Bayer patterned high dynamic range image reconstruction using adaptive weighting function
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Bayer patterned high dynamic range image reconstruction using adaptive weighting function Hee Kang1 , Suk Ho Lee2 , Ki Sun Song1 and Moon Gi Kang1*
Abstract It is not easy to acquire a desired high dynamic range (HDR) image directly from a camera due to the limited dynamic range of most image sensors. Therefore, generally, a post-process called HDR image reconstruction is used, which reconstructs an HDR image from a set of differently exposed images to overcome the limited dynamic range. However, conventional HDR image reconstruction methods suffer from noise factors and ghost artifacts. This is due to the fact that the input images taken with a short exposure time contain much noise in the dark regions, which contributes to increased noise in the corresponding dark regions of the reconstructed HDR image. Furthermore, since input images are acquired at different times, the images contain different motion information, which results in ghost artifacts. In this paper, we propose an HDR image reconstruction method which reduces the impact of the noise factors and prevents ghost artifacts. To reduce the influence of the noise factors, the weighting function, which determines the contribution of a certain input image to the reconstructed HDR image, is designed to adapt to the exposure time and local motions. Furthermore, the weighting function is designed to exclude ghosting regions by considering the differences of the luminance and the chrominance values between several input images. Unlike conventional methods, which generally work on a color image processed by the image processing module (IPM), the proposed method works directly on the Bayer raw image. This allows for a linear camera response function and also improves the efficiency in hardware implementation. Experimental results show that the proposed method can reconstruct high-quality Bayer patterned HDR images while being robust against ghost artifacts and noise factors. Keywords: High dynamic range; Bayer pattern; Camera response function; Ghost artifact
1 Introduction Image capturing devices like digital cameras and camcorders have recently improved remarkably. However, image sensors such as charge-coupled devices (CCD) and complementary metal-oxide semiconductors (CMOS) in these imaging devices can still only capture a limited dynamic range. As a result, when a captured scene contains a dynamic range above the given limitation, a loss of information is inevitable even if the exposure is adjusted according to the brightness of the scene. Thus, many methods based on signal processing have been proposed to reproduce scenes with a high dynamic range (HDR). *Correspondence: [email protected] 1 Department of Electric and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Korea Full list of author information is available at the end of the article
To obtain HDR images, many HDR imaging approaches utilize low dynamic range (LDR) images with different exposures [1-11]. Most of these approaches first con
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