Context-Based Defading of Archive Photographs

We present an algorithm for the enhancement of contrast in digitized archive photographic prints. It aims at producing an adaptive enhancement based on the local context of each pixel and is able to operate without direct user's intervention. A relation between the variation of contrast at different resolutions and the local Lipschitz regularity of the image is exploited. In this way, each pixel is defaded according to its nature: noise, edge, or smooth region. This strategy provides for an algorithm that drastically reduces typical, annoying artifacts like halo effects and noise amplification

Method of obtaining intensified image from developed photographic films and plates

A method is explained of obtaining intensified images from silver images on developed photographic films and plates. The steps involve converting silver of the developed film or plate to a radioactive compound by treatment with an aqueous alkaline solution of an organo-S35 compound; placing the treated film or plate in direct contact with a receiver film which is then exposed by radiation from the activated film; and developing and fixing the resulting intensified image on the receiver film

Mini Kirsch Edge Detection and Its Sharpening Effect

In computer vision, edge detection is a crucial step in identifying the objects’ boundaries in an image. The existing edge detection methods function in either spatial domain or frequency domain, fail to outline the high continuity boundaries of the objects. In this work, we modified four-directional mini Kirsch edge detection kernels which enable full directional edge detection. We also introduced the novel involvement of the proposed method in image sharpening by adding the resulting edge map onto the original input image to enhance the edge details in the image. From the edge detection performance tests, our proposed method acquired the highest true edge pixels and true non-edge pixels detection, yielding the highest accuracy among all the comparing methods. Moreover, the sharpening effect offered by our proposed framework could achieve a more favorable visual appearance with a competitive score of peak signal-to-noise ratio and structural similarity index value compared to the most widely used unsharp masking and Laplacian of Gaussian sharpening methods.  The edges of the sharpened image are further enhanced could potentially contribute to better boundary tracking and higher segmentation accuracy

A survey Of radiographic films to determine autoradiographic image intensification capabilities

A survey of radiographic films to establish the best donor/receiver combination for use in the autoradiographic image intensification technique was studied. Underexposed images of a 16 step aluminum wedge and a resolution target were made with Kodak film types XG-1, XL-5, XV-2, NMC or DuPont Cronex film. The underexposed, developed and processed films were treated in a subtractive photographic reducer (mixture of potassium ferricyanide and sodium thiosulfate) prior to radioactivation with an alkaline solution of sulfur-35 thiourea. Autoradiographs of the radioactivated films were made. Both qualitative and quantitative evaluations of the intensified images and their corresponding characteristic D-Log Rel. H curves indicate that Kodak films XG-1 and NMC formed the best donor and receiver combination. Statistical analyses of the quantitative results confirmed the choice of the XG-l/NMC combination as the best donor and receiver respectively. The use of sulfur-35 thiourea with high specific activity for activation of the underexposed image yielded disproportionate activation in the low and high density areas. Use of low specific activity sulfur-35 and potassium ferricyanide during the activation process seemed to indicate that linear activation of the underexposed step wedge can be achieved

Image Enhancement for Scanned Historical Documents in the Presence of Multiple Degradations

Historical documents are treasured sources of information but typically suffer from problems with quality and degradation. Scanned images of historical documents suffer from difficulties due to paper quality and poor image capture, producing images with low contrast, smeared ink, bleed-through and uneven illumination. This PhD thesis proposes a novel adaptative histogram matching method to remove these artefacts from scanned images of historical documents. The adaptive histogram matching is modelled to create an ideal histogram by dividing the histogram using its Otsu level and applying Gaussian distributions to each segment with iterative output refinement applied to individual images. The pre-processing techniques of contrast stretching, wiener filtering, and bilateral filtering are used before the proposed adaptive histogram matching approach to maximise the dynamic range and reduce noise. The goal is to better represent document images and improve readability and the source images for Optical Character Recognition (OCR). Unlike other enhancement methods designed for single artefacts, the proposed method enhances multiple (low-contrast, smeared-ink, bleed-through and uneven illumination). In addition to developing an algorithm for historical document enhancement, the research also contributes a new dataset of scanned historical newspapers (an annotated subset of the Europeana Newspaper - ENP – dataset) where the enhancement technique is tested, which can also be used for further research. Experimental results show that the proposed method significantly reduces background noise and improves image quality on multiple artefacts compared to other enhancement methods. Several performance criteria are utilised to evaluate the proposed method’s efficiency. These include Signal to Noise Ratio (SNR), Mean opinion score (MOS), and visual document image quality assessment (VDIQA) metric called Visual Document Image Quality Assessment Metric (VDQAM). Additional assessment criteria to measure post-processing binarization quality are also discussed with enhanced results based on the Peak signal-to-noise ratio (PSNR), negative rate metric (NRM) and F-measure.Keywords: Image Enhancement, Historical Documents, OCR, Digitisation, Adaptive histogram matchin

Work memories in super 8: the dawn of paper recycling in Brescia

This paper describes the digital acquisition and restoration of a documentary in Super 8 of the origins of citizen\u2019s awareness on paper recycling in Brescia, a city of Lombardy, northern Italy. This short movie has been shot in 1980 by ASM the public company which used to provide all the city supply (gas, water, electricity, district heating) and city transport. Now this film is part of the Fondazione ASM archive and its acquisition is part of a larger project of preservation of industrial memories in Italy. Here we describe the tools used for the acquisition and the technical choices done, together with the restoration test made. As well, we discuss the problems that one must face in trying to preserve a visual document of this kind from the unavoidable damage of time

Image Segmentation and Adaptive Contrast Enhancement for Haze Removal

Nowadays, hazing scenes are very frequent in images acquired outdoors. For such images to be used as input images of autonomous systems, it is important to restore the image details so that they can provide sufficient information to the system. As hazy images feature poor contrast due to degraded image variations, one can use a contrast enhancement method, such as CLAHE, to restore the image details. However, in case of very heavily hazy images, the image signal quality is severely degraded. Applying a strong enhancement may help to recover the details but will meanwhile generate very visible noise, affecting the image quality. In order to handle the problem of the conflict of the degree of enhancement and noise created in the process, it is thus necessary to develop a good algorithm with different enhancement based on a specific mask and signal variations in different regions. In this thesis, a novel dehazing algorithm is proposed, which aims at heavily hazy images. In order to restore effectively image details that are almost invisible in hazy images without over enhancement in other foreground areas, the proposed algorithm involves a new adaptive CLAHE process, in which a stronger enhancement is applied to the areas of weaker variations, different from an existing version of improved CLAHE with adaptive clip limit. This new CLAHE is applied only to the foreground areas, by means of a protective mask, so that there will not be noise enhancement in the atmospheric background and the other flat areas. Each input image is segmented into foreground and background areas to generate the mask. In case of heavily hazy images, the gradient amplitudes of the signals and the noise are in the same level and it is thus very difficult to distinguish foreground and background areas. A new gradient matrix has been defined and a gradient feature vector proposed to detect the locally dominant gray level variations, with a view to identifying the pixels of very weak variations in foreground areas with the noise presence. This gradient vector helps to distinguish the foreground and background areas in heavily hazy images, and the segmentation can be done effectively, which makes it possible to apply the new adaptive CLAHE without noise enhancement. The proposed algorithm has been tested with different kinds of hazy images. In case of heavily hazy image input, it performs better, in terms of image detail restoration, than existing methods based on dark-channel-prior (DCP) or other form of CLAHE. It is effective with hazy images of high dynamic range. It is also useful in case of lightly hazy images

Numerical and Field Study of Tidal and Subtidal Dynamics in a Bar-Built Estuary: Barataria Bay, Gulf of Mexico

This study investigated tidal and subtidal dynamics of water level, currents, and suspended sediment concentration (SSC) in Barataria Bay, a shallow bar-built estuary of the Northern Gulf of Mexico. First, the local and remote wind forcing contribution on subtidal water level and current variability were examined using three different methods: (i) statistical analysis of observed data, (ii) an analytical model and (iii) a 2-D barotropic numerical model. Results suggested that the remote and local wind effects were equally important at the bay mouth, however local winds were the dominant forcing driver inside the bay. The amplitudes of subtidal fluctuations induced by local winds were twice as large as the one caused by remote winds. This finding differs from those found in the existing literature, notably for Breton Sound and Lake Pontchartrain, where remote wind effect has been reported to be dominant. These differences are attributed to the different geomorphological features of the estuaries. Furthermore, the seasonality of the SSC in Barataria Pass was explored as the offshore environment transitioned from a period of high cold front activity and low river discharge to a period of low cold front activity and high river discharge. The SSC dynamics during the winter was mainly forced by resuspension in response to the cold front winds. During the spring, the average SSC (0.23 g l-1) was significantly higher than winter (0.15 g l-1) because of the strong offshore influence of the Mississippi River plume. Finally, tidal response to the relative sea level rise and marsh accretion was investigated. Contrary to previous modeling analyses in other estuaries suggesting that flooding of the low-lying land with sea level rise would increase frictional effects and thus reduce tidal range, this study suggested that tidal range in a choked tidal system like Barataria Bay increases even when accompanied by extensive land inundation. This occurs because in Barataria Bay the channel conveyance effects are larger than the frictional effects of the low-lying areas. In the lower and the middle bay, the largest increase in tidal range occurred when the marsh area was assumed to keep pace with relative sea Level rise. However, in the upper bay the largest increase in tidal range occurred when no accretion was assumed. In addition, relative sea level rise caused tidal amplification at the head of the estuary. A detailed momentum balance analysis indicated that sea level rise shifts tidal wave from a dissipative regime to a more progressive wave, which is more likely to be amplified