Producing watermarked halftones with multiscale error diffusion

Pao Yue-kong Library Electronic Theses Database

Producing watermarked halftones with multiscale error diffusion

 

Author: Yung, Oi-yan
Title: Producing watermarked halftones with multiscale error diffusion
Degree: M.Sc.
Year: 2006
Subject: Hong Kong Polytechnic University -- Dissertations
Photoengraving -- Halftone process
Color printing -- Data processing
Image processing -- Digital techniques
Department: Dept. of Electronic and Information Engineering
Pages: viii, 73 leaves : ill. ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1958053
URI: http://theses.lib.polyu.edu.hk/handle/200/5482
Abstract: Conventional error diffusion technique (ED) [1] is usually used in producing binary watermarked halftones nowadays. As it processes pixels in a raster scanning order, the output suffers directional hysteresis and it is difficult to hide the watermark in the image by using pixels closed to marked pixels to compensate for the distortion introduced by the watermark. Multiscale Error Diffusion (MED) [2, 3] is an image halftoning technique suggested to overcome some deficiencies in ED [1]. In this dissertation, modifications on watermarked halftone techniques are illustrated. In the two modified processes, MED is used instead of ED in watermarking processes. This dissertation provides watermarked halftones for visual quality comparison and provides a performance analysis under different measurements. Both gray level and constant level images were used as testing images to simulate natural images and industrial testing patterns in the study. Analytical results show that MED is better than ED in eliminating directional hysteresis in watermarked halftones.

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