Gantner was born in 1948 in Seoul, South Korea. He was instantaneously attracted to color and form. By the age of 12 he was attempting to recreate his universe through the medium of paint. Gantner is primarily a self-taught artist. His passion for the Impressionists and the Post-Impressionists was responsible for his move to France. This allowed him to freely study their work and to explore their universe. The majority of Gantner's paintings are set in Provence and the Midi.

The artist's fascination with quaint mountain villages with their narrow, winding streets becomes a perfect vehicle for the true subject of his work's solitude. Gantner's paintings are visual records of absence.

This theme is reinforced through the artist's use of confined luminous and shadowed spaces that are defined and contained by vertical walls of stone. Even when the painting is not of a narrow village street, solitude and absence are still present. Trained in the Impressionist vein, Gantner has resolved the age-old Poussiniste-Rubeniste conflict by combining the strengths and qualities of line with color. This is apparent in Gantner's return to Giverny to repaint Monet's Japanese bridge and waterlilies. The spontaneous quality that defined the impressionism of Monet has given way to a painted drawing that is a controlled application of color structured within a strong linear composition.