Add, change, delete entities procedure

uses DXF, DXFConv, sgConsts;

...

type

  TForm1 = class(TForm)
    Image1: TImage;

...

implementation

procedure TForm1.AddChangeDeleteClick(Sender: TObject);
var
  // a class for reading DXF format
  // Please use a correspond class to read a drawing of other format.
  // For example TsgDWGImage for DWG format, TsgCGMImage for CGM, etc.
  vDrawing: TsgCADDXFImage;
  vLine: TsgDXFLine;
begin
  vDrawing := TsgCADDXFImage.Create;
  vDrawing.LoadFromFile('Entities.dxf');
  // changing color
  vDrawing.CurrentLayout.Entities[1].Color := clBlue;
  vDrawing.CurrentLayout.Entities[1].LineWeight := 2;
  //deleting a circle entity from Entities.dxf
  vDrawing.CurrentLayout.RemoveEntity(vDrawing.CurrentLayout.Entities[2]);
  // add line
  vLine := TsgDXFLine.Create;
  // a point has 3 floating values: x, y, z
  vLine.Point := MakeFPoint(50, 0, 0);
  vLine.Point1 := MakeFPoint(50, 70, 10);
  vLine.LineWeight := 1; // 1 mm
  //adding a line to the drawing database:
  vDrawing.Converter.Loads(vLine);
  //adding a line to the current layout for displaying:
  vDrawing.CurrentLayout.AddEntity(vLine);
  vDrawing.GetExtents; // recalculating the extents of the drawing
  Image1.Canvas.StretchDraw(Rect(0, 0,
    Round(vDrawing.Width * Image1.Height / vDrawing.Height), Image1.Height), vDrawing);
  vDrawing.Free;
end;