JPEG is the most common image format in smartphones, computers, or digital cameras. Because numerous JPEG images are easily shared and distributed, there are privacy and security concerns for these images. Hence, the JPEG committee has started a standardization called JPEG privacy and security to resolve these issues. The forgery detection of a JPEG image is the key objective of JPEG privacy and security. In this paper, we propose a novel forgery detection method that is watermark-based, for authenticating JPEG image integrity in the discrete cosine transform (DCT) domain. The proposed method aims at 100% detection accuracy for typical forgeries on JPEG image DCT blocks and to counter a well-known forgery attack called collage attack. For this purpose, the method splits the host image into a group of blocks (GOB). A watermark is generated by collaborating with the neighboring GOBs and is embedded into the GOBs. The experimental results using various sample images show the superiority of the proposed method, exhibiting a negligible visual difference between the original and watermarked JPEG images.

Current electronic warfare (EW) systems, along with the rapid development of information and communication technology, are essential elements in the modern battlefield associated with cyberspace. In this study, an efficient evaluation framework is proposed to assess the effectiveness of various types of EW systems that operate in cyberspace, which is recognized as an indispensable factor affecting modern military operations. The proposed method classifies EW systems into primary and sub-categories according to EWs’ types and identifies items for the measurement of the effectiveness of each EW system by considering the characteristics of cyberspace for evaluating the damage caused by cyberattacks. A scenario with an integrated EW system incorporating two or more different types of EW equipment is appropriately provided to confirm the effectiveness of the proposed framework in cyber electromagnetic warfare. The scenario explicates an example of assessing the effectiveness of EW systems under cyberattacks. Finally, the proposed method is demonstrated sufficiently by assessing the effectiveness of the EW systems using the scenario.

This paper proposes a method for fusing multi-exposed images that can operate on digital cameras or smartphones. The proposed method consists of an automatic exposure bracketing algorithm that determines which exposures to capture and a newly proposed multi-exposure image fusion algorithm. This fusion algorithm attempts to improve the fusion performance on the basis of the recently proposed no-reference image-quality metrics, noting that the exposure change affects the change in the local luminance details, contrast, and colorfulness of a pixel. Experimental results of various sample image sequences show the superiority of the proposed fusion algorithm in terms of both objective and visual evaluations. By using the proposed method, users can capture high-dynamic range images directly on digital cameras or smartphones, without using offline image-processing software.

The Joint Picture Expert Group (JPEG) committee has been standardizing next-generation image compression, called JPEG XL, to meet the specific needs for a responsive web, wide color gamut, and high dynamic range. JPEG XL supports lossy and lossless compression. A variable-sized discrete cosine transform (DCT) block is used for lossy compression. A block partitioning method is regarded as a critical function for the performance of JPEG XL. The current DCT block partitioning method used in JPEG XL is highly dependent on the compression rate and tends to assign small-sized DCT blocks to homogeneously textured regions (HTRs) having similar or regular patterns. We propose a region-adaptive DCT block partitioning method that assigns larger blocks to the HTR. The proposed method identifies the HTRs by using a combined metric employing a sum-modified Laplacian, zero-crossing, and colorfulness metric for measuring the region homogeneity. Objective, subjective, and visual comparison evaluations with the ten images recommended by the JPEG working group were provided to show the improvement in coding performance. The proposed method shows its superiority in terms of the compression efficiency evaluated using six objective metrics, subjective tests with 15 participants, visual comparison improvements in the HTR, and gains in the execution time.

Displays capable of representing high-dynamic range (HDR) images were recently released in the digital consumer electronics market, and consumers have become increasingly interested in HDR images. However, the majority of today's digital imaging devices are still low dynamic range (LDR) using an 8-bit representation for each RGB color components; hence, a backward-compatible HDR image format with an existing LDR-based imaging environment is required. Accordingly, JPEG XT, a new HDR image coding standard providing JPEG backward compatibility was established by the JPEG committee based on the market needs. JPEG XT consists of a base and a residual layer. Both layers are independently encoded by a legacy JPEG encoder. Most importantly, the base layer contains a tone-mapped LDR version of the HDR image for compliance with a legacy JPEG decoder. To date, three profiles have been defined for JPEG XT to encode HDR images, which are represented using floating-point values. This study proposes a new imagecoding scheme that uses a region adaptive prediction method with modified current specifications on JPEG XT Part 7. The proposed method adaptively predicts the HDR pixel value using a different prediction information for each block based on the ratio between the LDR and HDR blocks, which is invariant to the tone-mapping operator, while the existing JPEG XT profiles globally predict the HDR values using an inverse transformation of the LDR values. Experimental results using various sample images show the superiority of the proposed method in terms of objective and visual evaluations.

Recently, the use of virtual reality has been spreading rapidly in many industrial fields, such as games and entertainment, and 360° contents are widely used in various applications of the virtual reality (VR) market. The 360° contents create a virtual space comparable to real scenes. Coupled with the rapid growth of the 360° image/video field, many projection formats have been developed and published. However, the studies which identify the best format for a variety of applications are still limited. Therefore, it is desirable to evaluate the visual quality of the projection formats used in the current market, and the result of the evaluation can be used as an important consideration capable of providing 360° VR service of better quality. Here, we propose a methodology for the subjective test and briefly present ten 360° projection formats used in our experiment. The proposed methodology for the subjective test uses a combination of the Degradation Category Rating (DCR) and Pair Comparison methods. We performed the subjective test with 15 participants for each test step, the experimental set-up for which followed the proposed methodology. The results show that the equirectangular projection format (best known and widely used format in most commercial products) did not give the highest quality. Hybrid equiangular cubemap and equatorial cylindrical projection gave the best quality compared with the other eight formats. Based on the results of the DCR, it is noted that different monitors (size and resolution) do not affect the ranking of 360° image projection formats. Our work presents the ranking of ten published projection formats which is useful for identifying the best format for a future 360° image standard.