Lossless Data Embedding in BTC Codes Based on Prediction and Histogram Shifting

Abstract

This paper proposes a lossless data embedding method for Block Truncation Coding (BTC) compressed images based on prediction and histogram shifting techniques. Because BTC is easy to implement, and requires significantly less CPU cost, it has arouse widely attention in applications where real-time processing is demanded. For the existing lossless data embedding method in BTC codes, the decoder has to be specifically designed so that the spatial domain image can perfectly reconstructed from the compressed codes. Therefore, the application of these methods is limited. In the proposed embedding method, we slightly modified the quantization values of BCT codes to embed data losslessly, and a standard BTC decoder can be used to decode the BTC codes. The embedded secret messages can be extracted at the receiver side with the correct key. The experimental results revealed that the proposed method not only recovers the stego image to its original one, but also preserved a high image quality.

Reversible Data Hiding in Block Truncation Coding Compressed Images Using Quantization Level Swapping and Shifting

“…As a result, the traditional RDH methods cannot directly be applied to images in compressed format. Some RDH methods have been proposed so far for various compressed domain, such as vector quantization (VQ) [19], JPEG [20], and block truncation coding (BTC) compressed images [21]- [25], to accommodate different requirements for various applications. Since BTC [26] simply represents an image block by two quantization levels (QLs) and a bitmap, it requires insignificant computational cost but also offers acceptable image quality and compression rate.…”

“…Till now, only a few RDH methods for BTC compressed images (or BTC codes) are proposed. Hong et al [21] proposed a RDH in BTC codes based on prediction and histogram shifting. This method partitioned higher and lower QLs into blocks, and then a reversible method is applied to these blocks for data embedment.…”

“…Chang et al [23] also proposed a reversible method for BTC codes using side match. Although this method achieves higher payload than that of [21] and [22], it cannot be decoded by a standard BTC decoder and thus the application is limited. Lo et al [24] made use of histogram shifting technique to embed secret data into the QLs and the embedded codes still follows the standard BTC format.…”