuthenticationCode = array[0..2] of char;
  TGIFApplicationRec = packed record
    Identifier		: TGIFIdentifierCode;
    Authentication	: TGIFAuthenticationCode;
  end;

  TGIFApplicationExtension = class;
  TGIFAppExtensionClass = class of TGIFApplicationExtension;

  TGIFApplicationExtension = class(TGIFExtension)
  private
    FIdent		: TGIFApplicationRec;
    function GetAuthentication: string;
    function GetIdentifier: string;
  protected
    function GetExtensionType: TGIFExtensionType; override;
    procedure SetAuthentication(const Value: string);
    procedure SetIdentifier(const Value: string);
    procedure SaveData(Stream: TStream); virtual; abstract;
    procedure LoadData(Stream: TStream); virtual; abstract;
  public
    constructor Create(ASubImage: TGIFSubImage); override;
    destructor Destroy; override;
    procedure SaveToStream(Stream: TStream); override;
    procedure LoadFromStream(Stream: TStream); override;
    class procedure RegisterExtension(eIdent: TGIFApplicationRec; eClass: TGIFAppExtensionClass);
    class function FindSubExtension(Stream: TStream): TGIFExtensionClass; override;
    property Identifier: string read GetIdentifier write SetIdentifier;
    property Authentication: string read GetAuthentication write SetAuthentication;
  end;

////////////////////////////////////////////////////////////////////////////////
//
//                      TGIFUnknownAppExtension
//
////////////////////////////////////////////////////////////////////////////////
  TGIFBlock = class(TObject)
  private
    FSize		: BYTE;
    FData		: pointer;
  public
    constructor Create(ASize: integer);
    destructor Destroy; override;
    procedure SaveToStream(Stream: TStream);
    procedure LoadFromStream(Stream: TStream);
    property Size: BYTE read FSize;
    property Data: pointer read FData;
  end;

  TGIFUnknownAppExtension = class(TGIFApplicationExtension)
  private
    FBlocks		: TList;
  protected
    procedure SaveData(Stream: TStream); override;
    procedure LoadData(Stream: TStream); override;
  public
    constructor Create(ASubImage: TGIFSubImage); override;
    destructor Destroy; override;
    property Blocks: TList read FBlocks;
  end;

////////////////////////////////////////////////////////////////////////////////
//
//                      TGIFAppExtNSLoop
//
////////////////////////////////////////////////////////////////////////////////
  TGIFAppExtNSLoop = class(TGIFApplicationExtension)
  private
    FLoops		: WORD;
    FBufferSize		: DWORD;
  protected
    procedure SaveData(Stream: TStream); override;
    procedure LoadData(Stream: TStream); override;
  public
    constructor Create(ASubImage: TGIFSubImage); override;
    property Loops: WORD read FLoops write FLoops;
    property BufferSize: DWORD read FBufferSize write FBufferSize;
  end;

////////////////////////////////////////////////////////////////////////////////
//
//                      TGIFImage
//
////////////////////////////////////////////////////////////////////////////////
  TGIFImageList = class(TGIFList)
  protected
    function GetImage(Index: Integer): TGIFSubImage;
    procedure SetImage(Index: Integer; SubImage: TGIFSubImage);
  public
    procedure LoadFromStream(Stream: TStream; Parent: TObject); override;
    procedure SaveToStream(Stream: TStream); override;
    property SubImages[Index: Integer]: TGIFSubImage read GetImage write SetImage; default;
  end;

  // Compression algorithms
  TGIFCompression =
    (gcLZW,			// Normal LZW compression
     gcRLE			// GIF compatible RLE compression
    );

  // Color reduction methods
  TColorReduction =
    (rmNone,			// Do not perform color reduction
     rmWindows20,		// Reduce to the Windows 20 color system palette
     rmWindows256,		// Reduce to the Windows 256 color halftone palette (Only works in 256 color display mode)
     rmWindowsGray,		// Reduce to the Windows 4 grayscale colors
     rmMonochrome,		// Reduce to a black/white monochrome palette
     rmGrayScale,		// Reduce to a uniform 256 shade grayscale palette
     rmNetscape,		// Reduce to the Netscape 216 color palette
     rmQuantize,		// Reduce to optimal 2^n color palette
     rmQuantizeWindows,		// Reduce to optimal 256 color windows palette
     rmPalette			// Reduce to custom palette
    );
  TDitherMode =
    (dmNearest,			// Nearest color matching w/o error correction
     dmFloydSteinberg,		// Floyd Steinberg Error Diffusion dithering
     dmStucki,			// Stucki Error Diffusion dithering
     dmSierra,			// Sierra Error Diffusion dithering
     dmJaJuNI,			// Jarvis, Judice & Ninke Error Diffusion dithering
     dmSteveArche,		// Stevenson & Arche Error Diffusion dithering
     dmBurkes			// Burkes Error Diffusion dithering
     // dmOrdered,		// Ordered dither
    );

  // Optimization options
  TGIFOptimizeOption =
    (ooCrop,			// Crop animated GIF frames
     ooMerge,			// Merge pixels of same color
     ooCleanup,			// Remove comments and application extensions
     ooColorMap,		// Sort color map by usage and remove unused entries
     ooReduceColors		// Reduce color depth ***NOT IMPLEMENTED***
    );
  TGIFOptimizeOptions = set of TGIFOptimizeOption;

  TGIFDrawOption =
    (goAsync,			// Asyncronous draws (paint in thread)
     goTransparent,		// Transparent draws
     goAnimate,			// Animate draws
     goLoop,			// Loop animations
     goLoopContinously,		// Ignore loop count and loop forever
     goValidateCanvas,		// Validate canvas in threaded paint ***NOT IMPLEMENTED***
     goDirectDraw,		// Draw() directly on canvas
     goClearOnLoop,		// Clear animation on loop
     goTile,			// Tiled display
     goDither,			// Dither to Netscape palette
     goAutoDither		// Only dither on 256 color systems