Thorough Investigation, Improvement, and Data Hiding Watermarking in Digital Halftone Images
Date Issued
2004
Date
2004
Author(s)
Guo, Jing-Ming
DOI
zh-TW
Abstract
Output devices such as halftone printers and palette-based displays are ca-pable of producing only a limited number of colors, whereas the human eye can distinguish around 10 million colors under optimal viewing conditions. Due to the low pass nature of human visual system. The eye perceives only a local spa-tial average of the spots produced by a printing device and is relatively insensi-tive to errors made in high frequencies in an image. Halftoning algorithms therefore aim to preserve these local averages while forcing the errors between the continuous tone image and the halftone image to high frequency regions. Existing halftoning techniques can be broadly classified as ordered dither, error diffusion, and iteration-based halftoning techniques.
The evolution of computer and printer technologies, as well as economics, has been driving the current research. Some issues arise and need to be solved. For example, photographic printed quality, dot gain problem, and halftoning speed.
In this dissertation, first, we propose an iteration-based halftoning, named LMS-halftoning to achieve high quality outputs, which was proved with higher PSNR than error diffusion. Second, a perfect printer model used to overcome the dot gain problem is also proposed here. Finally, a new progress coding scheme applied for order dither images is also included in this work.
The proliferation of digital documents, multimedia processing tools, and the worldwide availability of Internet access have created an ideal medium for copyright fraud and uncontrollable distribution of multimedia content. To deal with this problem, conventional analogue watermarking technology has been adapted to digital media as a tool to achieve copyright protection, ownership trace, authentication, or information hiding. The major issues include robustness, capacity, imperceptible, undeletable, undeletable, and unambiguous. Currently, numerous methods using halftones to embed watermarks have been studied. These techniques can be used for printing security documents such as ID card, currency as well as confidential documents, and prevent from illegal duplication and forgery by further scanning these documents to digital forms.
Some watermarks are fragile and some are robust. Fragile watermarks are designed to be broken easily by common image processing operations and are good for tampering detection and authentication. Robust watermarks are de-signed to survive hostile and/or unintentional attack and are good for copyright control. Generally speaking, data hiding techniques are fragile, and watemark-ing are robust. In this dissertation, we propose several watermarking and data hiding in halftone images that address all the issues described above.
Subjects
數位浮水印技術
數位半色調技術
digital watermarking
digital halftoning
Type
thesis
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