# A Large Capacity Histogram-Based Watermarking Algorithm for Three Consecutive Bins
## 4 Experimental Results and Analysis
### Embedding Capacity and Perceptual Similarity
#### 4.1.2 Comparison with the State-of-the-Art Methods  
In this section, we further evaluate the effectiveness of the proposed method by comparing it with those suggested in [13; 17; 18]. All of the parameter settings for different algorithms are shown in Table 3. The corresponding PSNRs are compared in Table 4. It can be observed that our method provided a preferable visual quality of the watermarked image; meanwhile, it ensured more information could be embedded into the pixels located at the same bins. Our algorithm, with respect to the existing ones, improved the embedding capacity by at least 100%.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multicolumn{2}{c}{**Payload (bit)**} & \multicolumn{2}{c}{**32**} & \multicolumn{2}{c}{**48**} & \multicolumn{2}{c}{**56**} & \multicolumn{2}{c}{**63**} \\ \hline \multirow{2}{*}{**Perceptual Similarity**} & **PSNR** & \multirow{2}{*}{**SSIM**} & **PSNR** & **PSNR** & **PSNR** & **PSNR** & **PSNR** & **PSNR** & **PSNR** \\  & **(dB)** & & **(dB)** & & **(dB)** & & **(dB)** & **(dB)** & **(dB)** & **(dB)** & **(dB)** \\ \hline \multirow{3}{*}{[PERSON]} & \(T=2,M=1\) & 69.09 & 1.0000 & 66.65 & 1.0000 & 65.55 & 1.0000 & 64.96 & 1.0000 \\  & \(T=2,M=2\) & 59.08 & 0.9999 & 55.85 & 0.9997 & 54.88 & 0.9996 & 54.39 & 0.9996 \\  & \(T=2,M=3\) & 51.58 & 0.9992 & 49.85 & 0.9986 & - & - & - & - \\ \hline \multirow{3}{*}{Barbara} & \(T=2,M=1\) & 66.44 & 0.9999 & 65.27 & 0.9999 & 64.69 & 0.9999 & 64.29 & 0.9999 \\  & \(T=2,M=2\) & 57.25 & 0.9993 & 55.53 & 0.9991 & 54.73 & 0.9990 & 54.39 & 0.9990 \\  & \(T=2,M=3\) & 51.72 & 0.9980 & 49.97 & 0.9973 & 49.44 & 0.9969 & - & - \\ \hline \multirow{3}{*}{Lena} & \(T=2,M=1\) & 66.43 & 0.9999 & 65.26 & 0.9999 & 64.32 & 0.9999 & 63.73 & 0.9999 \\  & \(T=2,M=2\) & 56.84 & 0.9992 & 55.04 & 0.9988 & 53.89 & 0.9984 & 53.51 & 0.9982 \\  & \(T=2,M=3\) & 51.16 & 0.9971 & 49.49 & 0.9955 & - & - & - & - \\ \hline \multirow{3}{*}{Peppers} & \(T=2,M=1\) & 67.52 & 0.9999 & 64.98 & 0.9999 & 63.49 & 0.9998 & 62.99 & 0.9998 \\  & \(T=2,M=2\) & 57.22 & 0.9993 & 56.05 & 0.9992 & 55.13 & 0.9990 & 54.59 & 0.9988 \\ \cline{1-1}  & \(T=2,M=3\) & 52.62 & 0.9982 & 50.76 & 0.9970 & - & - & - & - \\ \hline \hline \end{tabular}
\end{table}
Table 2: Perceptual similarity for different test images (including Baboon, Barbara, Lena, and Peppers) at different bin widths, thresholds, and capacities.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{2}{c}{**Payload (bit)**} & **32** & **48** & **56** & **63** \\ \hline \multirow{4}{*}{[PERSON] et al. [13]} & embedding range & [0.3\(A\),1.7_A_] & [0.3\(A\),1.7_A_] & - & - \\  & \(T\) & 2 & 6 & - & - \\  & \(M\) & 2 & 2 & - & - \\  & bins’ number & 64 & 96 & - & - \\ \hline \multirow{4}{*}{[PERSON] et al. [17]} & embedding range & [0,255] & [0,255] & - & - \\  & \(T\) & 2 & 4 & - & - \\  & \(M\) & 3 & 2 & - & - \\  & bins’ number & 64 & 96 & - & - \\ \hline \multirow{4}{*}{Scheme 1 [18]} & embedding range & [15,244] & [15,244] & [15,244] & [15,244] \\  & \(T\) & 2 & 1.5 & 1.25 & 1.5 \\ \cline{1-1}  & \(M\) & 2 & 2 & 2 & 2 \\ \cline{1-1}  & bins’ number & 64 & 96 & 112 & 126 \\ \hline \multirow{4}{*}{Scheme 2 [18]} & embedding range & [15,244] & [15,244] & [15,244] & [15,244] \\  & \(T\) & 3 & 2+sqrt(0.5) & 2.5 & 37/16+sqrt(0.5) \\ \cline{1-1}  & \(M\) & 2 & 4 & 8 & 4 \\ \cline{1-1}  & bins’ number & 64 & 64 & 64 & 84 \\ \hline \multirow{4}{*}{The proposed} & embedding range & [0,255] & [0,255] & [0,255] & [0,255] \\  & \(T\) & **2** & 2 & 2 & 2 \\ \cline{1-1}  & \(M\) & **2** & 2 & 2 & 2 \\ \cline{1-1}  & bins’ number & **32** & 48 & 56 & 63 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Parameter settings for different algorithms.  
Figure 4: The original images, the watermarked images, and their difference for [PERSON] and [PERSON] (\(M=2\), \(T=2\), and \(C=63\)). (**a**) [PERSON] (original); (**b**) [PERSON] (watermarked); (**c**) [PERSON] (residual); (**d**) [PERSON] (original); (**e**) [PERSON] (watermarked); (**f**) [PERSON] (residual).