Yik-Hing Fung

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This paper studies the restoration of images which are color-quantized with error diffusion. Though there are many reported algorithms proposed for restoring noisy blurred color images and inverse halftoning, restoration of color-quantized images is rarely addressed in the literature especially when the images are color-quantized with halftoning. Direct(More)
In fractal coding technique, an image is encoded by making use of its self-similarity property. The image can be reconstructed with some well-defined contractive mappings based on this property and hence, in theory, the reconstructed image can be of any desirable size by using an initial image of appropriate size during the decoding process. However, in(More)
A fingerprint recognition algorithm based on the wavelet domain features of a fingerprint image is proposed. Critical wavelet coefficients are selected to form a feature vector of the fingerprint. As compared with a recently reported algorithm using a similar approach, the proposed algorithm is superior in terms of both recognition rate and computational(More)
Multiscale error diffusion (MED) is superior to conventional error diffusion algorithms as it can eliminate directional hysteresis completely and possesses a good blue noise characteristic. However, due to its filter design, it is not suitable for systems with poor isolated dot generation and instable dot gain. In this paper, we propose a MED algorithm to(More)
Multiscale error diffusion (MED) is superior to conventional error diffusion algorithms as it can eliminate directional hysteresis completely. However, due to its frame-oriented processing nature, the computational complexity is comparatively high. Furthermore, though theoretically MED can remove directional hysteresis by eliminating predefined scanning(More)
The advance in printing technology makes multilevel halftoning become important as printers can now print inks of different intensities. This letter presents a multilevel halftoning algorithm that is based on multiscale error diffusion. This algorithm takes care of the constrained pixels before handling the unconstrained pixels and diffuses errors with a(More)
A good halftoning output should bear a blue noise characteristic contributed by isotropically-distributed isolated dots. Multiscale error diffusion (MED) algorithms try to achieve this by exploiting radially symmetric and noncausal error diffusion filters to guarantee spatial homogeneity. In this brief, an optimized diffusion filter is suggested to make the(More)