A Review of an Old Dilemma: Demosaicking First, or Denoising First?
This addresses a key dilemma in digital camera pipelines for imaging applications, but it is incremental as it reviews and evaluates existing strategies rather than introducing a new method.
The paper tackles the problem of whether to apply denoising or demosaicking first in reconstructing full-color images from noisy color filter arrays, concluding that demosaicking first followed by adapted denoising yields the best results.
Image denoising and demosaicking are the most important early stages in digital camera pipelines. They constitute a severely ill-posed problem that aims at reconstructing a full color image from a noisy color filter array (CFA) image. In most of the literature, denoising and demosaicking are treated as two independent problems, without considering their interaction, or asking which should be applied first. Several recent works have started addressing them jointly in works that involve heavy weight CNNs, thus incompatible with low power portable imaging devices. Hence, the question of how to combine denoising and demosaicking to reconstruct full color images remains very relevant: Is denoising to be applied first, or should that be demosaicking first? In this paper, we review the main variants of these strategies and carry-out an extensive evaluation to find the best way to reconstruct full color images from a noisy mosaic. We conclude that demosaicking should applied first, followed by denoising. Yet we prove that this requires an adaptation of classic denoising algorithms to demosaicked noise, which we justify and specify.