Load the CAD file procedure

uses DWG, DXF, CGM, HPGL2, SVG;

...

type

  TForm1 = class(TForm)

    Image1: TImage;

...

implementation

procedure TForm1.LoadFileClick(Sender: TObject);
var
  // Delphi TPicture object works with CAD files when
  // CAD Import VCL libraries are in uses section
  vPicture: TPicture;
  // for calculation of drawing visualization rectangle
  vRect: TRect;
  vRatioW, vRatioH: double;
begin
  vPicture := TPicture.Create;
  if OpenPictureDialog1.Execute then
    vPicture.LoadFromFile(OpenPictureDialog1.FileName);
  //calculating the drawing visualization rectangle
  //  vPicture.Graphic stores CAD graphic if you open DWG, DXF, PLT or
  // other supported CAD extension
  vRect := Image1.ClientRect;
  vRatioW := vRect.Right/vPicture.Graphic.Width;
  vRatioH := vRect.Bottom/vPicture.Graphic.Height;
  if (vRatioW > vRatioH) then
    vRect.Right := Round(vPicture.Graphic.Width * vRatioH)
  else
    vRect.Bottom := round(vPicture.Graphic.Height * vRatioW);
  Image1.Canvas.StretchDraw(vRect, vPicture.Graphic);
end;