COMPARATIVE STUDY OF STEGANOGRAPHY ON GRAY, INDEXED, COLOUR AND BLACK & WHITE IMAGES BY EQUAL / NEAR EQUAL VALUE PIXEL REPLACEMENT POINT OPERATIONS

In this paper, we consider four types of images namely gray scale, indexed, colour and black & white images and apply steganogrphic techniques by embedding text of 512 bytes in each of these images. Three simple pixel replacement techniques like equal or nearly equal pixel replacement in each column, equal or nearly equal in pixel replacement in entire image, random pixel replacement and natural number increment pixel replacement methods are adopted. The actual, stego and the extracted images are shown explicitly. The Mean Square Error (MSE) and Peak to Signal Noise Ratio (PSNR) indices have been computed in each case. The histograms for the computed values of MSE and PSNR indices are drawn. At the end, we have given an introduction to steganography in an audio file.