Как работать с DWG файлами (AutoCAD)?

Vit: Примечания в коде были на каком-то не то китайском, не то японском языке - удалены!

unit DWGView;
 
interface
 
uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  ExtCtrls;
 
type
  BITMAPINFO256 = record
    bmiHeader: BITMAPINFOHEADER;
    bmiColors: array[0..255] of RGBQUAD;
  end;
 
type
  TNoPreviewEvent = procedure(Sender: TOBject) of object;
  TFileErrorEvent = procedure(Sender: TOBject; DWGName: string) of object;
 
  TDWGView = class(TImage)
  private
    FDWGVersion: string;
    FDWGFile: string;
    FNoPreviewEvent: TNoPreviewEvent;
    FOnFileError: TFileErrorEvent;
    FImage: TImage;
    procedure SetDWGFile(const Value: string);
    procedure SetFImage(const Value: TImage);
  protected
    procedure ReadDWG;
    constructor TDWGView;
  public
  published
    property Image: TImage read FImage write SetFImage;
    property DWGFile: string read FDWGFile write SetDWGFile;
    property DWGVersion: string read FDWGVersion;
    property OnNoPreview: TNoPreviewEvent read FNoPreviewEvent write FNoPreviewEvent;
    property OnFileError: TFileErrorEvent read FOnFileError write FOnFileError;
  end;
 
procedure Register;
 
implementation
 
procedure Register;
begin
  RegisterComponents('Voice', [TDWGView]);
end;
 
procedure TDWGView.ReadDWG;
var
  DWGF: TFileStream; 
  MemF: TMemoryStream; 
  BMPF: TMemoryStream; 
  SentinelF: TMemoryStream;
  bif: BITMAPINFO256; 
  bfh: BITMAPFILEHEADER;
  PosSentinel: LongInt; 
  LenPreview: Integer; 
  RasterPreview: ShortInt; 
  PosBMP: Integer; 
  LenBMP: Integer; 
  IndexPreview: Integer;
  TypePreview: Shortint; 
begin
  if Assigned(FOnFileError) then
    FOnFileError(Self, FDWGFile);
  DWGF := TFileStream.Create(FDWGFile, fmOpenRead);
  BMPF := TMemoryStream.Create;
  MemF := TMemoryStream.Create;
  SentinelF := TMemoryStream.Create;
  try
    SetLength(FDWGVersion, 6);
    DWGF.ReadBuffer(FDWGVersion[1], 6);
    DWGF.Position := 13; 
    DWGF.Read(PosSentinel, 4);
    DWGF.Position := PosSentinel;
    SentinelF.CopyFrom(DWGF, 16); 
    DWGF.Read(LenPreview, 4);
    DWGF.Read(RasterPreview, 1); 
    for IndexPreview := RasterPreview - 1 downto 0 do
    begin
      MemF.Position := 0;
      MemF.CopyFrom(DWGF, 9); 
      MemF.Position := 0;
      MemF.Read(TypePreview, 1); 
      case TypePreview of
        1: ; 
        2:
          begin
            MemF.Position := 1;
            MemF.Read(PosBMP, 4); 
            MemF.Read(LenBMP, 4); 
            DWGF.Position := PosBMP;
            DWGF.ReadBuffer(bif, sizeof(bif));
 
            with bif do
            begin
              bmiColors[0].rgbBlue := 0;
              bmiColors[0].rgbGreen := 0;
              bmiColors[0].rgbRed := 0;
 
              bmiColors[225].rgbBlue := 255;
              bmiColors[225].rgbGreen := 255;
              bmiColors[225].rgbRed := 255;
            end;
 
            bfh.bfType := $4D42;
            bfh.bfSize := LenBMP + sizeof(bfh); 
            bfh.bfReserved1 := 0;
            bfh.bfReserved2 := 0;
            bfh.bfOffBits := 14 + $28 + 1024;
 
            BMPF.Position := 0;
            BMPF.Write(bfh, sizeof(bfh));
            BMPF.WriteBuffer(bif, sizeof(bif));
            BMPF.CopyFrom(DWGF, LenBMP - 1064);
            BMPF.Position := 0;
            Picture.Bitmap.LoadFromStream(BMPF);
          end;
        3: ;
      end;
 
    end;
  finally
    SentinelF.Free;
    MemF.Free;
    DWGF.Free;
    BMPF.Free;
  end;
 
end;
 
procedure TDWGView.SetDWGFile(const Value: string);
begin
  FDWGFile := Value;
  ReadDWG;
end;
 
procedure TDWGView.SetFImage(const Value: TImage);
begin
  FImage := Value;
end;
 
constructor TDWGView.TDWGView;
begin
  //TODO: Add your source code here
  FDWGFile := '';
  FDWGVersion := '';
end;
 
end.

Взято с Delphi Knowledge Base: https://www.baltsoft.com/