[[AgustinOrtu]]

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Código Delphi [-]
unit TransparentShape;

interface

uses
  ExtCtrls;

type
  TTransparentShape = class(TShape)
  private
    FTransparent: Boolean;
    procedure SetTransparent(const Value: Boolean);
  published
    property Transparent: Boolean read FTransparent write SetTransparent;
  end;

implementation

uses
  Graphics;

{ TTransparentShape }

procedure TTransparentShape.SetTransparent(const Value: Boolean);
begin
  if FTransparent <> Value then
  begin
    FTransparent := Value;
    if FTransparent then
      Brush.Style := bsClear
    else
      Brush.Style := bsSolid;
  end;
end;

end.

Edito:

Salida -