[1] He was born in Koblenz-Ehrenbreitstein, the son of Franz Josef Mähler and Anna Johanna, née Vacano.
He first served an apprenticeship in Dresden with Anton Graff to become a painter and later on, he continued with his studies at the Academy of Fine Arts Vienna.
He painted his first portrait of Beethoven, which shows three quarters of the composer's body in an Arcadian landscape, holding a lyre-guitar in his hand.
In the 19th century, this illustration – one of just a few depictions of Beethoven when he was young – mainly became famous due to a lithograph by Josef Kriehuber.
As written in the Allgemeine Musikzeitung (General music journal) in August 1815, "all of them distinguish themselves in a most creditable way through the effectual brush stroke, the descriptive resemblance and the distinctive expression of their soul".