Part Of Pixels Research Articles

Wide-Viewing-Angle Integral Imaging System with Full-Effective-Pixels Elemental Image Array.

There exists a defect of the narrow viewing angle in the conventional integral imaging system. One reason for this is that only partial pixels of each elemental image contribute to the viewing angle and the others cause image flips. In this paper, a wide-viewing-angle integral imaging system with a full-effective-pixels elemental image array (FEP-EIA) was proposed. The correspondence between viewpoints and pixel coordinates within the elemental image array was built up, and effective pixel blocks and pixels leading to flipping images were deduced. Then, a pixel replacement method was proposed to generate the FEP-EIAs, which adapt to different viewing distances. As a result, the viewing angle of the proposed integral imaging system was effectively extended through the replacement of the pixels, which caused the image flips. Experiment results demonstrated that wide viewing angles are available for the proposed integral imaging system regardless of the viewing distances.

Recognition and segmentation of complex texture images based on superpixel algorithm and deep learning

Recognizing and segmenting complex texture images such as materials is of great significance to industrial design and production. Due to the lack of sufficient training samples and fuzzy boundaries in material images, it is difficult to segment material images by using deep learning methods. In material images, the pixels of each phase have a high degree of similarity, so if partial pixels’ features in each phase are learned, the whole phase can be recognized. In this paper, we propose a method based on deep learning for recognizing and segmenting material images with complex textures. Firstly, the simple linear iterative cluster(SLIC) algorithm is used to obtain different numbers of superpixels which are a group of pixels with similar texture features. Then we extract the largest inscribed rectangular block in each superpixel. Next, put these rectangular blocks into the classical convolutional neural network(CNN)—DenseNet to recognize them. To retain the key texture features and reduce redundant information, we increase the receptive field in the key layers of DenseNet. In addition, due to the uneven distribution of phases in the material images, we improve focal loss to fit the material image. We make extensive comparative and ablation experiments to confirm the effectiveness of our method.

Progressive [formula omitted] secret image sharing schemes based on Boolean operations and covering codes

(k,n) progressive secret image sharing (PSIS) schemes were discussed frequently in recent years. A (k,n) PSIS scheme consists of sharing phase and reconstruction phase. During sharing phase, a secret image is encrypted into n image-shadows; while during reconstruction phase, k to n image-shadows can progressively recover the image; fewer than k image-shadows get no information on the image. Most previous PSIS schemes can be divided into two categories, polynomial based PSIS schemes and visual cryptography based PSIS schemes. Polynomial based schemes can recover high quality image with complicated cryptographic computations; visual cryptography based PSIS schemes can reconstruct image using human visual system without any cryptographic computation, however, the size of image shadow expands largely from the image and the recovered image is quality-distortion. The motivation of this work is to solving the problems in existing PSIS schemes. Thus, in this paper, we adopt three Boolean operations: bit-level XOR, COV(1,7,3) from (7,4) Hamming code and COV(2,8,4) from (8,4) shortened Hamming code to propose three (k,n) PSIS schemes. In our schemes, k to n image-shadows can decrypt randomly partial pixels on entire image, and reconstruct image progressively. Comparing with previous PSIS schemes, our schemes has smaller image-shadow size and higher quality of recovered image than visual cryptography based PSIS schemes. On the other hand, our schemes has much more efficient operations in sharing procedure and image reconstruction procedure than polynomial based PSIS schemes.

Effective reversible data hiding in encrypted image with privacy protection for image content

In this paper, we propose a novel reversible data hiding scheme in encrypted image. The content owner encrypts the original image with the encryption key to achieve privacy protection for image content, and then, each block of the encrypted image is embedded with one secret bit by the data hider using the data-hiding key. Through the elaborate selection for partial pixels to be flipped, data hiding process only conducts slighter modifications to each block, which leads to significant improvement of visual quality for the decrypted image. The receiver can easily decrypt the marked, encrypted image using the encryption key, and then, through the data-hiding key and an adaptive evaluation function of smoothness characteristic along the isophote direction, secret data can be extracted from the decrypted image, and the original image can further be recovered successfully. Experimental results demonstrate the effectiveness of the proposed scheme.

Natural three-dimensional display with smooth motion parallax using active partially pixelated masks

A set of active partially pixelated masks is designed to pick up appropriate images from a large number serial pictures or a three-dimensional computer numerical model for the natural three-dimensional display with smooth motion parallax. To realize the smooth three-dimensional display without view zone jumping, each subpixel at the boundary in the pixelated mask is subdivided into partial pixels. Each active partially pixelated mask can periodically shift according to the design requirement. With active partially pixelated masks in the liquid crystal panel combining with a precision lenticular lens array, the three-dimensional display with 500 views from captured serial pictures and 1200 views from a computer numerical model is demonstrated in 56° viewing angle, which is functionally equivalent to the holographic stereogram. The displayed depth is more than 40cm. The light intensity ripple with 18 active partially pixelated masks is decreased to 0.9% in the viewing zone. The screen size is 50.7cm×28.5cm.

Multiscale Fractal Descriptors and Polynomial Classifier for Partial Pixels Identification in Regions of Interest of Mammographic Images

Computer systems are used to support breast cancer diagnosis, with decisions taken from measurements carried out in regions of interest (ROIs). We show that support decisions obtained from square or rectangular ROIs can to include background regions with different behavior of healthy or diseased tissues. In this study, the background regions were identified as Partial Pixels (PP), obtained with a multilevel method of segmentation based on maximum entropy. The behaviors of healthy, diseased and partial tissues were quantified by fractal dimension and multiscale lacunarity, calculated through signatures of textures. The separability of groups was achieved using a polynomial classifier. The polynomials have powerful approximation properties as classifiers to treat characteristics linearly separable or not. This proposed method allowed quantifying the ROIs investigated and demonstrated that different behaviors are obtained, with distinctions of 90% for images obtained in the Cranio-caudal (CC) and Mediolateral Oblique (MLO) views.

Information Theoretic Weighting for Robust Star Centroiding

A statistical methodology for the global and local analysis of star tracker image content is presented that is based on the A-Contrario framework. A level set analysis using this methodology effectively weights signals with a confidence interval based on the information content. Globally this analysis can represent the non-planar noise floor associated with the sky background. Locally, this analysis can automatically define the annulus that represents the partial pixels associated with the boundary between signal and noise. The performance of centroiding with information theoretic weighting is evaluated compared to traditional thresholding methods for simulated and real star tracker images.

Characteristic analysis of Otsu threshold and its applications

This paper proves that Otsu threshold is equal to the average of the mean levels of two classes partitioned by this threshold. Therefore, when the within-class variances of two classes are different, the threshold biases toward the class with larger variance. As a result, partial pixels belonging to this class will be misclassified into the other class with smaller variance. To address this problem and based on the analysis of Otsu threshold, this paper proposes an improved Otsu algorithm that constrains the search range of gray levels. Experimental results demonstrate the superiority of new algorithm compared with Otsu method.

Removal of salt-and-pepper noise based on compressed sensing

An image restoration method for removing salt-and-pepper noise is proposed. The key point of the method is the sparsity used to reconstruct the whole image based on partial noise-free pixels. Experimental results demonstrate the better performance of the proposed method compared to the existing modified median-type filters.

Empirically Based Printer Model of Halftone Structure

A number of image quality metrics depend on the structure of the printed halftone dot. The dot structure depends in a complex way on the individual processes in a xerographic marking engine. This paper describes a model which reduces this complexity into a set of key parameters. The parameters are derived from microscopic optical measurements of the dot structure in the halftoned print on paper. The halftone printer model is written specifically for a single color separation, fast calculation, and physically based parameters. Given a fill pattern and a threshold value, it calculates the local image density as a function of position in a halftone supercell. The model has been applied to the appearance of partial pixels and to high frequency banding caused by irregularities in the raster optical scanner (ROS) beam spacing.

Evaluation of CsI(Tl)-PIN diode array tiling schemes

Methods of tiling scintillator-photodiode detector arrays were investigated. Si photodiodes coupled to CsI(Tl) scintillation crystals are being considered for high-resolution (/spl sim/1 mm) gamma-ray imaging. Large area (/spl sim/200 cm/sup 2/) detectors can be assembled by tiling together modular arrays. The goal of the tiling schemes was to maintain uniform pixel pitch and detector performance across the seam where the arrays join. The perimeter of the array has an insensitive area that can be an appreciable fraction of a pixel size when using 1 mm pixels. One tiling scheme used smaller pixels at the edge of the arrays to compensate for this insensitive area (partial PIN method). A second approach used a scintillator light-sharing technique to cover the insensitive area (segmented method). The partial pixel method resulted in worse energy resolution and sensitivity in the partial pixels compared to the full pixels (20% and 30% FWHM at 140 keV for edge and corner pixels, respectively, versus 12% in full pixels, with relative corner pixel sensitivity of /spl sim/50%), but successfully maintained spatial resolution and pixel pitch. The segmented crystal light-sharing method demonstrated 17%-20% FWHM energy resolution (at 140 keV) in the edge pixels, /spl sim/85% relative sensitivity, and provided good pixel identification (i.e., good spatial resolution). However, the segmented crystal method is considerably more complex to implement, compared with the partial pixel method.

面端エッジ検出フィルタを用いた部分画素抽出による画像照合

Reduction of the number of pixels for image template matching is useful to perform the high speed matching. This paper describes methods to extract partial pixels in a template image for high speed template matching and evaluates the reliabilities of the matching results by the methods. The 15 types of methods to extract partial pixels were applied to the 50 kinds of experimental images and all matching results were evaluated. The filter to detect the maximum strength of the plane edges to the eight directions recorded the higher SN ratios in the matching results. On the other hand, it was found that the conventional method that extracts pixels at a constant interval was not useful for many experimental images.

Partial pixels: a three-dimensional diffractive display architecture

We describe in detail the partial pixel architecture that permits the realization of three-dimensional (3-D) displays that are functionally equivalent to a real-time holographic stereogram. This architecture permits the simultaneous presentation of multiple stereoscopic images so that motion parallax is discernible in the resultant 3-D scene. The key innovation of the architecture is that each pixel is subdivided into partial pixels, which in turn can be implemented as individual diffraction gratings. We describe a static display that exhibits a 3-D image with one-dimensional motion parallax, thereby demonstrating key features of the architecture. A variety of partial pixel implementations are discussed that can operate at video frame rates. These include voltage-controlled liquid crystal gratings and binary optic gratings integrated with conventional liquid crystal amplitude modulators. In addition, we describe how the partial pixel architecture can be generalized for the implementation of full-color displays and displays having two-dimensional motion parallax.