# Data Hiding Method for Color AMBTC Compressed Images Using Color Difference
## 5 Experimental Results
Our proposed method compresses to 7 bits for each of three quantization levels. In terms of image quality, it is shown that the proposed AMBTC is superior to the traditional CAMBTC in the case of PSNR, SSIM, and CD. It is shown that the proposed color AMBTC represents the original image more faithfully than the existing method. In other words, it may know that using three quantization levels is good in the aspect of image quality rather than that of using two quantization levels. Meanwhile, it shows that the CD reflects most of the SSIM and PSNR measurements. However, some results of CD show that the SSIM and PSNR values do not have a proportionally full relationship. For example, CDs of Baboon images are 29.7421 and 26.1272, which have a large gap, but in terms of SSIM and PSNR, the gap is not large. It is reflecting another aspect of the human visual system that the existing PSNR and SSIM cannot measure. Figure 7 visually compares the Lena image generated from the traditional CAMBTC and the color AMBTC method we proposed. When the images (b) and (c) are enlarged, it can be seen that the (c) image has a clearer hat brim than the (b) image. In terms of image quality, it is natural that the lower the compression ratio, the better the image quality. However, our proposed method improved such limitations. In Table 2, EC denotes embedding capacity (bits) for the threshold \(T\). Naturally, as the value of \(T\) increases, the number of bits increases, and the CD increases. Here, \(O\) denotes an original image, and \(S\) denotes a stego(marked) image contained data. The difference between PROPOSE #1 and #2 is whether 16 bits are hidden or 32 bits are hidden in the common bitmap \(M\), i.e., the first case is a method of concealing 1 bit in each pixel of the bitmap \(M\), and the second case is a method of directly concealing 2 bits in each pixel of the common bitmap \(M\). In the given three methods, it can be known that when \(T\) increases, EC and CD increase simultaneously. PROPOSE#1 has the lowest CD until \(T\) is 10. On the other hand, \(T\) increases, it is PROPOSE#2 that provides the highest EC. CAMBTC \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**CAMBTC (96 Bits) 2Q/B**} & \multicolumn{4}{c}{**PROPOSED (95 Bits) 3Q/B**} \\ \cline{2-7}  & \(\mathbf{CD_{t}(O-M)}\) & **SSIM** & **PSNR** & \(\mathbf{CD_{p}(O-M)}\) & **SSIM** & **PSNR** \\ \hline Lena & 11.5419 & 0.9887 & 37.8912 & 10.6977 & 0.9914 & 39.6064 \\ Pepper & 12.4374 & 0.9882 & 37.4795 & 12.2976 & 0.9891 & 38.476 \\ Airplane & 10.3398 & 0.9346 & 37.1915 & 8.5637 & 0.9312 & 40.4584 \\ Lake & 18.4897 & 0.9618 & 34.0499 & 17.0456 & 0.9623 & 35.316 \\ Baboon & 29.7421 & 0.9253 & 31.1472 & 26.1272 & 0.9322 & 32.2806 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of the quality between the tradition color AMBTC and the proposed AMBTC. Figure 7: Comparison of original Lena, traditional CAMBTC, and the proposed CAMBTC’s images. shows weak performance in terms of EC or CD. The performance of the methods is derived from the difference between the quality of the initial cover image and the EC of the marked image. Table 2 shows the differences. The quality of the initial cover image must be good enough to keep the quality when using the appropriate DH method afterward. Figure 8 shows the relationship between CD and hidden bits measured using the three DH methods for four images. For Lena (a), PROPOSE#1 is better than the other two methods until bits are 425,000. Also, PROPOSE#1 and #2 show superior performance in terms of CD than CAMABC in the entire x-axis. In Pepper (b), there is a little difference in CD in three methods up to the initial 125,000 bits, and then CD is increased in the range, \(x\)-axis: 125,000\(\sim\)300,000. The CD is decreased in the range, \(x\)-axis: 300,000\(\sim\)425,000. Also in (b), the CD of PROPOSE # 2 appears to outperform CAMBTC in the entire \(x\)-axis range.