论文标题
图像的Sigma Delta量化
Sigma Delta quantization for images
论文作者
论文摘要
在信号量化中,众所周知,引入对量化方案的适应性可以提高其在量化带限信号的稳定性和准确性。但是,自适应量化仅针对一维信号设计。本文的贡献是两个方面:i)。我们提出了第一个二维自适应量化方案的家族,该家族保持与一维对应物相同的数学和实际优点,而II)。我们表明,传统的一维和新的二维量化方案都可以有效地量化跳跃不连续性的信号。这些结果立即使图像对自适应量化的使用。在温和的条件下,我们表明适应性能够减少从目前最好的$ o(\ sqrt p)$从$ o(\ sqrt s)$的重建错误,其中$ s $是图像中的跳跃不连续性的数量,$ p $ p $($ p \ p \ gg s $)是样品的总数。通过应用总变化规范的解码器实现此$ \ sqrt {p/s} $ - 折叠误差的减少,其公式的启发是受压缩传感领域的数学超分辨率理论的启发。与超分辨率设置相比,我们的误差降低是可以实现的,而不需要相邻的尖峰/不连续性才能得到很好的分离,从而确保了其广泛的应用范围。 我们在数值上证明了新方案对医疗和自然图像的功效。我们观察到,对于具有小像素强度值的图像,新方法可以显着提高最新方法的图像质量。
In signal quantization, it is well-known that introducing adaptivity to quantization schemes can improve their stability and accuracy in quantizing bandlimited signals. However, adaptive quantization has only been designed for one-dimensional signals. The contribution of this paper is two-fold: i). we propose the first family of two-dimensional adaptive quantization schemes that maintain the same mathematical and practical merits as their one-dimensional counterparts, and ii). we show that both the traditional 1-dimensional and the new 2-dimensional quantization schemes can effectively quantize signals with jump discontinuities. These results immediately enable the usage of adaptive quantization on images. Under mild conditions, we show that the adaptivity is able to reduce the reconstruction error of images from the presently best $O(\sqrt P)$ to the much smaller $O(\sqrt s)$, where $s$ is the number of jump discontinuities in the image and $P$ ($P\gg s$) is the total number of samples. This $\sqrt{P/s}$-fold error reduction is achieved via applying a total variation norm regularized decoder, whose formulation is inspired by the mathematical super-resolution theory in the field of compressed sensing. Compared to the super-resolution setting, our error reduction is achieved without requiring adjacent spikes/discontinuities to be well-separated, which ensures its broad scope of application. We numerically demonstrate the efficacy of the new scheme on medical and natural images. We observe that for images with small pixel intensity values, the new method can significantly increase image quality over the state-of-the-art method.