35 results about "Jpeg2000 compression" patented technology

The invention discloses a random computing method for an importance degree of a wavelet coefficient of a two-dimensional image. The present method is very rough and is generally used for only dividing foreground and background coefficients or appointing one importance degree to each code block. The random computing method comprises the following steps: firstly, initializing alpha as a 0 matrix and generating a random matrix r, wherein the row number and the line number are consistent with beta and the elements are uniformly distributed on a coordinate (-1, 1); defining beta'=sgn(r)*beta and performing wavelet conversion W on beta', thereby obtaining alpha': alpha'=W(beta'); finally, updating alpha:alphap=max(alphap, absolute value of alphap') and performing p0 on each position; and if alpha no longer changes, ending and outputting alpha. According to the random computing method provided by the invention as a middle step of a JPEG2000 implicit ROI encoding process, the importance degree of each element on an image space is converted into the importance degree of each coefficient on a wavelet domain. According to the random computing method provided by the invention, the more accurate control on the ROI area and importance degree of a JPEG2000 compressed image is realized.

The invention provides a semi-fragile digital watermaking system based on non-redundant Contourlet conversion, which can complete watermak embedding by regulating the magnitude relationship of parent-child coefficients. By utilizing the semi-fragile characteristic of the parent-child coefficients, the invention can get robustness to JPEG compression, JPEG 2000 compression, Gaussian noise adding, Gaussian filtering and contrast stretching operation, but has vulnerability to replication and pasting baleful operation with change of work content information. An experimental result shows that the semi-fragile digital watermaking system of blind detection proposed by people can ensure that certification and location of tampering a region are accurately realized under the conditions of the false alarm rate being lower than 6.5 percent and MDR being lower than 1 percent. By utilizing the parent and child relationship of WBCT region, the system enhances the detection accuracy rate of tampering the region when being in associated attack by the baleful operation and non baleful operation.