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{
fpImg - Free Pascal Imaging Library
Copyright (C) 2000 by
Areca Systems GmbH / Sebastian Guenther, sg@freepascal.org
Image I/O interface declarations
See the file COPYING, included in this distribution,
for details about the copyright.
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, 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.
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