  Image steganography camouflages secret messages in images by tampering image
contents. There is a natural desire for hiding maximum secret information with
the least possible distortions in the host image. This requires an algorithm
that intelligently optimizes the capacity keeping the required imperceptibility
of the image. This paper presents an image steganography scheme that preserves
an adaptively chosen block of dominant coefficients from each Discrete Cosine
Transform coefficients, whereas the rest of the coefficients are replaced with
normalized secret image pixel values. Secret image pixel value are normalized
in an adaptively chosen range. Embedding such kind of normalized data in
adaptively chosen non-square L- shaped blocks utilize maximum embedding space
available in each block that consequently results in maximizing payload
capacity, while maintaining the image quality. This scheme achieved payload
capacity up to 21.5 bit per pixel (bpp), while maintaining image quality of
38.24 dB peak signal to noise ratio.
