Abstract

When RGB images are processed for the implementation of steganographic algorithms, it is important to study the quality of the cover and retrieved images, since it typically used digital filters, reaching visibly deformed images. The discrete wavelet transform is useful for adjusting the stego- image quality, because one of their principal qualities which are able to analyze different frequency levels (multi-resolution analysis). By decomposing the image using the discrete wavelet transform, we obtain sub-images representing different levels of frequencies, in each of these sub-bands can expand or contract the obtained adjusting sub image well as possible to a desired quality. There by avoiding one of the main problems of steganography: distortion of stego-image. When a steganographic algorithm is employed, numerical calculations performed by the computer cause errors and alterations in the processed images, so we apply a scaling factor depending on the number of bits of the image to adjust these errors.

Key words: Steganographic algorithms, RGB images, scaling factor, wavelet.