The airbrush was invented in the late nineteenth century, but it was not until the mid twentieth century that it became a popular tool in painting. It is a small, hand-held instrument connected to a canister of compressed air that sprays paint in a controlled way. Pioneers of airbrushing were the graphic illustrators George Petty and Alberto Vargas (or Varga) in the 1930s and 1940s. Later, Pop artist James Rosenquist used it to evoke the qualities of advertising. In Britain, the artist Barrie Cook became one of the leading practioners to use airbrushing. Today, it is the sci-fi artist H. K. Giger who is most commonly associated with the medium. There is also an airbrushing computer program, invented in the early 1980s, which creates a similar effect in a digital format.