Method to increase the contrast and reduce the noise of underwater image.Applied histogram modification of integrated RGB and HSV color models.Mapping the image histogram according to Rayleigh distribution.Limiting the dynamic range of color models to reduce under- and over-enhanced areas.Outperforms other state-of-the-art methods in term of contrast and noise reduction. The physical properties of water cause light-induced degradation of underwater images. Light rapidly loses intensity as it travels in water, depending on the color spectrum wavelength. Visible light is absorbed at the longest wavelength first. Red and blue are the most and least absorbed, respectively. Underwater images with low contrast are captured due to the degradation effects of light spectrum. Therefore, the valuable information from these images cannot be fully extracted for further processing. The current study proposes a new method to improve the contrast and reduce the noise of underwater images. The proposed method integrates the modification of image histogram into two main color models, Red-Green-Blue (RGB) and Hue-Saturation-Value (HSV). In the RGB color model, the histogram of the dominant color channel (i.e., blue channel) is stretched toward the lower level, with a maximum limit of 95%, whereas the inferior color channel (i.e., red channel) is stretched toward the upper level, with a minimum limit of 5%. The color channel between the dominant and inferior color channels (i.e., green channel) is stretched to both directions within the whole dynamic range. All stretching processes in the RGB color model are shaped to follow the Rayleigh distribution. The image is converted into the HSV color model, wherein the S and V components are modified within the limit of 1% from the minimum and maximum values. Qualitative analysis reveals that the proposed method significantly enhances the image contrast, reduces the blue-green effect, and minimizes under- and over-enhanced areas in the output image. For quantitative analysis, the test with 300 underwater images shows that the proposed method produces average mean square error (MSE) and peak signal to noise ratio (PSNR) of 76.76 and 31.13, respectively, which outperform six state-of-the-art methods.

Underwater image quality enhancement through integrated color model with Rayleigh distribution

A method of integration global and local contrast stretching is proposed to increase underwater image quality.The integrated modification of RGB and HSV color model is applied in the proposed method.Resultant image outperforms the current state-of-the-arts techniques in terms of image details and noise.300 low contrast underwater images are used in the experiment. The attenuation of the light that travels through a water medium subjects underwater images to several problems. As a result of low contrast and color performance, images are unclear and lose important information. Therefore, the objects in these images can hardly be differentiated from the background. This study proposes a new method called dual-image Rayleigh-stretched contrast-limited adaptive histogram specification, which integrates global and local contrast correction. The aims of the proposed method are to increase image details and to improve the visibility of underwater images while enhancing image contrasts. The two main steps of the proposed method are contrast and color corrections; an underwater image undergoes the former before the latter. Global contrast correction generates dual-intensity images, which are then integrated to produce contrast-enhanced resultant images. Subsequently, such images are processed locally to enhance details. The color of the images is also corrected to improve saturation and brightness. Qualitative and quantitative results show that the contrast of the resultant image improves significantly. Moreover, image detail and color are adequately enhanced; thus, the proposed approach outperforms current state-of-the-art methods.

Enhancement of low quality underwater image through integrated global and local contrast correction

This paper presents a study to analyze the use of augmented reality (AR) for delivering multimedia content to support the teaching and learning process of the digestive and circulatory systems at the primary school level, and its impact on knowledge retention. Our AR application combines oral explanations and 3D models and animations of anatomical structures. A validation study was conducted with fourth grade students in order to evaluate the effect of our tool on knowledge retention. In this study, we attempt to verify whether students using the AR application retained more concepts that those learning the topic in a traditional setting. Results show an increased knowledge retention on students using AR multimedia contents as opposed to those following a traditional course, which validates AR technology as a promising tool to improve students’ motivation and interest, and to support the learning and teaching process in educational contexts.

/pdf/delivering-educational-multimedia-contents-through-an-6omrc8u2cf.pdf

Delivering educational multimedia contents through an augmented reality application: a case study on its impact on knowledge acquisition and retention

. Recovering correct or at least realistic colors of underwater scenes is a very challenging issue for imaging techniques, since illumination conditions in a refractive and turbid medium as the sea are seriously altered. The need to correct colors of underwater images or videos is an important task required in all image-based applications like 3D imaging, navigation, documentation, etc. Many imaging enhancement methods have been proposed in literature for these purposes. The advantage of these methods is that they do not require the knowledge of the medium physical parameters while some image adjustments can be performed manually (as histogram stretching) or automatically by algorithms based on some criteria as suggested from computational color constancy methods. One of the most popular criterion is based on gray-world hypothesis, which assumes that the average of the captured image should be gray. An interesting application of this assumption is performed in the Ruderman opponent color space lαβ, used in a previous work for hue correction of images captured under colored light sources, which allows to separate the luminance component of the scene from its chromatic components. In this work, we present the first proposal for color correction of underwater images by using lαβ color space. In particular, the chromatic components are changed moving their distributions around the white point (white balancing) and histogram cutoff and stretching of the luminance component is performed to improve image contrast. The experimental results demonstrate the effectiveness of this method under gray-world assumption and supposing uniform illumination of the scene. Moreover, due to its low computational cost it is suitable for real-time implementation.

/pdf/a-new-color-correction-method-for-underwater-imaging-3zhxd4yk3h.pdf

a New Color Correction Method for Underwater Imaging

Automatic system for improving underwater image contrast and color through recursive adaptive histogram modification

Underwater imaging is quite a challenging in the area of photography especially for low resolution and ordinary digital camera. There are a few problems occur in underwater images such as limited range visibility, low contrast, non uniform lighting, blurring, bright artefacts, color diminished and noise. This paper concentrates on color diminished. Significant application of standard computer vision techniques to underwater imaging is required in dealing with the said problems. Both manual and auto level techniques are used to record the mean values of the stretched histogram. The objective of the paper is to identify which technique is more significant in terms of color correction. It is hoped that the finding will benefit to non divers to visualize the underwater as the real underwater world.

Significance level of image enhancement techniques for underwater images

The visual of an underwater images sometimes does not representing the real world objects. Light absorption and diffusion somehow degrade the clarity of the images. In order to improve visualization of underwater images, an approach using color correction based on histogram is used. The reason why this approach is used is simply because it improves contrast by redistributing intensity distributions and computes a uniform histogram. Histogram in Photoshop is a graph that shows the digital image balance and also placement of the pixels in an image. A few examples are shown in this paper.

Image enhancement of underwater habitat using color correction based on histogram

Augmented Reality (AR) is a term for a view of a physical real world environment whose elements are combined with virtual computer based imaginary that will create a mixed reality. This paper overviews on the process of the development of an AR application of Malaysia's Underwater Habitat. Due to time, cost and manpower constraints, the development of the application will be based on Redang Island in Terengganu. It is one of the most popular islands in Malaysia among scuba divers. To create this AR application, ARToolKit can be taken into consideration. It is hope that the application could help first time scuba divers to explore and experience before they go into the real underwater. This application also will provide information about the chosen underwater habitat. Therefore this paper is intended to give an overview of augmented reality application of Malaysia's underwater habitat. It can also help to promote tourism in Malaysia. This application will benefit the Department of Fisheries Malaysia through warehousing the information such as images, audios and videos of underwater habitat. Another stakeholder that has the advantage is Malaysian Ministry of Culture, Arts and Tourism. It is because of the application will promote Malaysia. The application also will contribute to Professional Association Diving's Instructor (PADI) as it can be one of the supporting tool in their teaching aids for scuba divers.

Mohd Kushairi B. Mohd Rajuddin

Papers

Significance level of image enhancement techniques for underwater images

Image enhancement of underwater habitat using color correction based on histogram

An overview of augmented reality of underwater habitat