Patent ID: 7197163

Claim:
A watermark embedding method based on discrete cosine transformation (DCT) subband image characters to generate a frequency image from an original image using an 8*8-block DCT and to embed a binary watermark image into a subband image of the frequency image, the method comprising the steps of: setting the values of a first experience parameter TH 1 and a second experience parameter TH 2 ; obtaining the frequency image converted from the original image and a series (A 1 . . . An) of the binary watermark image; extracting in order a 3*3 macro-block of the frequency image and read in order the numerical value An of the binary watermark image; and analyzing the type of the numerical value being read from the binary watermark image and performing a DCT parameter setting for an embedded block, which further includes the steps of: computing a plurality of sets of parameter combinations of the embedded block in the 3*3 macro-block and comparing the parameter combinations with the DCT parameter error of the embedded block; adding the parameter combination with the least error and TH 2 to replace a DCT parameter of the subband image position in the embedded block when the least error is less than TH 1 and An is one of 1 or 0; and subtracting TH 2 from the parameter combination with the least error to replace a DCT parameter of the subband image position in the embedded block when the least error is less than TH 1 and An is the other of 1 or 0.