1) The document discusses and compares different image compression techniques, specifically DCT and fractal compression.
2) Fractal compression works by finding self-similar patterns within an image during encoding, but can have a long computation time. DCT transforms an image into frequency coefficients that can be quantized for compression.
3) The document reviews previous work combining DCT and fractal compression with steganography and encryption to improve hiding capacity, imperceptibility, and security against subterfuge attacks. However, prior methods had limitations like low data hiding amounts or lack of protection for compressed data.