Contrast Enhancement of Brightness-Distorted Images by Improved Adaptive Gamma Correction

As an efficient image contrast enhancement (CE) tool, adaptive gamma correction (AGC) was previously proposed by relating gamma parameter with cumulative distribution function (CDF) of the pixel gray levels within an image. ACG deals well with most dimmed images, but fails for globally bright images and the dimmed images with local bright regions. Such two categories of brightness-distorted images are universal in real scenarios, such as improper exposure and white object regions. In order to attenuate such deficiencies, here we propose an improved AGC algorithm. The novel strategy of negative images is used to realize CE of the bright images, and the gamma correction modulated by truncated CDF is employed to enhance the dimmed ones. As such, local over-enhancement and structure distortion can be alleviated. Both qualitative and quantitative experimental results show that our proposed method yields consistently good CE results

An Interactive Color Picker that Ensures WCAG2.0 Compliant Color Contrast Levels

AbstractInsufficient contrast between text and the background is a common problem on the web. WCAG2.0 addresses this problem, but the definition is hard to understand for most designers. Therefore, some web designers check their designs with contrast checking tools after the design is finished. If the design does not meet the WCAG2.0 guidelines the designer will have to go back and make adjustments. To overcome this problem a color picker tool is proposed that allows designers to select WCAG2.0 compliant colors during the design process thus eliminating the need for post-design color adjustments. First, the designer selects the first color freely from all available colors. Subsequently, only colors are presented that meets the chosen contrast level. In addition to being a design tool, it also serves as a pedagogical visualization aid that can help students and designers better understand the complex relationships between colors palettes and their contrasts

OBJECT-BASED IMAGE ENHANCEMENT TECHNIQUE FOR GRAY SCALE IMAGES

ABSTRACT Image enhancement technique plays vital role in improving the quality of the image. Enhancement technique basically enhances the foreground information and retains the background and improve the overall contrast of an image. In some case the background of an image hides the structural information of an image. This paper proposes an algorithm which enhances the foreground image and the background part separately and stretch the contrast of an image at inter-object level and intra-object level and then combines it to an enhanced image. The results are compared with various classical methods using image quality measures. KEYWORDS Image Enhancement, Morphological watershed segmentation, Object-based contrast enhancement, Interobject stretching, Intra-object stretching

MORPHOLOGICAL BACKGROUND DETECTION & ENHANCEMENT OF IMAGES

The paper deals with detection and the enhancement of images which contains poor lighting. Using the Mathematical Morphological Transformations. If an image captured the background is not clear of that image, by using the morphological operations we can detect the background of the image and enhance the image. Weber’s law is used to analyse the blocks and utilizing the opening by reconstruction to define the Multibackground notion. Some Morphological operations such as (Erosion, Dilation, Compound operation such as Opening by reconstruction, Erosion-Dilation method) and Block Analysis is used to detect the background of images. Analysis of above mention methods illustrated through the processing of images with different dark background images

Automated Localization of Blood Vessels in Retinal Images

Vessel structure is one of the most important parts of the retina which physicians can detect many diseases by analysing its features. Localization of blood vessels in retina images is an important process in medical image analysis. This process is also more challenging with the presence of bright and dark lesions. In this thesis, two automated vessel localization methods to handle both healthy and unhealthy (pathological) retina images are analyzed. Each method consists of two major steps and the second step is the same in the two methods. In the first step, an algorithm is used to decrease the effect of bright lesions. In Method 1, this algorithm is based on K- Means segmentation, and in Method 2, it is based on a regularization procedure. In the second step of both methods, a multi-scale line operator is used to localize the line-shaped vascular structures and ignore the dark lesions which are generally assumed to have irregular patterns. After the introduction of the methods, a detailed quantitative and qualitative comparison of the methods with one another as well as the state-of-the-art solutions in the literature based on the segmentation results on the images of the two publicly available datasets, DRIVE and STARE, is reported. The results demonstrate that the methods are highly comparable with other solutions

Contrôle automatique des conditions d'affichage d'une image par un projecteur

L'utilisation d'un projecteur dans différentes applications et environnements soulève la nécessité d'adapter et de contrôler l'image affichée en fonction des conditions d'affichage. L'image affichée par exemple dans un environnement éclairé peut apparaître avec des couleurs saturées et un contraste atténué. De même, son apparence peut être affectée par la réflectance et la géométrie de l'écran sur lequel l'image est projetée. Dans ce mémoire, nous proposons une approche pour contrôler l'apparence de l'image affichée par la modélisation des différents facteurs affectants son affichage. Cette approche est basée sur le modèle de formation de l'image perçue et la constance de couleur entre les images observées. L'approche proposée unifie la compensation des effets de la lumière ambiante et de la réflectance de l'écran. Nous argumentons que le modèle proposé est plus général que certains modèles de compensation utilisés pour la constance de couleurs. L'approche proposée estime l'illuminant de l'environnement d'affichage et l'illuminant cible, la réflectance de l'écran utilisé ainsi que la réflectance de l'écran cible. Une opération complémentaire pour la compensation de contraste est dérivée de la loi de Weber. Cette compensation permet d'adapter le contraste de l'image affichée conformément à l'intensité de la lumière ambiante. L'approche proposée est vérifiée expérimentalement dans des environnements éclairés et en utilisant des écrans non blancs. Elle permet de camoufler l'effet de l'écran utilisé dans l'affichage et de simuler les effets d'autres écrans cibles. Notre approche peut être utile dans certains domaines tels que le camouflage et la simulation pour des applications d'art visuel et performatif