| Author: | Chen, Xiao |
| Title: | Eliminating harmonics in tiled screens |
| Advisors: | Chan, Chris Y. H. (EIE) |
| Degree: | M.Sc. |
| Year: | 2015 |
| Subject: | Photoengraving -- Halftone process. Image processing -- Digital techniques. Hong Kong Polytechnic University -- Dissertations |
| Department: | Faculty of Engineering |
| Pages: | x, 100 leaves : illustrations ; 30 cm |
| Language: | English |
| Abstract: | Halftoning is a process of transforming a continuous tone image to a bi-level image. Conventional frequency modulation halftoning algorithms are generally classified into three categories include: screening, error diffusion and iterative methods. Among them, screening is of the lowest realization complexity as it is carried out by thresholding the pixel values in an image with a pre-defined threshold matrix called screen. In general, in order to increase the flexibility, a small screen of fixed size, which is referred to as tile screen, is developed in advance. Whenever necessary, a screen of desirable size is constructed on line to halftone a given image by tiling the developed tile screens.Conventional tiling methods can introduce blocking artifacts to a screening output if the spatial inter-correlation among adjacent tile screens in a constructed screen is not taken into account when developing the tile screens. These blocking artifacts appear as some abrupt transition across the boundary of two blocks in a screening output. Conventional tiling methods can also introduce some harmonic distortion to the screening output when the constructed screen is periodic. This work addresses these issues and proposes some solutions to remove the blocking artifacts and the harmonic distortion that are commonly found in the outputs of conventional screening algorithms. |
| Rights: | All rights reserved |
| Access: | restricted access |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| b28110559.pdf | For All Users (off-campus access for PolyU Staff & Students only) | 3.57 MB | Adobe PDF | View/Open |
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