## 4 Experimental Results
### Peak Signal to Noise Ratio (PSNR) Analysis on Various Embedding Levels  
In this section, we evaluated the visual quality of the proposed method at different embedding rates to verify whether the proposed method has consistent performance of visual quality at various embedding levels. The graphical representation of PSNR values of images for different sizes of secret bits are shown in Figure 5a-f. The methods developed by [PERSON] et al. [7], [PERSON] et al. [11], and [PERSON] et al. [15] are compared with the proposed method to observe the differences in performance. For the Gray21 image, the capacity vs PSNR graph is as shown in Figure 5a. Once the embedding capacity is high, i.e., 500,000 bits, the proposed method obtained the highest PSNR of 43.17 dB, while the compared methods achieved lower PSNR, i.e., 41.70 dB ([PERSON] et al.), 40.20 dB ([PERSON] et al.), and 39.30 dB ([PERSON] et al.). Similarly, if the embedding bits are 250,000, again the proposed method achieved a higher PSNR (44.40 dB) while the others obtained 42.50, 41.90, and 40.23 dB, respectively. Furthermore, if the embedding capacity is around 50,000 bits, the proposed method has far better PSNR up to 48.65 dB as compared to existing methods.  
From Figure 5b of the Motion image, the proposed method obtained the maximum PSNR 43.21 dB at 500,000 bits embedding. However, the compared methods achieved low PSNR as compared to the proposed method, i.e., [7] 41.39 dB, [11] 40.45 dB, and [15] 38.96 dB at the same 500,000 bits. Similarly, the proposed method achieved the maximum PSNR (48.50 dB) at 50,000 bits for Ruler image in Figure 5c and 48.20 dB for Stream image in Figure 5d.  
In the same way, from Figure 5e, the proposed method obtained the highest PSNR 43.19 dB at 500,000 bits while the compared methods recorded low PSNR, i.e., 40.89 dB [7], 39.93 dB [11], and 39.05 dB [15] for the Tank image. In Figure 5f, the highest PSNR achieved by previous methods is 44.78 dB for [PERSON] et al., 46.52 dB for [PERSON] et al., and 42.67 dB for [PERSON] et al., while the proposed  
Figure 5: Comparison graphs for PSNR versus various embedding capacity from the USC-SIPI [24] dataset. The figures are (**a**) Gray21, (**b**) Motion, (**c**) Ruler, (**d**) Stream, (**e**) Tank, and (**f**) Truck.  
method obtained the highest PSNR of 48.53 dB for the Truck image. On average, PSNR results at the lowest embedding capacity are obtained by the methods: 43.99 dB [7], 45.10 dB [11], 42.10 dB [15], and the proposed method with 48.43 dB. At 500,000 bits, the proposed method recorded the highest PSNR with 43.19 dB followed by [PERSON] et al. with 41.16 dB, [PERSON] et al. with 40.14 dB, and [PERSON] et al. with 39.01 dB. Therefore, the proposed method yields the highest PSNR at different embedding capacities against [PERSON] et al., [PERSON] et al., and [PERSON] et al.  
Consequently, from experiments, the proposed method outperformed the compared methods; it was proven that the proposed method retains high visual imperceptibility irrespective of embedding rates. The reason behind achieving the better results depends on the maximum number of bits mapping strategy while reducing the number of bits modification into the pixel.