Un ejemplo de utilización completa sería:
Código Delphi
[-]
procedure TFMPruebas.BBase64Click(Sender: TObject);
var
strJSON, strBase64 : string;
StreamOrigen, AMemoryStream : TStream;
QR : TImage;
begin
inherited;
strJSON := '{"ver":1,"fecha":"2020-10-13","cuit":30000000007,"ptoVta":10,"tipoCmp":1,"nroCmp":94,"importe":12100,"moneda":"DOL","ctz":65," tipoDocRec":80,"nroDocRec":20000000001,"tipoCodAut":"E","codAut":70417054367476}';
StreamOrigen := TStringStream.Create(strJSON);
AMemoryStream := TMemoryStream.Create;
QR := TImage.Create(Self);
try
AMemoryStream.CopyFrom(StreamOrigen, StreamOrigen.Size);
StreamToStrB64(TMemoryStream(AMemoryStream), strBase64);
CrearCodigoQR(QR.Picture.Bitmap, strBase64, 3);
finally
StreamOrigen.Free;
AMemoryStream.Free;
QR.Free;
end;
end;