Revisiting Pentland’s estimator of light source direction

Chojnacki, Wojciech; Brooks, Michael J.; Gibbins, Danny

doi:10.1364/josaa.11.000118

Cited by 34 publications

(18 citation statements)

References 5 publications

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“…Also assume for simplicity that x is given (in some works, x as well is considered as unknown, see e.g. [20,21], even if this new problem is sometimes ill-posed [22]). Recalling that, for a Lambertian surface of uniform albedo equal to 1, R(n(x)) = n(x), Eq.1 can be written, using Eq.2:…”

Section: Problem Formulationmentioning

confidence: 99%

A Robust Method for Shape from Shading Using Genetic Algorithm Based on Matrix Code

Mansour

2012

AJCAM

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In this paper, a method for reconstructing a 3-D shape of an object from a 2-D shading image using a Genetic Algorithm (GA), which is an optimizing technique based on mechanisms of natural selection. The 3D-shape is recovered through the analysis of the gray levels in a single image of the scene. This problem is ill-posed except if some additional assumptions are made. In the proposed method, shape from shading is addressed as an energy minimization problem. The traditional deterministic approach provides efficient algorithms to solve this problem in terms of time but reaches its limits since the energy associated with shape from shading can contain multiple deep local minima. Genetic Algorithm is used as an alternative approach which is efficient at exploring the entire search space. The Algorithm is tested in both synthetic and real image and is found to perform accurate and efficient results.

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Section: Problem Formulationmentioning

confidence: 99%

A Robust Method for Shape from Shading Using Genetic Algorithm Based on Matrix Code

Mansour

2012

AJCAM

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“…Under the assumption that surface of objects in the image is Lambertian, the intensity I at a point of the image can be calculated [26,27] by the following equation…”

Section: New Proposalmentioning

confidence: 99%

A novel method for detecting light source for digital images forensic

Roy

Mitra

Agrawal

2011

Opto-Electronics Review

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Manipulation in image has been in practice since centuries. These manipulated images are intended to alter facts — facts of ethics, morality, politics, sex, celebrity or chaos. Image forensic science is used to detect these manipulations in a digital image. There are several standard ways to analyze an image for manipulation. Each one has some limitation. Also very rarely any method tried to capitalize on the way image was taken by the camera. We propose a new method that is based on light and its shade as light and shade are the fundamental input resources that may carry all the information of the image. The proposed method measures the direction of light source and uses the light based technique for identification of any intentional partial manipulation in the said digital image. The method is tested for known manipulated images to correctly identify the light sources. The light source of an image is measured in terms of angle. The experimental results show the robustness of the methodology.

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“…The estimation of the illumination conditions in still images and videos is therefore an important issue for many image analysis applications. This mainly consists of the following (1) the definition of an illumination model [30,38]; (2) the detection of self-and cast shadow areas [17,38]; and (3) the estimation of the light source characteristics (direction and position) [4,29].…”

Section: Introductionmentioning

confidence: 99%