One of the most famous drawings by Leonardo da Vinci is a self-portrait in
red chalk, where he looks quite old. In fact, there is a sketch in one of his
notebooks, partially covered by written notes, that can be a self-portrait of
the artist when he was young. The use of image processing, to remove the
handwritten text and improve the image, allows a comparison of the two
portraits.Comment: Image processing, digital restoration, Leonardo da Vinc