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AssigneeDigimarc Corporation
InventorsGeoffrey Rhoads, Clay Davidson, Anthony Rodriguez
Estimating the term…
Embedding a watermark in an image by changing selected DCT coefficients in the blocks and macro blocks of coefficients which represent the image. The changes in the blocks that comprise each macro block are done in a coordinated manner so that the phase of the watermark signal is preserved across the block boundaries. By preserving the phase across block boundaries, a detectable grid is formed which can be used as an orientation and scaling grid. Furthermore, by preserving the phase across block boundaries the visual artifacts introduced by the watermark are minimized. The bit rate of the image signal is preserved by maintaining a count (referred to as the cumulative change count) that represents the amount that the bit rate has been increased by changes in coefficients less the amount that the bit rate has been decreased by changes in the coefficients. If at any time the cumulative change count exceeds a pre-established limit, coefficient changes that decrease the cumulative change count continue; however, coefficient changes that increase the cumulative change count are suspended. The suspension of coefficient changes that increase the cumulative change count continues until the cumulative change count falls below the pre-established limit.
A method for adding a multibit watermark to an image comprising, generating DCT (Discrete Cosine Transform) coefficients representing said image, said
A system for adding a multibit watermark to an image comprising,
A method of embedding a watermark into an image comprising,
A method of introducing a watermark into a stream of bits representing variable length codes without changing the bit rate of said stream of bits comprising, maintaining a cumulative change amount which indicates the amount of the positive and negative changes which are made to said codes, suspending any positive changes if the cumulative change amount exceeds a pre-established limit, whereby the bit rate of said stream of bits is maintained constant.
A system for introducing a watermark into a stream of bits representing variable length codes without changing the bit rate of said stream of bits comprising, means for maintaining a count of the amount of positive and negative changes which are made to said codes, means for suspending any positive changes if a pre-established limit is exceeded, whereby the bit rate of said stream of bits is maintained constant.
A method for adding a multibit watermark to an image comprising,
An image processing method that includes steganographically encoding an input image to embed a multi-bit code therein, generating DCT (Discreet Cosine Transform) coefficients representing said image, said coefficients being arranged into primary size blocks, arranging said DCT coefficients into macro blocks, each containing four of said primary size blocks, changing the coefficients in each block to encode therein a watermark in said image, the direction of change of said coefficients being such that the sinusoids created by said changes are continuous across the primary blocks in said macro blocks, whereby said watermark signals can be used to both carry data and to form an orientation and calibration grid.
A method of embedding a watermark in a stream of coded symbols that represent a series of images by selectively increasing or decreasing the values of said symbols, said method comprising,
A method of embedding a watermark in a series of bit which represent an image without increasing the entropy of said image beyond a pre established limit, comprising the steps of:
A method of embedding a watermark in a series of bit which represent an image without increasing the entropy of said image beyond a pre established limit comprising the steps of:
Dependencies are inferred from the claim text.