Watermark embedding and extracting method and embedding hardware structure used in image compression system

A watermark extracting method used in an image compression system, comprising:

• partitioning an image to be tested X* into a plurality of sub-image blocks, wherein each sub-image has an 8×8 dimension;
• performing a discrete cosine transformation on each sub-image block to obtain a plurality of data, and using zigzag coding for sorting the data from low frequency to high frequency;
• extracting a watermark signal energy W*;
• using a relationship of Z=W×W*/M to obtain a correlated value Z of a watermark contained in the image to be tested X*, wherein W is a value of the embedded watermark, and M is a quantity of the embedded watermark;
• and
• determining that the image to be tested X* contains the watermark when the correlated value Z is larger than a critical value Sz, where the critical value Sz can be expressed by
• 8 S z = α _ 3 ⁢ M ⁢ ∑ i = 1 M ⁢ ⁢ W i * ,
• where {overscore (α)} is an average weighted value.

A watermark embedding structure used in an image compression system, comprising:

• a discrete cosine transformation register, to store a plurality of data obtained by discrete cosine transformation;
• a quantization table ROM, to store a plurality of quantized values;
• a first comparator, coupled to the quantization table ROM to receive the data and the quantized values and the data, and to compare the quantized values and the data to output a plurality of quantized data;
• a first register, to store a first configuration value;
• a second register, to store a second configuration value;
• a second comparator, coupled to the first comparator, the first register, and the second register to receive the quantized data, the first and second configuration values, and to compare the quantized data, the first configuration value and the second configuration value to output a weighted value for each of the quantized data;
• a multiplier, coupled to the second comparator to receive the weighted values and to multiply the weighted values with a watermark value to output an embedded watermark value;
• and
• an adder, coupled to the discrete cosine transformation register and the multiplier to receive and add the embedded watermark value and the data to output an embedded watermark data;
• wherein the embedded watermark data is stored in the discrete cosine transformation register and then output thereby.

A watermark embedding hardware structure used in an image compression system, comprising:

• a discrete cosine transformation register, to store a plurality of data which have been processed by a discrete cosine transformation module;
• a classification detection system, coupled to the discrete cosine transformation register to receive the data, and using classification to output a weighted value corresponding to each of the data;
• and
• a watermark embedding apparatus, coupled to the classification detection system to receive the weighted value and a watermark value, and to multiply the weighted value and the watermark value to obtain an embedded watermark value, and receiving one of the data which is to be embedded with the embedded watermark value and adding the one of the data with the embedded watermark value to output an embedded watermark data;
• wherein the embedded watermark data is stored in the discrete cosine transformation register and is then output thereby.