An image processor unit minimizes image-quality degradation that can be caused
by the addition of predetermined information to an image and that enables the predetermined
information to be added to the image so that embedded information can be accurately
extracted. The image processor unit includes an input unit for inputting the image;
a plurality of quantization-threshold setting unit, of which occurrence probability
distributions are different from one another, for setting quantization thresholds
in terms of probability; a control unit for controlling a regularity for selection
of the plurality of quantization-threshold setting unit in units of a predetermined
image region according to the predetermined information; and a quantizing unit
that uses quantization thresholds set by the quantization-threshold setting unit
and thereby quantizes the image according to an error diffusion method.
