Estimation of the Embedding Capacity in Pixel-pair based Watermarking Schemes

TL;DR

This paper introduces an efficient method to estimate the maximum embedding capacity of images for reversible watermarking schemes, enabling capacity analysis without actual watermark embedding, thus saving computational resources.

Contribution

The paper presents a novel, efficient algorithm for estimating multi-pass embedding capacity in pixel-pair based watermarking schemes without embedding watermarks.

Findings

The proposed method accurately estimates multi-pass embedding capacity.

The algorithm is significantly more efficient than actual watermark embedding.

It provides bounds on the embedding capacity.

Abstract

Estimation of the Embedding capacity is an important problem specifically in reversible multi-pass watermarking and is required for analysis before any image can be watermarked. In this paper, we propose an efficient method for estimating the embedding capacity of a given cover image under multi-pass embedding, without actually embedding the watermark. We demonstrate this for a class of reversible watermarking schemes which operate on a disjoint group of pixels, specifically for pixel pairs. The proposed algorithm iteratively updates the co-occurrence matrix at every stage, to estimate the multi-pass embedding capacity, and is much more efficient vis-a-vis actual watermarking. We also suggest an extremely efficient, pre-computable tree based implementation which is conceptually similar to the co-occurrence based method, but provides the estimates in a single iteration, requiring a complexity akin to that of single pass capacity estimation. We also provide bounds on the embedding capacity. We finally show how our method can be easily used on a number of watermarking algorithms and specifically evaluate the performance of our algorithms on the benchmark watermarking schemes of Tian [11] and Coltuc [6].