Digital image enhancement with DStretch®: Is complexity always necessary for efficiency?

Characteristics of the lesions in digital mammography images will be more clear after image enhancement, which can increase the detection rate of early breast cancer. This paper proposes a modified unsharp masking approach based on an improved high-pass filter. Experimental result of digital mammography image enhancement proves that the proposed method can effectively extrude the edges of lesions and at the same time can suppress the noises in uniform background areas.

Coherent and digital image enhancement, their basic differences and constraints

Television image enhancement has long been accomplished by using analog circuits to operate on the analog television signal and thereby emphasize both horizontal and vertical transitions. Now it is feasible to perform comparable image enhancement by digital techniques operating in real time on a pulse-code-modulated NTSC television signal. Several algorithms have been developed to generate vertical and horizontal video details from PCM NTSC television signals encoded at a 10.7-MHz rate (three times the color subcarrier frequency) and at a 14.3-MHz rate (four time the subcarrier frequency). Practical design concepts are presented to implement digital image enhancers. In addition to ensuring the stability, accuracy and reliability that are the usual advantages of digital systems, digital image enhancement will enable video processing techniques to be used that can actually be performed best by digital means. In particular, more nearly optimum coring or “crispening” circuits will be possible and the detail signals will be easily programmable, which may permit automatic adaptive enhancement.

This chapter presents key dimensions of sub-Saharan African rock art (pictograms and petroglyphs). Particular attention is paid to recent approaches, the application of physico-chemical analyses, and stylistic determinations used to establish reliable chronologies. Stylistic approaches have been particularly influential in the interpretation of rock imagery, as has the identification of specific motifs (such as loincloths and aprons) that serve to indicate ritual and initiatory roles, particularly for women. The preservation of rock art and access to sites are topics of renewed concern that tend to increasingly involve local communities. In sub-Saharan Africa as in other parts of the world, rock art research is well poised to build on a long history of research, and to benefit from new techniques such as digital enhancement that are likely to considerably improve knowledge and increase the known corpus of art.

Digital Imaging: Enhancement and Authentication

Rock art studies have been strongly reliant on ethnography in recent decades. Since the 1970s, the (re)turn to ethnography has been considered short of a paradigmatic change, and it has indeed stirred a lot of theoretical discussion in the very under-theorized field of rock art research. The ethnographic turn has been mainly built around shamanism, very loosely defined here as the causal association that researchers establish between shamanic practices and rock art, and from which explanations have been sought. The application of this approach has changed through time, depending on 1) the archaeological context in which it was to be applied, 2) the use of additional sources of evidence (namely, neuropsychology), 3) the role of shamanism as a hypothesis or as an established fact. As a hypothesis it has been built on the basis of three different kinds of analogies: ethnographic, formal and uniformitarian. This paper addresses the shifting character of shamanism in South African and European Palaeolithic rock art studies, seeking to contribute at least in part to a broader reflection on the nature of analogical reasoning and its implications.

This paper describes a new approach to adaptive digital halftoning with the least squares model-based (LSMB) method. A framework is presented for the adaptive control of smoothness and sharpness of the halftone patterns according to local image characteristics. The proposed method employs explicit, quantitative models of the human visual system represented as 2D linear filters (eye filters). In contrast with the standard LSMB method where the single eye filter is employed uniformly over the image, the model parameters are controlled according to local image characteristics for each pixel. Because of the adaptive selection of eye filters for the pixels, image enhancement is incorporated into the halftoning process. Effectiveness of the proposed approach is demonstrated through experiments using real data compared with the error-diffusion algorithm and the standard LSMB method.

In recent years, with the development of digital technology, digital image processing has been widely and deeply applied in the field of computer graphics. Digital image processing system is a complex real-time system, it from the camera, fax machine and other scanning equipment to obtain image information, after digital transformation, digital image information coding, filtering, enhancement, recovery, compression, storage and other processing, finally generate visual image. This design uses TMS320C6748 as the core processor of the system, SAA7113 as the video decoding chip of the system, CPLD as the sampling controller, DDR2 chip as the external expansion memory. The ROM expansion uses NAND flash memory chip. On the basis of hardware design, combined with software algorithm to complete image processing. The system can be used in information communication, image recognition, news scene and other fields of image processing and transmission. This paper analyzes the hardware structure and data processing algorithm of the system in detail. The experimental results show that the system can not only obtain higher compression ratio, but also reduce the distortion of the reconstructed image. The image processing system has certain practicability.

Digital image noise may be introduced during acquisition, transmission, or processing and affects readability and image processing effectiveness. The accuracy of established image processing techniques, such as segmentation, recognition, and edge detection, is adversely impacted by noise. There exists an extensive body of work which focuses on circumventing such issues through digital image enhancement and noise reduction, but this work is limited by a number of constraints including the application of non-adaptive parameters, potential loss of edge detail information, and (with supervised approaches) a requirement for clean, labeled, training data. This paper, developed on the principle of Noise2Void, presents a new unsupervised learning approach incorporating a pseudo-siamese network. Our method enables image denoising without the need for clean images or paired noise images, instead requiring only noise images. Two independent branches of the network utilize different filling strategies, namely zero filling and adjacent pixel filling. Then, the network employs a loss function to improve the similarity of the results in the two branches. We also modify the Efficient Channel Attention module to extract more diverse features and improve performance on the basis of global average pooling. Experimental results show that compared with traditional methods, the pseudo-siamese network has a greater improvement on the ADNI dataset in terms of quantitative and qualitative evaluation. Our method therefore has practical utility in cases where clean images are difficult to obtain.

Digital enhancement of video images for NDT

The article presents the results of research on a newly discovered rock art site — the Bartang Cave located in the Kurtake Valley (Eastern Pamir, Republic of Tajikistan). The site was identified during the 2024 field surveys, and the archaeological study was conducted in 2025. The cave is associated with Jurassic limestone outcrops at an altitude of 4142 m above sea level. Five pigmentmade images were recorded in the cave. All of the images represent schematic icons typical of the local rock art; two of these figurines depicted anthropomorphic images. Photographic documentation followed by digital image enhancement using the DStretch method were executed; a test pit was made near the cave entrance. Archaeological materials recovered from the excavation trench mainly contained ovicaprine bone fragments. One bone sample was subjected to Accelerator Mass Spectrometry (AMS) radiocarbon dating, yielding a calibrated date of 1472–1650 CE. The authors provide correlations with other Eastern Pamir rock art sites – Shakhty, Kurteke, and Sangi-Kashida – where anthropomorphic images have been found. Comparative analysis allows us to propose a tentative chronological attribution of the Bartang Cave paintings to the Late Stone Age – Early Metal period (Mesolithic–Bronze Age). The discovery of new anthropomorphic depictions expands our understanding of the symbolic appropriation of the highmountain landscapes of the Eastern Pamirs in prehistory. The derived radiocarbon date for the first cultural layer suggests a brief episode of use of the site during the 15th–17th centuries CE.

Rock art is defined as systematic and man‐made depressions or paintings on a smooth rock surface. In contrast to other cultural monuments, they have hardly any ecological importance. Nevertheless rock art sites should be regarded as a part of the landscape, both with respect to interpretation and preservation. The method of gluing together fragmented rock art panels with an organic glue, and the repairing of cracks on rock art panels by mortar, are criticised. The author raises doubts about the ‘crumbling effect’ of mosses and the effect of ‘aggressive lichen’, postulated by other authors. The need for a long time perspective and international co‐operation in rock art preservation and conservation is underlined, and it is emphasized that experiments with new methods of conservation should be done on panels without rock art. Based on observations of an accidentally covered rock art panel in Gudbrandsdalen, Norway, a new and reversible method for stabilisation of severely weathered rock art panels is proposed, using dissolved calcium carbonate which is precipitated in a calcification process on the weathered rock and in cracks.

Rock paintings, pictographs, and petroglyphs are vulnerable to natural weathering and threatened by vandalism. Photography can provide accurate records of rock art sites for posterity, interpretation, and research. Photographic methods for red ocher rock paintings in the Canadian shield were investigated, including infrared photography, infrared luminescence, and false-color infrared; ultraviolet reflected and fluorescence photography; and cross-polarization using electronic flash. High contrast copy film with a blue filter was found to be useful. Camera stability, color temperature, film format, and exposure and color reproduction controls are discussed. Digital image processing was found to be applicable to the enhancement of photographic images of rock paintings. The photographic and photogrammetric recording of three sites from the frozen surface of the Churchill River is described. Methods for recording petroglyphs are reviewed. These have included tracing, rubbing, molding, and casting. Electronic flash raking light photography at night and stereophotogrammetry were undertaken at a petroglyph site in marble in Ontario. Machine vision systems, for example, laser scanners, could eventually find application in petroglyph recording and replication. The article includes a comprehensive bibliography of rock art recording methods.

Image contrast enhancement methods have been a topic of interest in digital image processing for various applications like satellite imaging, recognition, medical imaging, and stereo vision. This paper studies the technique for image enhancement utilizing Adaptive Histogram Equalization and Weighted Gamma Correction to cater radiometric condition and illumination variations of stereo image pairs. In the proposed method, the stereo pair images are segmented together with weighted distribution into sub-histograms supported with Histogram Equalization (HE) mapping or gamma correction and guided filtering. The experimental result shows the experimented techniques outperform compare with the original image in evaluation parameters of visual quality and image enhancement parameters via Entropy, MSE, and PSNR, etc. taken for performance analysis and validation.

Digital image enhancement techniques provide a multitude of choices for improving the visual quality of diagnostic images. Appropriate choice of such techniques is greatly influenced by the imaging modality, task at hand and viewing conditions. This sequence of two articles will provide an overview of underlying concepts, along with algorithms commonly used for radiographic image enhancement. The first article focuses on spatial domain techniques for radiographic image enhancement, with particular reference to point processing methods, histogram modification and unsharp masking.