Based on the contrast sensitivity characteristics of human vision system and image features
a method was proposed to calculate the just noticeable difference thresholds of different frequencies of spectrum image. The thresholds was utilized to determine the watermark embedding and extraction. The watermarking scheme was designed
validated by experiment
and tested by attack
the results show that the peak signal noise ratio are all larger than 30 dB when JPEG compression quality factor is bigger than 30%
which indicates that the watermarks are well concealed. Normalized correlation value could still get to 0.653 9 under the case of compression quality factor of 20%
and the extracted watermarks could still clearly be seen intuitively.