M.Barni, F. Bartolini, V. Cappellini, A. Piva. "A DCT-Domain
System for Robust Image Watermarking",
Signal Processing, vol.66, pp 357-372, 1998.

V. Fotopoulos, A.N. Skodras, "A Subband DCT approach to
image watermarking", X European Signal Processing Conference,
September 4-8, 2000, Tampere, Finland

parameters:
for starting coefficient reasonable values for the dct and hartley schemes
and this kind of dimensions is around 5000-20000, for the watermark length 10000-50000,
and seed/key should be in the range 1-1000 so that the output file of the testing module
gives a right similarity diagram

for the subband dct version, things change corresponding to coefficients
because the bands' sizes are 1/4 of the original image's size.
starting coef should be between 3000-5000 and length 10000-20000
for the alpha parameter i use 0.2 for all bands except LL for which i use
0.1