Exposing Photo Manipulation from Shading and Shadows

Kee, Eric; O’Brien, James F.; Farid, Hany

doi:10.1145/2629646

Cited by 69 publications

(38 citation statements)

References 38 publications

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“…An interesting challenge in this context is that of image forensics, with the goal of understanding if an image has been manipulated or not. While recently proposed methods for this purpose are based on detecting inconsistencies in the lighting from shading and shadow constraints in the image [109], future image manipulation methods will likely be able to pass these tests.…”

Section: • Future Work 115mentioning

confidence: 99%

Physically Based Rendering of Synthetic Objects in Real Environments

Kronander¹

2015

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Description of the cover imageRendering of virtual furniture illuminated with spatially varying real world illumination captured in a physical environment at IKEA Communications AB.The virtual scene was modeled by Sören and Per Larsson. Physically based rendering of synthetic objects in real environmentsCopyright © 2015 Joel Kronander (unless otherwise noted) Division of Media and Information TechnologyDepartment of Science and Technology Campus Norrköping, Printed in Sweden by LiU-Tryck, Linköping, 2015 AbstractThis thesis presents methods for photorealistic rendering of virtual objects so that they can be seamlessly composited into images of the real world. To generate predictable and consistent results, we study physically based methods, which simulate how light propagates in a mathematical model of the augmented scene. This computationally challenging problem demands both efficient and accurate simulation of the light transport in the scene, as well as detailed modeling of the geometries, illumination conditions, and material properties. In this thesis, we discuss and formulate the challenges inherent in these steps and present several methods to make the process more efficient.In particular, the material contained in this thesis addresses four closely related areas: HDR imaging, IBL, reflectance modeling, and efficient rendering. The thesis presents a new, statistically motivated algorithm for HDR reconstruction from raw camera data combining demosaicing, denoising, and HDR fusion in a single processing operation. The thesis also presents practical and robust methods for rendering with spatially and temporally varying illumination conditions captured using omnidirectional HDR video. Furthermore, two new parametric BRDF models are proposed for surfaces exhibiting wide angle gloss. Finally, the thesis also presents a physically based light transport algorithm based on Markov Chain Monte Carlo methods that allows approximations to be used in place of exact quantities, while still converging to the exact result. As illustrated in the thesis, the proposed algorithm enables efficient rendering of scenes with glossy transfer and heterogenous participating media.v Populärvetenskaplig SammanfattningEn av de största utmaningarna inom datorgrafik är att syntetisera, eller rendera, fotorealistiska bilder. Fotorealistisk rendering används idag inom många tillämpningsområden såsom specialeffekter i film, datorspel, produktvisualisering och virtuell verklighet. I många praktiska tillämpningar av fotorealistisk rendering är det viktigt att kunna placera in virtuella objekt i fotografier, så att de virtuella objekten ser verkliga ut. IKEA-katalogen, till exempel, produceras i många olika versioner för att passa olika länder och regioner. Grunden till de flesta bilderna i katalogen är oftast densamma, men symboler och standardmått på möbler varierar ofta för olika versioner av katalogen. Istället för att fotografera varje version separat kan man använda ett grundfotografi och lägga in olika virtuella objekt såsom möbler...

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Section: • Future Work 115mentioning

confidence: 99%

Physically Based Rendering of Synthetic Objects in Real Environments

Kronander¹

2015

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“…As one of the most common elements in natural scenes, the shadow also provides cues for image forensics [17,25,[28][29][30]. The method to estimate the temporal data like time of capture of an image is based on the azimuthal direction calculated from shadows in images [30].…”

Section: Related Work and Main Contributionmentioning

confidence: 99%

Image composite authentication using a single shadow observation

Cao

Zhao²,

Wang

et al. 2015

Sci. China Inf. Sci.

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The paper presents a novel method for image composite authentication based on a single shadow in an outdoor image. Existing methods based on the shadow geometry consistency involve more than two shadow observations. We relax the requirement of two shadow observations in the same scene. As a trade-off, we use the information in EXIF (Exchangeable Image File) based on which the ground truth sun elevation is calculated. We also estimate the sun elevation based on geometric constraints the scene provides, whose consistency serves as the cue to authenticate image forgery. It is the first attempt, to our best knowledge, to make use of sun elevation with shadow of one object to authenticate outdoor images. Also, the novel use of GPS (Global Positioning System), and Date and Time data of captured image makes image forensics possible even in one image containing a single shadow. Experimental results on both the synthetic data and visually plausible images demonstrate the performance of the proposed method.

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“…The shadow properties discussed so far can be utilized in image and video forensics to expose the falsification of photos and videos by detecting the shadows using their geometric and shading information [23]. Those images and videos can then be properly annotated for future forensic analysis after the removal of fake content.…”

Section: Introductionmentioning

confidence: 99%

Moving shadow detection based on stationary wavelet transform

Nagarathinam¹,

Kathavarayan²

2017

J Image Video Proc.

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Many surveillance and forensic applications face problems in identifying shadows and their removal. The moving shadow points overlap with the moving objects in a video sequence leading to misclassification of the exact object. This article presents a novel method for identifying and removing moving shadows using stationary wavelet transform (SWT) based on a threshold determined by wavelet coefficients. The multi-resolution property of the stationary wavelet transform leads to the decomposition of the frames into four different bands without the loss of spatial information. The conventional discrete wavelet transform (DWT), which has the same property, suffers from the problem of shift invariance due to the decimation operation leading to a shift in the original signal during reconstruction. Since SWT does not have the decimation operation, the problem of shift invariance is solved which makes it feasible for change detection, pattern recognition and feature extraction and retrieves the original signal without the loss of phase information also. For detection and removal of shadow, a new threshold in the form of a variant statistical parameter-"skewness"-is proposed. The value of threshold is determined through the wavelet coefficients without the requirement of any supervised learning or manual calibration. Normally, the statistical parameters like mean, variance and standard deviation does not show much variation in complex environments. Skewness shows a unique variation between the shadow and non-shadow pixels in various environments than the previously used thresholds-standard deviation and relative standard deviation. The experimental results prove that the proposed method works better than other state-of-art-methods.

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Exposing Photo Manipulation from Shading and Shadows

Cited by 69 publications

References 38 publications

Physically Based Rendering of Synthetic Objects in Real Environments

Physically Based Rendering of Synthetic Objects in Real Environments

Image composite authentication using a single shadow observation

Moving shadow detection based on stationary wavelet transform

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