Single Shot High Dynamic Range Imaging Using Piecewise Linear Estimators

Cecilia Aguerrebere           Andrés Almansa           Yann Gousseau           Julie Delon           Pablo Musé          

Télécom ParisTech          Université Paris Descartes          IIE, U. de República

Result using real data. Left: Tone mapped HDR image obtained by the proposed approach (11.4 stops). Middle top: Raw image with spatially varying exposure levels. Middle bottom: Mask of unknown (black) and known (white) pixels. In the regions with unknown pixels, the percentage of missing pixels varies between 25% to 40%. Right: Extracts of the scene.

Result using real data. Left: Tone mapped HDR image obtained by the proposed approach (15.6 stops). Right top: Extracts of the scene. Right bottom: Mask of unknown (black) and known (white) pixels. In the brightest part of the building 73% of the pixels are unknown. Despite this fact, the reconstructed HDR image does not exhibit any visible artifact.

Abstract

Building high dynamic range (HDR) images by combining photographs captured with different exposure times present several drawbacks, such as the need for global alignment and motion estimation in order to avoid ghosting artifacts. The concept of spatially varying pixel exposures (SVE) proposed by Nayar et al. enables to capture in only one shot a very large range of exposures while avoiding these limitations. In this paper, we propose a novel approach to generate HDR images from a single shot acquired with spatially varying pixel exposures. The proposed method makes use of the assumption stating that the distribution of patches in an image is well represented by a Gaussian Mixture Model. Drawing on a precise modeling of the camera acquisition noise, we extend the piecewise linear estimation strategy developed by Yu et al. for image restoration. The proposed method permits to reconstruct an irradiance image by simultaneously estimating saturated and under-exposed pixels and denoising existing ones, showing significant improvements over existing approaches.

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For any question or comment don't hesitate to contact me at aguerreb [at] telecom-paristech.fr