Simple Possibilities of 2D DCT Application in Digital Monochrome Image Cryptography

Any images are result of some previous photochemical or photoelectric processes. The main image information content, from the HVS viewing point, is focused in whole colorimetric (color hue and saturation, brightness, contrast) and spatial (resolution and sharpness) information. The aim for all conventional or standard image-processing methods is to improve colorimetric and spatial image parameters in relation with maximal information content. Sometimes may be useful an application of non-conventional or non-standard image processing procedure on an image and employ the image as a non-visible texture, [1] - [4], or another binary image (watermark) carrier, [5]. The problems discussed in this contribution are focused on the analysis and description of unconventional cryptographic methods, based on 2D DCT application, for inserting non-visible binary watermarks into the 2D image plane. In this relation there are shortly described methods for decoding the watermark and are presented selected obtained results.