提出新型图像特征提取方法,提升分类对形变和噪声的鲁棒性。
Normalized Radon Cumulative Distribution Transforms for Invariance and Robustness in Optimal Transport Based Image Classification
- 基于归一化R-CDT变换,增强对仿射与非仿射变形的不变性。
- 在小样本下保持类别线性可分,对局部形变和脉冲噪声有强鲁棒性。
- 适合水印识别等实际图像分类任务,尤其面对测量过程扰动场景。
Radon累积分布变换(R-CDT)是一种易于计算的特征提取器,特别适用于小样本图像分类任务。它与切片Wasserstein距离密切相关,并可保证由平移或缩放引起的图像类别具有线性可分性。然而在真实应用中,如细纹学中的水印识别,数据常受测量过程引起的广义仿射变换影响。为此,我们此前提出最大归一化R-CDT,仅通过基本运算即可保证任意仿射变换下的可分性。本文继续研究该方法在非仿射图像形变下的鲁棒性。敏感性分析表明,只要样本间的Wasserstein-infinity距离可控,其可分性即保持稳定;而该距离仅允许微小局部形变。因此,我们进一步引入均值归一化的R-CDT版本,其鲁棒性关联于Wasserstein-2距离,可覆盖由脉冲噪声引起的形变。理论结果经数值实验验证,新特征提取器在抵抗局部非仿射形变和脉冲噪声方面表现有效。
原文摘要 · Abstract (English)
The Radon cumulative distribution transform (R-CDT), is an easy-to-compute feature extractor that facilitates image classification tasks especially in the small data regime. It is closely related to the sliced Wasserstein distance and provably guaranties the linear separability of image classes that emerge from translations or scalings. In many real-world applications, like the recognition of watermarks in filigranology, however, the data is subject to general affine transformations originating from the measurement process. To overcome this issue, we recently introduced the so-called max-normalized R-CDT that only requires elementary operations and guaranties the separability under arbitrary affine transformations. The aim of this paper is to continue our study of the max-normalized R-CDT especially with respect to its robustness against non-affine image deformations. Our sensitivity analysis shows that its separability properties are stable provided the Wasserstein-infinity distance between the samples can be controlled. Since the Wasserstein-infinity distance only allows small local image deformations, we moreover introduce a mean-normalized version of the R-CDT. In this case, robustness relates to the Wasserstein-2 distance and also covers image deformations caused by impulsive noise for instance. Our theoretical results are supported by numerical experiments showing the effectiveness of our novel feature extractors as well as their robustness against local non-affine deformations and impulsive noise.
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