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Humans’ perception of visual complexity is often regarded as one of the key principles of aesthetic order, and is intimately related to the physiological, neurological and, possibly, psychological characteristics of the human mind. For these reasons, creating accurate computational models of visual complexity is a demanding task. Building upon on previous work in the field (Forsythe et al., 2011; Machado et al., 2015) we explore the use of Machine Learning techniques to create computational models of visual complexity. For that purpose, we use a dataset composed of 800 visual stimuli divided into five categories, describing each stimulus by 329 features based on edge detection, compression error and Zipf’s law. In an initial stage, a comparative analysis of representative state-of-the-art Machine Learning approaches is performed. Subsequently, we conduct an exhaustive outlier analysis. We analyze the impact of removing the extreme outliers, concluding that Feature Selection Multiple Kernel Learning obtains the best results, yielding an average correlation to humans’ perception of complexity of 0.71 with only twenty-two features. These results outperform the current state-of-the-art, showing the potential of this technique for regression.

Providing the visual complexity of an image in terms of impact or aesthetic preference can be of great applicability in areas such as psychology or marketing. To this end, certain areas such as Computer Vision have focused on identifying features and computational models that allow for satisfactory results. This paper studies the application of recent ML models using input images evaluated by humans and characterized by features related to visual complexity. According to the experiments carried out, it was confirmed that one of these methods, Correlation by Genetic Search (CGS), based on the search for minimum sets of features that maximize the correlation of the model with respect to the input data, predicted human ratings of image visual complexity better than any other model referenced to date in terms of correlation, RMSE or minimum number of features required by the model. In addition, the variability of these terms were studied eliminating images considered as outliers in previous studies, observing the robustness of the method when selecting the most important variables to make the prediction.

The Internet of Things (IoT) is an essential platform for industrial applications since it enables massive systems connecting many IoT devices for analytical data collection. This attribute is responsible for the exponential development in the amount of data created by IoT devices. IoT devices can generate voluminous amounts of data, which may place extraordinary demands on their limited resources, data transfer bandwidths, and cloud storage. Using lightweight IoT data compression techniques is a practical way to deal with these problems. This paper presents adaptable lightweight SZ lossy compression algorithm for IoT devices (SZ4IoT), a lightweight and adjusted version of the SZ lossy compression method. The SZ4IoT is a local (non-distributed) and interpolation-based compressor that can accommodate any sensor data type and can be implemented on microcontrollers with low resources. It operates on univariate and multivariate time series. It was implemented and tested on various devices, including the ESP32, Teensy 4.0, and RP2040, and evaluated on multiple datasets. The experiments of this paper focus on the compression ratio, compression and decompression time, normalized root mean square error (NRMSE), and energy consumption and prove the effectiveness of the proposed approach. The compression ratio outperforms LTC, WQT RLE, and K RLE by two, three, and two times, respectively. The proposed SZ4IoT decreased the consumed energy for the data size 40 KB by 31.4, 29.4, and 27.3% compared with K RLE, LTC, and WQT RLE, respectively. In addition, this paper investigates the impact of stationary versus non-stationary time series datasets on the compression ratio.

Joint communications and sensing functionalities integrated into the same communication network have become increasingly relevant due to the large bandwidth requirements of next-generation wireless communication systems and the impending spectral shortage. While there exist system-level guidelines and waveform design specifications for such systems, an information-theoretic analysis of the absolute performance capabilities of joint sensing and communication systems that take into account practical limitations such as fading has not been addressed in the literature. Motivated by this, we undertake a network information-theoretic analysis of a typical joint communications and sensing system in this paper. Towards this end, we consider a state-dependent fading Gaussian multiple access channel (GMAC) setup with an additive state. The state process is assumed to be independent and identically distributed (i.i.d.) Gaussian, and non-causally available to all the transmitting nodes. The fading gains on the respective links are assumed to be stationary and ergodic and available only at the receiver. In this setting, with no knowledge of fading gains at the transmitters, we are interested in joint message communication and estimation of the state at the receiver to meet a target distortion in the mean-squared error sense. Our main contribution here is a complete characterization of the distortion-rate trade-off region between the communication rates and the state estimation distortion for a two-sender GMAC. Our results show that the optimal strategy is based on static power allocation and involves uncoded transmissions to amplify the state, along with the superposition of the digital message streams using appropriate Gaussian codebooks and dirty paper coding (DPC). This acts as a design directive for realistic systems using joint sensing and transmission in next-generation wireless standards and points to the relative benefits of uncoded communications and joint source-channel coding in such systems.

In this paper we bring forward a new linear method of lossy data compression aiming at effective and efficient utilization of sequential sensor signals. In the course of compression, the filtering and encapsulation are carried out first according to the signal type and the threshold value; second, the linear compression is conducted by comparing the maximum and minimum slopes of the sensor signal; third, the compressed signal is archived into the historical data storage zone for later use. Conversely, the signal is reconstructed by linear interpolation during the decompression process. The test results of a standard sinusoidal signal and a measured dynamic pressure signal show that the proposed method has higher compression ratio and less compression error than the spinning door transformation. It also reveals that this method is suitable for the compression and decompression of various types of sensor signals, especially for those containing massive data, multiple sampling, disturbance and redundancy. [PUBLICATION ABSTRACT]

The existence of error when compressing nonlinear functions into the coefficients of the characteristic model is known to be a key issue in existing characteristic modeling approaches, which is solved in this work by an error-free compression method. We first define a key concept of relevant states with corresponding compressing methods into their coefficients, where the coefficients are continuous and bounded and the compression is error-free. Then, we give the conditions for decoupling characteristic modeling for MIMO systems, and sequentially, we establish characteristic models for nonlinear systems with minimum phase and relative order two as well as the flexible spacecrafts, realizing the equivalence in the characteristic model theory. Finally, we explicitly explain the reasons for normalization in the characteristic model theory.

As camera quality improves and their deployment moves to areas with limited bandwidth, communication bottlenecks can impair real-time constraints of an intelligent transportation systems application, such as video-based real-time pedestrian detection. Video compression reduces the bandwidth requirement to transmit the video which degrades the video quality. As the quality level of the video decreases, it results in the corresponding decreases in the accuracy of the vision-based pedestrian detection model. Furthermore, environmental conditions, such as rain and night-time darkness impact the ability to leverage compression by making it more difficult to maintain high pedestrian detection accuracy. The objective of this study is to develop a real-time error-bounded lossy compression (EBLC) strategy to dynamically change the video compression level depending on different environmental conditions to maintain a high pedestrian detection accuracy. We conduct a case study to show the efficacy of our dynamic EBLC strategy for real-time vision-based pedestrian detection under adverse environmental conditions. Our strategy dynamically selects the lossy compression error tolerances that maintain a high detection accuracy across a representative set of environmental conditions. Analyses reveal that for adverse environmental conditions, our dynamic EBLC strategy increases pedestrian detection accuracy up to 14% and reduces the communication bandwidth up to 14 × compared to the state-of-the-practice. Moreover, we show our dynamic EBLC strategy is independent of pedestrian detection models and environmental conditions allowing other detection models and environmental conditions to be easily incorporated.

This chapter contains sections titled: The Difference Matrix Image Quality Measures Colour Images Experiment and Comparison

In mathematical theory, the discrete cosine transform (DCT) is a lossless orthogonal transformation method which means it outputs exactly the same values of the input after the inverse transformation. However, this is impossible in today’s technology due to the limited capacity of processors in which the maximum value that a number can take is 2 64 - 1 (20-digit number) in a 64-bit register. Since the DCT employs the floating values higher than this precision, there occurs a round-off error which causes a particular loss of information after the inverse transformation. For this reason, the dynamic range of the DCT coefficients should be reduced so that fewer precision digits are employed in the DCT calculations, thereby the round-off error and loss of information are minimized. In this study, conventional DCT equations are improved both in forward and inverse transformation for the sake of high-performance JPEG image compression. The proposed method reduces the dynamic range of the DCT coefficients and provides a low dynamic range DCT (LDR-DCT) by weighting the DCT coefficients with respect to the frequency level. The effectiveness of the proposed LDR-DCT method is experimented mainly by observing the inter-correlation between the compression ratio and the peak signal-to-noise ratio (PSNR) values which is defined as the compression performance (CP). An extensive experimental benchmarking study is done using the publicly available KODAK image dataset in both grayscale and RGB color spaces, separately. According to the experimental results, the average compression performance (CP) is increased up to about 26% in grayscale images and about 17% in RGB images when the quantization factors (21–121) are employed in the quantization process. Additionally, it is observed that there is an average increment in the compression performance (CP) up to about 8% in grayscale images and about 7% in RGB images when the standard IrfanView quantization tables (quality level of 40 to the quality level of 90) are applied. On the other hand, in the absence of quantization when either the quantization factor of 1 or the standard IrfanView quantization table with the quality level of 100 is applied, it is also observed that there is an average increment in the PSNR value up to about 15% in grayscale images and about 33% in RGB images with respect to the average PSNR values of 24 images in the KODAK image dataset. Therefore, though the proposed LDR-DCT method without quantization does not change the compression ratio, it improves the quality of the output obtained after the inverse transform dramatically. In other words, the conventional DCT method should be replaced by the proposed LDR-DCT method in certain areas where compression is not required. Besides, the study claims that the proposed LDR-DCT method can provide at least the same JPEG image quality as the conventional DCT method with much higher compression ratios if the quantization tables are redesigned accordingly.

Lossy compression of remote sensing data has found numerous applications. Several requirements are usually imposed on methods and algorithms to be used. A large compression ratio has to be provided, introduced distortions should not lead to sufficient reduction of classification accuracy, compression has to be realized quickly enough, etc. An additional requirement could be to provide privacy of compressed data. In this paper, we show that these requirements can be easily and effectively realized by compression based on discrete atomic transform (DAT). Three-channel remote sensing (RS) images that are part of multispectral data are used as examples. It is demonstrated that the quality of images compressed by DAT can be varied and controlled by setting maximal absolute deviation. This parameter also strictly relates to more traditional metrics as root mean square error (RMSE) and peak signal-to-noise ratio (PSNR) that can be controlled. It is also shown that there are several variants of DAT having different depths. Their performances are compared from different viewpoints, and the recommendations of transform depth are given. Effects of lossy compression on three-channel image classification using the maximum likelihood (ML) approach are studied. It is shown that the total probability of correct classification remains almost the same for a wide range of distortions introduced by lossy compression, although some variations of correct classification probabilities take place for particular classes depending on peculiarities of feature distributions. Experiments are carried out for multispectral Sentinel images of different complexities.