In some Western countries, artists sit on the kerb of public footpaths and paint pictures of those who wish…

In some Western countries, artists sit on the kerb of public footpaths and paint pictures of those who wish to get their portraits drawn for a fee. They do so by asking their customers to pose for them, and then carefully observe their faces in order to paint their portraits. Is it permissible for a woman with hijãb to ask the artist to draw her picture?