Ideal Steganography Scenario: Calculation of Capacities of Carrier Images, OPA Method in Frequency-Based Steganography

In this study, digital image steganography, a branch of steganography, and DCT (Discrete Cosine Transform) and DWT (Discrete Wavelet Transform, frequency-based steganography methods that are a sub-branch of it, are mentioned. Methods such as MSE (Mean Squared Error), PSNR (Peak Signal Noise Ratio) which are performance calculation parameters of steganographic methods are explained and the methods of calculating image capacity like KL-Divergence, JS-Divergence and QTS (Quard Tree Segmentation) for increasing the values of these parameters are mentioned. This study explains the OPAP (Optimum Pixel Adjustment Process) method, which allows the existing capacity in the pictures to be further increased, in detail and provides an ideal steganography scenario. Here, we made use of the ability of the DWT to extract low frequency and bands suitable for data hiding and the use of the LSB method by obtaining the feature coefficients of DCT in these bands.. In addition, this scenario has been tried and consequently reached the result that the images with higher data concealment capacity than QTS have higher PSNR values