// long and slow GIF does not hang the
                                        // system.
                                        // (1000 = 10000 mS = 10 Seconds)

type
  TGIFVersion = (gvUnknown, gv87a, gv89a);
  TGIFVersionRec = array[0..2] of char;

const
  GIFVersions : array[gv87a..gv89a] of TGIFVersionRec = ('87a', '89a');

type
  // TGIFImage mostly throws exceptions of type GIFException
  GIFException = class(EInvalidGraphic);

  // Severity level as indicated in the Warning methods and the OnWarning event
  TGIFSeverity = (gsInfo, gsWarning, gsError);

////////////////////////////////////////////////////////////////////////////////
//
//			Delphi 2.x support
//
////////////////////////////////////////////////////////////////////////////////
{$IFDEF VER9x}
// Delphi 2 doesn't support TBitmap.PixelFormat
{$DEFINE PIXELFORMAT_TOO_SLOW}
type
  // TThreadList from Delphi 3 classes.pas
  TThreadList = class
  private
    FList: TList;
    FLock: TRTLCriticalSection;
  public
    constructor Create;
    destructor Destroy; override;
    procedure Add(Item: Pointer);
    procedure Clear;
    function  LockList: TList;
    procedure Remove(Item: Pointer);
    procedure UnlockList;
  end;

  // From Delphi 3 sysutils.pas
  EOutOfMemory = class(Exception);

  // From Delphi 3 classes.pas
  EOutOfResources = class(EOutOfMemory);

  // From Delphi 3 windows.pas
  PMaxLogPalette = ^TMaxLogPalette;
  TMaxLogPalette = packed record
    palVersion: Word;
    palNumEntries: Word;
    palPalEntry: array [Byte] of TPaletteEntry;
  end; { TMaxLogPalette }

  // From Delphi 3 graphics.pas. Used by the D3 TGraphic class.
  TProgressStage = (psStarting, psRunning, psEnding);
  TProgressEvent = procedure (Sender: TObject; Stage: TProgressStage;
    PercentDone: Byte; RedrawNow: Boolean; const R: TRect; const Msg: string) of object;

  // From Delphi 3 windows.pas
  PRGBTriple = ^TRGBTriple;
{$ENDIF}

////////////////////////////////////////////////////////////////////////////////
//
//			Forward declarations
//
////////////////////////////////////////////////////////////////////////////////
type
  TGIFImage = class;
  TGIFSubImage = class;

////////////////////////////////////////////////////////////////////////////////
//
//			TGIFItem
//
////////////////////////////////////////////////////////////////////////////////
  TGIFItem = class(TPersistent)
  private
    FGIFImage: TGIFImage;
  protected
    function GetVersion: TGIFVersion; virtual;
    procedure Warning(Severity: TGIFSeverity; Message: string); virtual;
  public
    constructor Create(GIFImage: TGIFImage); virtual;

    procedure SaveToStream(Stream: TStream); virtual; abstract;
    procedure LoadFromStream(Stream: TStream); virtual; abstract;
    procedure SaveToFile(const Filename: string); virtual;
    procedure LoadFromFile(const Filename: string); virtual;
    property Version: TGIFVersion read GetVersion;
    property Image: TGIFImage read FGIFImage;
  end;

////////////////////////////////////////////////////////////////////////////////
//
//			TGIFList
//
////////////////////////////////////////////////////////////////////////////////
  TGIFList = class(TPersistent)
  private
    FItems: TList;
    FImage: TGIFImage;
  protected
    function GetItem(Index: Integer): TGIFItem;
    procedure SetItem(Index: Integer; Item: TGIFItem);
    function GetCount: Integer;
    procedure Warning(Severity: TGIFSeverity; Message: string); virtual;
  public
    constructor Create(Image: TGIFImage);
    destructor Destroy; override;

    function Add(Item: TGIFItem): Integer;
    procedure Clear;
    procedure Delete(Index: Integer);
    procedure Exchange(Index1, Index2: Integer);
    function First: TGIFItem;
    function IndexOf(Item: TGIFItem): Integer;
    procedure Insert(Index: Integer; Item: TGIFItem);
    function Last: TGIFItem;
    procedure Move(CurIndex, NewIndex: Integer);
    function Remove(Item: TGIFItem): Integer;
    procedure SaveToStream(Stream: TStream); virtual;
    procedure LoadFromStream(Stream: TStream; Parent: TObject); virtual; abstract;

    property Items[Index: Integer]: TGIFItem read GetItem write SetItem; default;
    property Count: Integer read GetCount;
    property List: TList read FItems;
    property Image: TGIFImage read FImage;
  end;

////////////////////////////////////////////////////////////////////////////////
//
//			TGIFColorMap
//
////////////////////////////////////////////////////////////////////////////////
  // One way to do it:
  //  TBaseColor = (bcRed, bcGreen, bcBlue);
  //  TGIFColor = array[bcRed..bcBlue] of BYTE;
  // Another way:
  TGIFColor = packed record
    Red: byte;
    Green: byte;
    Blue: byte;
  end;

  TColorMap = packed array[0..GIFMaxColors-1] of TGIFColor;
  PColorMap = ^TColorMap;

  TUsageCount = record
    Count		: integer;	// # of pixels using color index
    Index		: integer;	// Color index
  end;
  TColormapHistogram = array[0..255] of TUsageCount;
  TColormapReverse = array[0..255] of byte;

  TGIFColorMap = class(TPersistent)
  private
    FColorMap		: PColorMap;
    FCount		: integer;
    FCapacity		: integer;
    FOptimized		: boolean;
  protected
    function GetColor(Index: integer): TColor;
    procedure SetColor(Index: integer; Value: TColor);
    function GetBitsPerPixel: integer;
    function DoOptimize: boolean;
    procedure SetCapacity(Size: integer);
    procedure Warning(Severity: TGIFSeverity; Message: string); virtual; abstract;
    procedure BuildHistogram(var Histogram: TColormapHistogram); virtual; abstract;
    procedure MapImages(var Map: TColormapReverse); virtual; abstract;

  public
    constructor Create;
    destructor Destroy; override;
    class function Color2RGB(Color: TColor): TGIFColor;
    class function RGB2Color(Color: TGIFColor): TColor;
    procedure SaveToStream(Stream: TStream);
    procedure LoadFromStream(Stream: TStream; Count: integer);
    procedure Assign(Source: TPersistent); override;
    function IndexOf(Color: TColor): integer;
    function Add(Color: TColor): integer;
    function AddUnique(Color: TColor): integer;
    procedure Delete(Index: integer);
    procedure Clear;
    function Optimize: boolean; virtual; abstract;
    procedure Changed; virtual; abstract;
    procedure ImportPalette(Palette: HPalette);
    procedure ImportColorTable(Pal: pointer; Count: integer);
    procedure ImportDIBColors(Handle: HDC);
    procedure ImportColorMap(Map: TColorMap; Count: integer);
    function ExportPalette: HPalette;
    property Colors[Index: integer]: TColor read GetColor write SetColor; default;
    property Data: PColorMap read FColorMap;
    property Count: integer read FCount;
    property Optimized: boolean read FOptimized write FOptimized;
    property BitsPerPixel: integer read GetBitsPerPixel;
  end;

////////////////////////////////////////////////////////////////////////////////
//
//			TGIFHeader
//
////////////////////////////////////////////////////////////////////////////////
  TLogicalScreenDescriptor = packed record
    ScreenWidth: word;              { logical screen width }
    ScreenHeight: word;             { logical screen height }
    PackedFields: byte;             { packed fields }
    BackgroundColorIndex: byte;     { index to global color table }
    AspectRatio: byte;              { actual ratio = (AspectRatio + 15) / 64 }
  end;

  TGIFHeader = class(TGIFItem)
  private
    FLogicalScreenDescriptor: TLogicalScreenDescriptor;
    FColorMap		: TGIFColorMap;
    procedure Prepare;
  protected
    function GetVersion: TGIFVersion; override;
    function GetBackgroundColor: TColor;
    procedure SetBackgroundColor(Color: TColor);
    procedure SetBackgroundColorIndex(Index: BYTE);
    function GetBitsPerPixel: integer;
    function GetColorResolution: integer;
  public
    constructor Create(GIFImage: TGIFImage); override;
    destructor Destroy; override;
    procedure Assign(Source: TPersistent); override;
    procedure SaveToStream(Stream: TStream); override;
    procedure LoadFromStream(Stream: TStream); override;
    procedure Clear;
    property Version: TGIFVersion read GetVersion;
    property Width: WORD read FLogicalScreenDescriptor.ScreenWidth
                         write FLogicalScreenDescriptor.ScreenWidth;
    property Height: WORD read FLogicalScreenDescriptor.ScreenHeight
                          write FLogicalScreenDescriptor.Screenheight;
    property BackgroundColorIndex: BYTE read FLogicalScreenDescriptor.BackgroundColorIndex
                                        write SetBackgroundColorIndex;
    property BackgroundColor: TColor read GetBackgroundColor
                                     write SetBackgroundColor;
    property AspectRatio: BYTE read FLogicalScreenDescriptor.AspectRatio
                               write FLogicalScreenDescriptor.AspectRatio;
    property ColorMap: TGIFColorMap read FColorMap;
    property BitsPerPixel: integer read GetBitsPerPixel;
    property ColorResolution: integer read GetColorResolution;
  end;

////////////////////////////////////////////////////////////////////////////////
//
//                      TGIFExtension
//
////////////////////////////////////////////////////////////////////////////////
  TGIFExtensionType = BYTE;
  TGIFExtension = class;
  TGIFExtensionClass = class of TGIFExtension;

  TGIFGraphicControlExtension = class;

  TGIFExtension = class(TGIFItem)
  private
    FSubImage: TGIFSubImage;
  protected
    function GetExtensionType: TGIFExtensionType; virtual; abstract;
    function GetVersion: TGIFVersion; override;
    function DoReadFromStream(Stream: TStream): TGIFExtensionType;
    class procedure RegisterExtension(elabel: BYTE; eClass: TGIFExtensionClass);
    class function FindExtension(Stream: TStream): TGIFExtensionClass;
    class function FindSubExtension(Stream: TStream): TGIFExtensionClass; virtual;
  public
     // Ignore compiler warning about hiding base class constructor
    constructor Create(ASubImage: TGIFSubImage); {$IFDEF VER12_PLUS} reintroduce; {$ENDIF} virtual;
    destructor Destroy; override;
    procedure SaveToStream(Stream: TStream); override;
    procedure LoadFromStream(Stream: TStream); override;
    property ExtensionType: TGIFExtensionType read GetExtensionType;
    property SubImage: TGIFSubImage read FSubImage;
  end;

////////////////////////////////////////////////////////////////////////////////
//
//			TGIFSubImage
//
////////////////////////////////////////////////////////////////////////////////
  TGIFExtensionList = class(TGIFList)
  protected
    function GetExtension(Index: Integer): TGIFExtension;
    procedure SetExtension(Index: Integer; Extension: TGIFExtension);
  public
    procedure LoadFromStream(Stream: TStream; Parent: TObject); override;
    property Extensions[Index: Integer]: TGIFExtension read GetExtension write SetExtension; default;
  end;

  TImageDescriptor = packed record
    Separator: byte;	{ fixed value of ImageSeparator }
    Left: word;		{ Column in pixels in respect to left edge of logical screen }
    Top: word;		{ row in pixels in respect to top of logical screen }
    Width: word;	{ width of image in pixels }
    Height: word;	{ height of image in pixels }
    PackedFields: byte;	{ Bit fields }
  end;

  TGIFSubImage = class(TGIFItem)
  private
    FBitmap		: TBitmap;
    FMask		: HBitmap;
    FNeedMask		: boolean;
    FLocalPalette	: HPalette;
    FData		: PChar;
    FDataSize		: integer;
    FColorMap		: TGIFColorMap;
    FImageDescriptor	: TImageDescriptor;
    FExtensions		: TGIFExtensionList;
    FTransparent	: boolean;
    FGCE		: TGIFGraphicControlExtension;
    procedure Prepare;
    procedure Compress(Stream: TStream);
    procedure Decompress(Stream: TStream);
  protected
    function GetVersion: TGIFVersion; override;
    function GetInterlaced: boolean;
    procedure SetInterlaced(Value: boolean);
    function GetColorResolution: integer;
    function GetBitsPerPixel: integer;
    procedure AssignTo(Dest: TPersistent); override;
    function DoGetBitmap: TBitmap;
    function DoGetDitherBitmap: TBitmap;
    function GetBitmap: TBitmap;
    procedure SetBitmap(Value: TBitmap);
    procedure FreeMask;
    function GetEmpty: Boolean;
    function GetPalette: HPALETTE;