EarthTour Presentations 2019/5/6 Adaptive data hiding based on VQ compressed image Authors: Wei-Chang Du and Wei-Jun Hsu Source: IEE Proceedings-Vision, Image and Signal Processing, Vol. 150, No. 4, August 2003, pp.233-238 Speaker: Chi-Nan Lin Date: 2004/04/21

EarthTour Presentations 2019/5/6 Outline Introduction Image coding using VQ Data hiding on VQ Experimental results Conclusions

EarthTour Presentations 2019/5/6 Introduction (1) Two fundamental requirements on data hiding in an image: The distortion of cover image should be minimized. The hiding capacity should be large enough. Usually the above two requirements are a trade off of each other. Earlier study: On spatial domain. ex. to hide data in the LSB bit.

EarthTour Presentations 2019/5/6 Introduction (2) Recent study: To hide data in compressed images. -->in palette-based images (ex.,GIF image). -->in frequency-domain images (ex.,JPEG image) -->in VQ compressed images.

Image coding using VQ(1) EarthTour Presentations 2019/5/6 Image coding using VQ(1) VQ Encoder

Image coding using VQ(2) EarthTour Presentations 2019/5/6 Image coding using VQ(2) VQ Decoder

EarthTour Presentations 2019/5/6 Data hiding on VQ (1) Pre-processing: Secret data should be compressed to save space. Secret data need to be encrypted for security (use DES, RSA etc.). Fixed embedding method: Data to hide (embed) in the LSB of indices on VQ compressed format. Codebook was divided into two sub-codebooks.

EarthTour Presentations 2019/5/6 Data hiding on VQ (2) MGLE (mean grey-level embedding) or PNNE (pairwise nearest-neighbour embedding) was used to divide the codebook (into two sub-codebooks). (MGLE) (PNNE)

EarthTour Presentations 2019/5/6 Data hiding on VQ (3) Fixed embedding method: (the secret data) codeword Yi and Yi+1 are very similar to each other. secret bit stream help decide which sub-codebook to use.

EarthTour Presentations 2019/5/6 Data hiding on VQ (4) Fixed embedding method: Two main drawbacks: Fixed capacity --> each image block can hide only one bit. Large distortion --> especially when MGLE was used. (MGLE) (PNNE)

EarthTour Presentations 2019/5/6 Data hiding on VQ (5) Adaptive embedding method: (MGLE) (PNNE) Adaptive clustering embedding (ACE)

EarthTour Presentations 2019/5/6 Data hiding on VQ (6) Adaptive embedding method: Y1 Y2 Y3 Y4 Y5 Y6 Y7 Y8 G0 Y1 Y2 G1 Y3 G2 Y4 Y5 Y6 G3 Y7 Y8 Grouping (ACE) unsigned integer value of bit stream, stop grouping

EarthTour Presentations 2019/5/6 Data hiding on VQ (7) Adaptive embedding method: G0 Y1 Y2 G1 Y3 G2 Y4 Y5 Y6 G3 Y7 Y8 Image encoded by VQ Bit stream: (1101)2=13 Y7 Y5 Y2 Y4(00) Y5(01) Y6(10) Y1(0) Y2(1) Y7(0) Y8(1) G2 : ︷ Y4 Y5 Y6 ︸ G0 : ︷ Y1 Y2 ︸ G3 : ︷ Y7 Y8 ︸ After embedding Y8 Y6 Y2 Codebook

Experimental Results (1) EarthTour Presentations 2019/5/6 Experimental Results (1) Original image VQ PSNR:31.24 MGLE PNNE ACE Results for various embedding methods (capacity = 16 Kbit)

Experimental Results (2) EarthTour Presentations 2019/5/6 Experimental Results (2)

Conclusions Based on VQ compressed images. ACE (Adaptive Clustering Embedding) has higher hiding capacity and better image quality than traditional methods. It is possible for ACE to be applied to other media in which VQ is applicable.