抄録
The AM (halftone) screening technology used widely up till now in the printing industry expresses gradations by adjusting dot size. In recent years, CTP has been introduced and with advances in printing technology including screening methods, printed matter with high image quality, high resolution, and high added value has become the norm. Advances in FM screening technology are regarded with particular interest due to its high image quality and stable print quality. FM screening technology represented by dithering and error diffusion that gradations are expressed using random dot arrangements. Consequently, the moirë and rosette patterns characteristic of AM screening do not arise, but it nevertheless has a rough granular quality. A further problem is that, since the dots are small, it must be changed significantly for application in conventional printing environments with stringent printability conditions. In this research, we propose a new hybrid screening method combining the advantages of both conventional FM screening and halftone. Specifically, we carried out binarization to convert the multi-level grayscale value pixels of the grayscale image to the number of black pixels of the binary image with halftone cells using halftone dots, then prepared a different FM image from the conventional FM screening image with arrangement of the black pixels using a chessboard pixel arrangement and random numbers. In addition, the isolated small black pixels which are evenly distributed in conventional FM images were consolidated into cluster patterns by a series of pattern conversion processes. Finally, we reduced roughness and applied image quality correction to achieve a new hybrid screening method with improved image quality.
