Patent ID: 6993151

Claim:
A watermark embedding method used in an image compression system, comprising: partitioning an original image into a plurality of 8×8 sub-image blocks B k , where k=1, 2, 3, . . . , n, and n is a positive integer; performing a discrete cosine transformation on each sub-image block; using classification to perform texture and luminance analysis on each sub-image block to generate an analysis value, and categorizing each sub-image block into three levels, including: when number {intF k (u,v)/Q k (u,v))≠0}<T 2 and F k (0,0)<T 1 , the sub-image block B k is defined as class 1 to indicate dark luminance and insignificant texture characteristics; when number {intF k (u,v)/Q k (u,v))≠0}>T 2 and F k (0,0)>T 1 , the sub-image block B k is defined as class 3 to indicate bright luminance and significant texture characteristics; when the sub-image block B k is neither class 1 nor class 3, the sub-image B k is defined as class 2 to indicate luminance and texture characteristics between class 1 and class 3; wherein F k (0,0) indicates a low frequency value (DC) obtained by performing a discrete cosine transformation on each sub-image block B k , F k (u,v) indicates a high frequency value (AC) obtained by performing a discrete cosine transformation on each sub-image block B k , where u, v≠0, Q(u,v) is a quantized value, T 1 is a value in low frequency, and T 2 is a non-zero number in high frequency; determining an image characteristic for each sub-image block and an appropriate weighted value α k corresponding to the image characteristic; multiplying the weighted value and a watermark value, and obtaining a data F k * of a watermark embedded into each sub-image block corresponding to a fixed position of the sub-image block from the following equation: F k * = { F k ⁡ ( u , v ) + ( α k × x i ) , 3 ⁢ k < i < ( 3 ⁢ k + 1 ) , ( u , v ) ⁢ ⁢ ε ⁢ ⁢ { ( 0 , 1 ) , ( 1 , 0 ) , ( 1 , 1 ) } F k ⁡ ( u , v ) , ⁢ others ( 1 ) where x i is an embedded watermark value; and generating a JPEG file by quantizing and encoding the embedded watermark data.