Halftoning Using Ink-Jet: Part I. Algorithm of Discretization

Main features of ink-jet printers - fixed dot size - overlap of dots on paper - fixed addressability of dots on page - restricting selection of algorithm for halftoning with ink-jet machines. This size of dots is big enough to prevent usage of complete picture of elements (orthographic tone fonts) because of high spatial resolution of eye in B/W. Ordered dither methods produce blurred edges and create false textures. Error diffusion algorithm was selected as more superior from the rest of half-toning methods. Main attention was paid to break false textures in reproduction of large areas of the same level by additional pseudo-randomization of thresholds. Fresnel zone plate images were used to study frequency responses of the algorithm and the appropriate balance between randomization and high frequency reproduction was found. Error diffusion algorithm was selected as more superior from the rest of half-toning methods. Main attention was paid to break false textures in reproduction of large areas of the same level by additional pseudo-randomization of thresholds. Fresnel zone plate images were used to study frequency responses of the algorithm and the appropriate balance between randomization and high frequency reproduction was found.