Artist Asger Jorn's most famous work was vandalized at Museum Jorn in April last year, when Ibi-Pippi Orup Hedegaard pasted a picture of herself there and signed the painting with a black felt-tip pen.
A "double modification" and a continuation in Jorn's artistic spirit, the perpetrator later claimed in a post on Facebook.
The punishment is one and a half years in prison and the equivalent of 2.9 million Swedish kroner in damages.
The District Court in Viborg considers that the vandalism was unusually severe.
The restoration of the work, which museum director Jacob Thage called "a national treasure", took almost six months.
Ibi-Pippi Orup Hedegaard has explained that she wanted to create a debate about artistic ownership of images, because Asger Jorn himself started from a landscape painting that he bought at a flea market and then painted an expressionist duckling on.
Nowadays, the work hangs behind protective glass.
In the clip: See when the painting is vandalized, from Kulturnyheterna May 2022.