A picture element data generating method comprises the steps of extracting a noticeable pixel and a plurality of reference pixels from image data, the reference pixels being adjacent to the noticeable pixel; and generating a pixel positioned within a minimum polygon which is formed so as to include the noticeable pixel and the reference pixels as vertexes thereof or include the reference pixels as vertexes and the noticeable pixel on a side thereof. A level of the pixel being calculated by use of levels of the noticeable and reference pixels which are weighed.