Fast and accurate binary halftone image resolution increasing by decision-tree learning

Face recognition is done gray or color images. Face recognition can be also done in binary images. Halftone images are binary images having gray shade information. These images are more informative as compared to binary images. Halftone images can be generated from different kernels. The quality of a halftone image depends on the kernel used to generate it. Halftone images can be used to generate human recognizable features for face recognition. The human recognizable features are fed to multiclass SVM classifiers for face recognition. The performance of using different human recognizable features generated from halftone images of different standard kernels is studied. It is found that some of kernels give higher recognition rate than the other. Also, the performance is also dependent on size of the window used for feature extraction. In most cases, the minimum size window 3 × 3 gives higher recognition rate in most of the cases. Of the standard kernels Frankie Siera-3, Stucki kernels give higher recognition rate and of the proposed kernels P2 kernel gives higher recognition rate than other proposed kernels.

Reading performance and visual comfort with scale to grey compared with black-and-white scanned print

The efficient encoding and transmission of information for facsimile communication relies on redundancy in the scanned pixels. Halftone images, especiaily those rendered by high-quality dispersed dot techniques, are busy with alternative black and white pixels and shorter run lengths as compared to text information. Because of this, it is desirable to increase the redundancy and decrease the entropy of those images for efficient encoding and transmission. We propose a novel technique whereby both transmiffing and receiving fax devices have in memory a halftone screen such as the blue noise mask (BNM). The BNM is a halftone screen that produces a visuaily appealing dispersed dot pattern with an unstructured, isotropic pattern. When both the transmitting and receiving fax devices have the same halftone screen in ROM, the problem of halftone image encoding can be reduced to that of transmitting the mean gray value of blocks, or subimages, followed by a sparse halftone error image with increased redundancy and run-lengths compared to the original halftone. Examples show that by using the proposed technique, image entropy can be reduced to 0.2 bits/pixel, and typical run-lengths can increase by a factor of 5. The increase in image quality, combined with increased transmission speed, could add considerably to the utilization and acceptance of halftone fax images.

Data hiding and reversible data hiding research has primarily focused on grayscale and color images, because binary and halftone images are prone to visual distortion caused by a small number of errors in pixel representation. As a result, reversible data hiding is more useful than halftone-based data hiding. This study proposes an investigation of encrypted halftone images based on dual reversible data hiding, which improves the reversibility and security of the image by utilizing a dual cover image. Since halftone images are adequately compressed, they are beneficial in low-channel-bandwidth environments. Hamming code (HC) (7,4) is applied to each block of the halftone image to hide the secret data, and two halftone images are recorded and sent to different receivers at the end of the embedding process. Recipients can use the proposed method and the two marked images to extract the message and recover the cover halftone image. The proposed data hiding method can enhance the quality of the decrypted image by appropriately increasing the block size, and conversely, sufficiently large amounts of data can be hidden by reducing the block size. The experimental results provide evidence of the effectiveness of the proposed method in terms of both image quality and the embedding rate.

Digital image halftoning is treated as an optimization problem to which neural networks provide an efficient parallel solution. An image distortion measure is introduced in which the gray-tone image is approximated by a filtered version of the halftoned image. This distortion measure is minimized by using a near-neighborhood-connected symmetric neural network. The filter used in the distortion measure is estimated on the basis of a training set of gray-tone and bilevel images. This filter is then used for the reconstruction of a gray-tone image from its halftoned version. The above procedure, combined with a postprocessing of the reconstructed image by a nonlinear edge-preserving noise-smoothing filter, provides images of good quality. >

Reproduction couleur par trames irrégulières et semi-régulières

A method is proposed to extract two-dimensional shapes which are similar to a given model shape from a binary image composed of black and white pixels. This extraction problem is equivalent to the problem of determining the position, size, and rotational angle of each similar shape in the binary image. The model shape is transformed with four space transformation parameters, (chi) c, yc, M, and (theta) , and the transformed model shape is overlapped with the binary image. Parameters (chi) c and yc denote xy coordinate values of the center of gravity of the transformed model shape, M is magnification ratio and (theta) is rotational angle. The research goal here is to find out the space transformation parameter set that gives the maximum matching rate between the transformed model shape and a similar shape in the binary image. Genetic algorithm (GA), which is a kind of searching or optimizing algorithm, is employed for this problem. In this method, several virtual living things whose chromosomes represent space transformation parameters are randomly generated in a computer, and they are evolved according to GA. As the result of generation iterations, an evolved individual corresponding to the best space transformation parameter set is obtained. Algorithm of the method and several experimental results are described.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Screening is an important task to convert a continuous-tone image into a binary image with pure black and white pixels. The main contribution of this paper is to show a new algorithm for cluster-dot screening using a local exhaustive search. Our new algorithm generates 2-cluster, 3-cluster, and 4-cluster binary images, in which all dots have at least 2, 3, and 4 pixels, respectively. The key idea of our new screening method is to repeat a local exhaustive search that finds the best binary pattern in small windows of size k × k in a binary image. The experimental results show that the local exhaustive search produces high quality and sharp cluster-dot binary images. We also present an hardware algorithm to accelerate the computation. Our hardware algorithm for a round of the local exhaustive search runs O(k2) clock cycles while the software implementation runs in O(2k2 w2) time, where (2w + 1) × (2w + 1) is the size of Gaussian filter. Thus, from theoretical point of view, our hardware algorithm achieves a speedup factor of O(w2). To show that our hardware algorithm is practically fast, we have implemented it on an FPGA. Our hardware algorithm achieved a speedup factor of up to 229 over the software implementation.

We present general and unified algorithms for lossy/lossless coding of bilevel images. The compression is realized by applying arithmetic coding to conditional probabilities. As in the current JBIG standard the conditioning may be specified by a template. For better compression, the more general free tree may be used. Loss may be introduced in a preprocess on the encoding side to increase compression. The primary algorithm is a rate-distortion controlled greedy flipping of pixels. Though being general, the algorithms are primarily aimed at material containing half-toned images as a supplement to the specialized soft pattern matching techniques that work better for text. Template based refinement coding is applied for lossy-to-lossless refinement. Introducing only a small amount of loss in half-toned test images, compression is increased by up to a factor of four compared with JBIG. Lossy, lossless, and refinement decoding speed and lossless encoding speed are less than a factor of two slower than JBIG. The (de)coding method is proposed as part of JBIG2, an emerging international standard for lossless/lossy compression of bilevel images.

Among the digital halftoning, the error diffusion halftoning gives better subjective quality than other halftoning techniques. But it also makes edges of objects blurred. To overcome the defect, this thesis proposes the modified error diffusion halftoning algorithm to enhance the edges using the spatial perceptual properties of the human visual system. Using the properties that the human eyes perceive not the pixel's luminance itself but the local average luminance and that information that human eyes perceive spatial variation, the proposed method computes information of edge enhancement (IEE). The IEE is added to the quantizer's input pixel and feeds into the halftoning quantizer. The quantizer produces the halftone image having the enhanced edge. Also this thesis proposes the technique that the coefficients of the error diffusion filter are adapted according to the correlation among color components. The computer simulation results show that the proposed method produces finer halftoning images than conventional methods due to the enhanced edges. And the proposed method also preserves similar in edges to original image and reduces some defects such as color impulse and false contours.

Adaptive model-based digital halftoning incorporating image enhancement

The grapevine leaves was analyzed based on fractal geometry, and the study evaluated interdependencies between parameters specific to fractal geometry. The grape varieties considered in the study were represented by Chasselas (Ch), Cabernet Sauvignon (CS), Muscat Hamburg (MH), Muscat Iantarnîi (MI), Muscat Ottonel (MO), Perlă de Csaba (PC), and Victoria (Vi). Fresh leaves were taken from each variety. The leaves were herborized to preserve the integrity of the leaves, and were scanned. Imaging analysis and fractal analysis were used to generate fractal geometry parameters: foreground pixels (FP), fractal dimensions D1 (MEE = 0.5), D2 (MEE = 0.2), BW parameter (black and white pixels), B+BW parameter (black + black and white pixels), W+BW parameter (white + black and white pixels). The descriptive statistical analysis generated the analysis report based on a number of 15 samples for each grapevine variety. Correlation analysis was used to evaluate the interdependence between fractal geometry parameters, for each grape variety. Correlations with different levels of intensity were recorded between the parameters of the fractal geometry, in relation to the vine variety. The values ​​of the correlation coefficient showed some matches and differences of the parameters of the fractal geometry in the seven grape varieties studied. In all cases, a very strong positive correlation was recorded between D1 and D2. Also, a negative correlation was recorded between W+BW and B+BW parameters, but of variable intensity.

All conventional viewing angle switchable liquid crystal displays with pixel division have drawback in light efficiency because the sub-pixel that controls viewing angle does not transmit the incident light at normal direction. In this paper, we propose new viewing angle controllable homogeneously aligned liquid crystal display in which the pixel is composed of red, green, blue, and white pixels. The colored pixels are driven by fringe-field switching and the white pixel is driven by complex field. In wide-viewing angle mode, the liquid crystal (LC) directors in all pixels rotate in plane, contributing to high transmittance. In narrow-viewing angle mode, the LC directors in color pixels rotate in plane for light transmission while the LC directors in white pixel can rotate or tilt upward by simultaneous fringe and vertical electric field. The high tilted LC directors generate light leakage in oblique directions which can be utilized for viewing angle control and also transmission at normal direction for image expression. The proposed device overcomes the long standing problem of transmittance sacrifice in the conventional devices.

An original local-potential morphometric algorithm for information-entropy estimation of the impact of technogenic chemical pollution on forests was proposed. This algorithm is distinguished by a procedure of separation of binary objects—pixel clusters (simply connected, tightly packed sets of white and black pixels)—in satellite photographs by a potential transformation and a procedure of estimation of the changes in the local configuration of pixel clusters by calculating the information entropy for the virtual potential of models of the interaction of pseudoparticles (white and black pixels) of the binary image. This enables one to practically estimate the spatial disturbances in forests by the impact of technogenic chemical pollution using point statistical estimates of the geometric indices of clusters. The proposed algorithm differs from conventional ones that determine the boundaries of binary objects by statistical analysis using co-occurrence matrices or point statistical estimates of the configuration of pixels.

This paper proposes an approach to produce high-quality visual QR codes introducing the concept of function icons (FI)—images embedded into QR code. FI design resembled abstract symbols, like identifiable and memorable smartphone app icons or logos. The embedding visually points to the function of a QR code and therefore is more attractive to the end-user than the traditional QR code. Also, the FI perceptual simplicity increases users’ navigation and accessibility over different media. For optimization, the proposed FI design was altered by pixel size, color, and luminance modification, without affecting the decoding reliably. The contrast between dark and light modules of the FI color tone was determined to a minimum of 70% to enable the code reader’s conversion of the image to grayscale and then segmentation it into black and white pixels. The eye-tracking research on QR codes with implemented icons confirmed the subjective attractiveness evaluation. The technical quality of the proposed design was verified with a QR code readability test. Since more than 95% of examinees successfully recognized the content behind a QR code before scanning and evaluated the design as more attractive than a traditional solution, we demonstrated that our approach produces high-quality results for a variety of FI designs.