Improved Real-time Image Smoothing with Weak Structures Preserved and High-contrast Details Removed

TL;DR

This paper introduces an improved real-time image smoothing method that better preserves weak structures and removes high-contrast details by using alternative pixel values in the optimization process, enhancing quality and efficiency.

Contribution

It extends the iterative least squares method by replacing gradient-based penalties with adjustable pixel values, enabling better structure preservation and detail removal in real-time.

Findings

Outperforms existing methods in preserving weak structures.

Achieves higher efficiency with fewer iterations.

Provides superior quality in detail removal and structure preservation.

Abstract

Image smoothing is by reducing pixel-wise gradients to smooth out details. As existing methods always rely on gradients to determine smoothing manners, it is difficult to distinguish structures and details to handle distinctively due to the overlapped ranges of gradients for structures and details. Thus, it is still challenging to achieve high-quality results, especially on preserving weak structures and removing high-contrast details. In this paper, we address this challenge by improving the real-time optimization-based method via iterative least squares (called ILS). We observe that 1) ILS uses gradients as the independent variable in its penalty function for determining smoothing manners, and 2) the framework of ILS can still work for image smoothing when we use some values instead of gradients in the penalty function. Thus, corresponding to the properties of pixels on structures or not, we compute some values to use in the penalty function to determine smoothing manners, and so we can handle structures and details distinctively, no matter whether their gradients are high or low. As a result, we can conveniently remove high-contrast details while preserving weak structures. Moreover, such values can be adjusted to accelerate optimization computation, so that we can use fewer iterations than the original ILS method for efficiency. This also reduces the changes onto structures to help structure preservation. Experimental results show our advantages over existing methods on efficiency and quality.