论文标题

归一流流量的有损图像压缩

Lossy Image Compression with Normalizing Flows

论文作者

Helminger, Leonhard, Djelouah, Abdelaziz, Gross, Markus, Schroers, Christopher

论文摘要

基于深度学习的图像压缩最近见证了令人兴奋的进步,在某些情况下,甚至设法超越了数十年来已经建立和完善的基于转换编码的方法。但是,深层图像压缩的最新解决方案通常采用自动编码器,这些自动编码器将输入映射到较低的尺寸潜在空间,因此在量化之前已经不可逆地丢弃信息。因此,它们固有地限制了可以涵盖的质量水平的范围。相比之下,图像压缩中的传统方法可以提高质量较大的水平。有趣的是,他们在执行明确放弃信息的量化步骤之前采用可逆转换。受此启发,我们提出了一种深层图像压缩方法,该方法可以通过利用归一化的流量来学习从图像空间到潜在表示的界限,从而能够从低比特率到几乎无损质量。除此之外,我们还展示了解决方案所特有的进一步优势,例如即使多次执行,也可以通过重新编码来维持恒定质量结果的能力。据我们所知,这是探索利用归一流流量以进行有损图像压缩的机会的第一项工作。

Deep learning based image compression has recently witnessed exciting progress and in some cases even managed to surpass transform coding based approaches that have been established and refined over many decades. However, state-of-the-art solutions for deep image compression typically employ autoencoders which map the input to a lower dimensional latent space and thus irreversibly discard information already before quantization. Due to that, they inherently limit the range of quality levels that can be covered. In contrast, traditional approaches in image compression allow for a larger range of quality levels. Interestingly, they employ an invertible transformation before performing the quantization step which explicitly discards information. Inspired by this, we propose a deep image compression method that is able to go from low bit-rates to near lossless quality by leveraging normalizing flows to learn a bijective mapping from the image space to a latent representation. In addition to this, we demonstrate further advantages unique to our solution, such as the ability to maintain constant quality results through re-encoding, even when performed multiple times. To the best of our knowledge, this is the first work to explore the opportunities for leveraging normalizing flows for lossy image compression.

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