This paper proposes an efficient reversible compression technique that utilizes the characteristics of topographic map images, which normally consist of limited number of colors. Firstly, each pixel's color value is converted from a standard RGB code to an index number. This is called an Indexed Color System. Secondly, optimized Run-Length Coding (ORLC) is developed from basic Run-Length Coding to eliminate spatial redundancy by grouping the adjacent pixels that have identical indices into a single code. These data are finally developed from the fixed length codes and saved in the variable codes with Huffman coding. It has been proven by the experiments that the data size is smaller than with Winzip compression technique 29—44%: while the process time depends on the scanned image resolution and the efficiency of CPU and RAM.
In the mono-component non-magnetic toner system, proper toner charging and mass transfer are important factors to get fine quality images. In this report, we focus on the charging mechanism in the toner developing system. By using a microscopic current measurement technique, the dynamics of toner charging were investigated. It was found that a current was observed to flow through each part (i.e. the development roller, blade, and supply roller) during the roller rotation with toner attached on its surface. Development rollers that have various surface properties were prepared for this study. Toner charging has strong relationship to the magnitude of ionization potential of blade, toner and development roller. It was concluded that the microscopic current measurement technique is useful for discussing toner charging and toner transfer mechanism.
A new metric, blockwise distortion measure for multispectral images (BDMM), is proposed to evaluate the quality of compressed multispectral images. The metric is based on blockwise distortion measures which are computed between the original multispectral image and the compressed/reconstructed multispectral image. The computed measures between the two images are adapted to a visual scale which is based on the mean opinion score (MOS). The visual scale is obtained from visual comparison of spectral bands of multispectral images. Two methods were used for matching the MOS-values with the measures computed from the images: the nonlinear weighting using the neural network gave better matching than the linear model by optimization. The measure with empirically defined parameter values is given. The results from the new metric are compared to mean-square-error (MSE) based measures, to blockwise distortion measure, and to picture quality scale for grayscale images. Multiwavelets, the principal component analysis, and JPEG are used in the compression of the multispectral images. The metric can be used with different multispectral images and with different compression methods.
A small convolution mask for image restoration is obtained by passing a specially defined test pattern through the degradation filter. The generated test matrix is then pseudo-inversed to give a least square operator. The operator can be decomposed into a bank of singular value sub-filters. Regularization based on truncated SVD and an optimization procedure is introduced to suppress high order SV components. Unlike the methods described in some previous works, only small sized matrices are involved in the computation. The size of matrices under consideration is related only to the sizes of the degradation and restoration operators respectively, and independent of the image size. This makes the technique suitable for software and hardware implementation.
A new method for inserting invisible watermark into a digital image is described, which uses two layers of orthogonal transforms including block DCT and two dimensional Fourier transform, pseudorandom data shuffling and a dither modulation technique. Neither the original host image nor the inserted data string is needed in detection and extraction of the watermark. Numerical experiments show that watermark embedded in the proposed way is sufficiently transparent, and robust against various attacks. A desired tradeoff between invisibility, robustness, and information embedding capacity can be achieved by appropriately choosing the system parameters and the candidate coefficients for embedding.
In this paper, an image de-noising method based on integer wavelet transform and Donoho's nonlinear wavelet thresholding is presented to post-process reconstructed image after compressing. If the image signal has abundant high-frequency details in wavelet domain, the estimation of threshold value in Donoho's de-noising algorithm will be interfered and some high-frequency information of the signal will be lost. So this paper incorporates adaptability into lifting algorithm to make distribution of image signal energy more concentrative, so that the threshold value can be depressed and then the PSNR of image is improved. The paper also combines redundant wavelet transform with adaptive wavelet transform to improve the de-noising performance of Donoho's thresholding algorithm.
This paper proposes that to achieve the high quality color print goal requires increasing the resolution of current Electrophotographic (EP) printers from 600 dots per inch (dpi) to true 1200 dpi as a minimum and preferably higher. The central point of the argument is that in order to take advantage of the stability of digital printing and reduce the sensitivity to noise arising from photoreceptor non-uniformity and developer noise, the edges of the photodischarged halftone pixels must be sharpened. Since the light spots are diffraction limited, sharper pixel voltage edges can only be achieved by using higher resolution spots. Increasing resolution has consequences on the entire EP system, but only two substems are considered here: the laser scanning imaging system and the photoreceptor. Two laser technologies are discussed for higher resolution imaging systems, VCELs and blue (violet) lasers. A key OPC limitation to higher resolution is coulomb blooming caused by thick CTLs of current photoreceptors. To take full advantage of higher resolution requires photoreceptors with top surface generation. The key technology to enable this is single layer photoreceptor design.
Pigmented inkjet inks for printing on cotton, polyester, cotton/polyester blend, and silk were prepared by changing types of resin. The resins were investigated in terms of emulsion stability, water uptake, and Young’s Modulus of the resin films. The pigments were incorporated in the emulsions and other compositions in the inkjet ink also gave colored inks. Viscosity, surface tension, and pH of the inks were measured and adjusted to meet the requirement of the printer. The four-color inks were printed on nontreated fabrics by a piezo-driven inkjet printer. The printed fabrics were investigated for the depth of ink penetration, stiffness, and crockfastness. This research elucidates the relationship between hydrophilic/hydrophobic properties of the fabrics, which affects the quality of prints.