Krahn was born in Santiago de Chile. His first drawings date from the period between 1952 and 1956, but his professional career, as a cartoonist and artist, did not start until 1961, in New York City, where he lived until 1969; during this time he had his cartoons published in magazines such as "Esquire", "The New Yorker", "The Atlantic" (then "The Atlantic Monthly") and "The Reporter" He would return to his country in 1971, where he worked for the magazine "Ercilla", but in 1973 had to move to Sitges, Spain, in order to escape from the September 11 coup d'état. After receiving a fellowship from the John Simon Guggenheim Memorial Foundation, he was able to produce his first animated film, "El crimen perfecto", in 1976. In 1984, he began to work for the Barcelona's newspaper "La Vanguardia", where he would publish cartoons and works of animation for the rest of his life.