No abstract

Sparse representation has proven to be a promising approach to image super-resolution, where the low resolution (LR) image is usually modeled as the down-sampled version of its high resolution (HR) counterpart after blurring. When the blurring kernel is the Dirac delta function, i.e., the LR image is directly down-sampled from its HR counterpart without blurring, the super-resolution problem becomes an image interpolation problem. In such case, however, the conventional sparse representation models (SRM) become less effective because the data fidelity term will fail to constrain the image local structures. In natural images, fortunately, the many nonlocal similar patches to a given patch could provide nonlocal constraint to the local structure. In this paper we incorporate the image nonlocal self-similarity into SRM for image interpolation.More specifically, a nonlocal autoregressive model (NARM) is proposed and taken as the data fidelity term in SRM. We show that the NARM induced sampling matrix is less coherent with the representation dictionary, and consequently makes SRM more effective for image interpolation. Our extensive experimental results demonstrated that the proposed NARM based image interpolation method can effectively reconstruct the edge structures and suppress the jaggy/ringing artifacts, achieving the best image interpolation results so far in term of PSNR as well as perceptual quality metrics such as SSIM and FSIM.

-This paper describes the design of color filterarrays (CFAs)

No abstract

No abstract

Abstract-Single-sensor digital color cameras use a process called color demosaicking to produce full color images from the data captured by a color filter array (CFA). The quality of demosaicked images is degraded due to the sensor noise introduced during the image acquisition process. The conventional solution to combating CFA sensor noise is demosaicking first, followed by a separate denoising processing. This strategy will generate many noise-caused color artifacts in the demosaicking process, which are hard to remove in the denoising process. Few denoising schemes that work directly on the CFA images have been presented because of the difficulties arisen from the red, green and blue interlaced mosaic pattern, yet a well designed "denoising first and demosaicking later" scheme can have advantages such as less noise-caused color artifacts and cost-effective implementation. This paper presents a principle component analysis (PCA) based spatially-adaptive denoising algorithm, which works directly on the CFA data using a supporting window to analyze the local image statistics. By exploiting the spatial and spectral correlations existed in the CFA image, the proposed method can effectively suppress noise while preserving color edges and details. Experiments using both simulated and real CFA images indicate that the proposed scheme outperforms many existing approaches, including those sophisticated demosaicking and denoising schemes, in terms of both objective measurement and visual evaluation.Index Terms-Adaptive denoising, Bayer pattern, color filter array (CFA), demosaicking, principle component analysis (PCA).

Abstract-A postprocessing method for the correction of visual demosaicking artifacts is introduced. The restored, full-color images previously obtained by cost-effective color filter array interpolators are processed to improve their visual quality. Based on a localized color ratio model and the original underlying Bayer pattern structure, the proposed solution impressively removes false colors while maintaining image sharpness. At the same time, it yields excellent improvements in terms of objective image quality measures.Index Terms-Bayer pattern, color artifact removing, color filter array (CFA) interpolation, demosaicked image postprocessing, human visual system, subjective evaluation.

No abstract