{
    fpGUI  -  Free Pascal GUI Library
    
    Image I/O interface declarations
    
    Copyright (C) 2000 - 2006 See the file AUTHORS.txt, included in this
    distribution, for details of the copyright.

    See the file COPYING.modifiedLGPL, included in this distribution,
    for details about redistributing fpGUI.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
}


unit ImageIO;

{$IFDEF Debug}
{$ASSERTIONS On}
{$ENDIF}

interface

uses
  SysUtils
  ,Classes
  ,GFXBase
  ;

resourcestring
  SImgOutOfData = 'No more data available for image';
  SImgUnsupportedPixelFormat = 'Unsupported pixel format in image';

type

  EImgError = class(Exception);

  EImgOutOfData = class(EImgError)
  public
    constructor Create;
  end;

  EImgUnsupportedPixelFormat = class(EImgError)
  public
    constructor Create;
  end;


// Image reading

  TImageReaderClass = class of TImageReader;

  TImageReaderState = (irsStart, irsInHeader, irsHeaderRead,
    irsInImage, irsFinished);

  TSegmentEvent = procedure(Sender: TObject; StartY, Height: Integer) of object;

  TImageReader = class
  private
    FState: TImageReaderState;
    { Needed for reading of image data. These values must be initialized by
      the user via SetImageSegmentBuffer }
    FSegmentData: Pointer;
    FSegmentStride: LongWord;
    FSegmentHeight: Integer;
    FSegmentSize: LongWord;		// Size in bytes

    FOnHeader: TNotifyEvent;
    FOnSegment: TSegmentEvent;
    FOnImage: TNotifyEvent;
  protected
    // Image properties, only available after OnHeaderRead event
    FWidth: Integer;
    FHeight: Integer;
    FPixelFormat: TGfxPixelFormat;
    FPaletteSize: Integer;
    FPalette: PGfxColor;
    procedure   HeaderFinished;
    procedure   SegmentFinished(AStartY, AHeight: Integer);
    procedure   ImageFinished;
    procedure   DoProcessHeaderData(AStream: TStream); virtual; abstract;
    function    DoGetImageSegmentStartY(ASegmentHeight: Integer): Integer; virtual; abstract;
    procedure   InitImageReading; virtual;
    procedure   DoProcessImageData(AStream: TStream); virtual; abstract;
  public
    constructor Create; virtual;
    procedure   ProcessHeaderData(AStream: TStream);
    function    GetImageSegmentStartY(ASegmentHeight: Integer): Integer;
    procedure   SetImageSegmentBuffer(AData: Pointer; AStride: LongWord; ASegmentHeight: Integer);
    procedure   ProcessImageData(AStream: TStream);
    property    State: TImageReaderState read FState;
    property    Width: Integer read FWidth;
    property    Height: Integer read FHeight;
    property    PixelFormat: TGfxPixelFormat read FPixelFormat;
    property    PaletteSize: Integer read FPaletteSize;
    property    Palette: PGfxColor read FPalette;
    property    SegmentData: Pointer read FSegmentData;
    property    SegmentStride: LongWord read FSegmentStride;
    property    SegmentHeight: Integer read FSegmentHeight;
    property    SegmentSize: LongWord read FSegmentSize;
    property    OnHeader: TNotifyEvent read FOnHeader write FOnHeader;
    property    OnSegment: TSegmentEvent read FOnSegment write FOnSegment;
    property    OnImage: TNotifyEvent read FOnImage write FOnImage;
  end;


implementation


constructor EImgOutOfData.Create;
begin
  inherited Create(SImgOutOfData);
end;

constructor EImgUnsupportedPixelFormat.Create;
begin
  inherited Create(SImgUnsupportedPixelFormat);
end;

{ TImageReader }

constructor TImageReader.Create;
begin
  inherited Create;
end;

procedure TImageReader.ProcessHeaderData(AStream: TStream);
begin
  ASSERT(FState in [irsStart, irsInHeader]);
  if State = irsStart then
    FState := irsInHeader;
  DoProcessHeaderData(AStream);
end;

function TImageReader.GetImageSegmentStartY(ASegmentHeight: Integer): Integer;
begin
  ASSERT(State in [irsHeaderRead, irsInImage]);
  Result := DoGetImageSegmentStartY(ASegmentHeight);
end;

procedure TImageReader.SetImageSegmentBuffer(AData: Pointer; AStride: LongWord;
  ASegmentHeight: Integer);
begin
  ASSERT(State in [irsHeaderRead, irsInImage]);
  FSegmentData    := AData;
  FSegmentStride  := AStride;
  FSegmentHeight  := ASegmentHeight;
  FSegmentSize    := SegmentStride * SegmentHeight;
end;

procedure TImageReader.ProcessImageData(AStream: TStream);
begin
  if State = irsFinished then
    exit;
  ASSERT(State in [irsHeaderRead, irsInImage]);

  if State = irsHeaderRead then
  begin
    FState := irsInImage;
    InitImageReading;
  end;

  DoProcessImageData(AStream);
end;

procedure TImageReader.HeaderFinished;
begin
  ASSERT(FState = irsInHeader);
  FState := irsHeaderRead;
  if Assigned(OnHeader) then
    OnHeader(Self);
end;

procedure TImageReader.SegmentFinished(AStartY, AHeight: Integer);
begin
  ASSERT(FState = irsInImage);
  if Assigned(OnSegment) then
    OnSegment(Self, AStartY, AHeight);
end;

procedure TImageReader.ImageFinished;
begin
  ASSERT(FState = irsInImage);
  FState := irsFinished;
  if Assigned(OnImage) then
    OnImage(Self);
end;

procedure TImageReader.InitImageReading;
begin
  // Do nothing
end;

end.