A device for applying flowable material to a substratum rotated about an axis of rotation, in accordance with image data stored as pixels or vectors of a Cartesian coordinate grid in a first memory, has at least one printing head for discharging material drops of the flowable material, and is arranged above the substratum, and a controller for positioning the substratum in relation to the printing head and controlling the discharge of the material drops. In a second memory, special polar coordinate grid points arranged on circular lines and on first rays having a first angular distance and, in the direction of origin, on further rays having an angular distance from each other that is greater than the first angular distance are stored. The special polar coordinate grid points are transformed into coordinates of the Cartesian coordinate system, and are compared with the pixels of the image file.