无需训练的图像去噪新方法,速度远超深度学习模型且适配多种图像格式。
GALOSH: Blind, Training-Free Denoising of Raw Bayer and sRGB Images by Parallel-Friendly Local Shrinkage

- 摒弃传统搜索机制,采用局部固定计算流程实现高效去噪。
- 在四个真实噪声数据集上超越经典算法,接近有监督模型性能。
- 适合追求低延迟、跨域兼容的嵌入式或实时处理场景使用。
传统无训练去噪方法如BM3D和非局部均值依赖内容相关的块匹配,其内存访问和数据依赖控制流难以并行,无法实现固定延迟。学习型去噪器虽效果最佳,但需训练数据,在域外性能下降,且每像素计算量大,通常依赖GPU。本文提出GALOSH(广义Anscombe局部收缩),重新设计无训练去噪:完全去除搜索,兼顾多领域覆盖、速度与质量——包含盲态泊松-高斯噪声拟合、广义Anscombe变换、两阶段局部Walsh-Hadamard收缩(亮度)、亮度引导的局部回归(色度);两种不同算子分别针对感知差异明显的噪声分量,各自具备强度调控能力。所有阶段均为局部、数据无关、结构规则,每个像素执行相同计算图。单一核心支持原始Bayer马赛克与sRGB/YUV图像。在四个真实噪声基准(SIDD Medium和RawNIND,含原始与sRGB)上,GALOSH始终优于对比的盲态无训练方法,甚至在已知噪声水平下仍超越BM3D与NLM家族;在原始数据上接近训练网络表现,但在高ISO sRGB上仍低于域内训练模型。无搜索设计使其极快:在同一GPU上比深度学习基线快7至650倍,且是唯一可在普通CPU上实用的强方法。其固定、数据无关结构天然适配定点与流式硬件,经操作计数分析及成功实现的INT16定点版本验证。
原文摘要 · Abstract (English)
Classical training-free denoisers such as BM3D and non-local means owe much of their strength to search: content-dependent block matching whose memory traffic and data-dependent control flow parallelize poorly and preclude fixed-latency implementations. Learned denoisers reach the highest quality, but they need training data, degrade outside their training domain (which we also observe), and carry per-pixel compute budgets that effectively require a GPU. We present GALOSH (Generalized Anscombe LOcal SHrinkage), a redesign of training-free denoising that removes the search entirely and aims at multi-domain coverage, speed, and quality at once: a blind per-image Poisson-Gaussian noise fit, a generalized Anscombe transform, a two-pass local Walsh-Hadamard shrinkage of luminance, and a luminance-guided local regression of chrominance -- two deliberately different operators for the two perceptually different noise components, each with its own strength control. Every stage is local, data-independent, and regular -- the same computation graph for every pixel of every image. One core serves two domains: raw Bayer mosaics and sRGB/YUV images. On four real-noise benchmarks (SIDD Medium and RawNIND, raw and sRGB) GALOSH is consistently the strongest among the tested blind, training-free methods -- surpassing BM3D- and NLM-family baselines even when those are given an oracle noise level -- and approaches trained networks on raw data while remaining below in-domain trained networks at high ISO in sRGB. Being search-free makes it fast: 7x-650x faster than the DL baselines on the same GPU at full benchmark size, and the only strong method in the comparison that also runs practically on plain CPUs. The fixed, data-independent structure is designed to map naturally onto fixed-point and streaming hardware, supported by an operation-count analysis and a working INT16 fixed-point realization.
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