Digital Halftoning and the Application to Remote Sensing Images

Most printing devices, such as traditional printing machine and digital printers, are restricted to very few colors. The continuous-tone images should therefore be transformed into binary ones before being printed. The techniques doing this transformation are referred to as digital halftoning. Conventionally, digital halftoning is accomplished by either charging the size of printed dots or changing the relative density of dots on the page. These two methods are analogous to amplitude modulation (AM) or frequency modulation (FM) used in communications. The FM halftoning generally reproduce the details of an image better than AM halftoning. The AM halftoning on the other hand give rise to more homogeneous results when the gray tones of the original image vary slowly. But, these halftoning methods brought problems such as Moire, dot gain, halftone rosette patterns, difficulty of controlling the quality of prints, etc. Now, hybrid halftoning can solve most of the common problems. In this paper we present AM halftoning, FM halftoning and hybrid halftoning. By comparing the three methods of their applications on remote sensing image, we can conclude that hybrid halftoning method is the best way to print remote sensing images.