Insertion and extraction of a message in an image
AssigneeCanon Kabushiki Kaisha
InventorHervé Le Floch
Life of this patent
Estimating the term…
Abstract
The invention concerns a method of inserting a message in an image, the message comprising binary symbols which are each referenced by an index, characterized in that it comprises, for a coefficient (Yn) of the image, the steps of: determining (E9) a watermarked value (Y′n) of the coefficient, according to the binary value (b) of a symbol of the message and according to the index (i) of the symbol, inserting (E11) the watermarked value in place of the value of the coefficient.
Claims24
A method of inserting a message in an image, the message comprising binary symbols which are each referenced by an index, comprising, for a coefficient of the image, the steps of:
- determining a watermarked value of the coefficient, according to the binary value of a symbol of the message and according to the index of the symbol in the message, wherein the index of the symbol is determined from a value of the coefficient of the image, and
- inserting the watermarked value in place of the value of the coefficient, wherein the determination of a watermarked value of the coefficient comprises:
- selecting a modified value of the coefficient,
- determining a symbol index, according to the modified value and a first predetermined function,
- determining the value of the message symbol corresponding to the determined symbol index, and
- verifying that the value of the message symbol previously determined corresponds to the transformation of the modified value by a second predetermined function.
A method of extracting a message from an image, comprising the steps of:
- for each coefficient of the image, calculating a symbol index and a binary value, both according to a value of the coefficient,
- totaling the number of each of the binary values obtained for each of the symbol indexes, and
- allocating to each symbol index the binary value having the largest total.
A method of extracting a message from an image, comprising the steps of:
- for a coefficient of the image, calculating a symbol index according to a value of the coefficient, for each coefficient of the image,
- calculating a first and a second value, both according to a value of the coefficient, for each coefficient of the image,
- first totaling of the absolute values of the differences between the value of the coefficient and the first value, for each symbol index, and
- second totaling of the absolute values of the differences between the value of the coefficient and the second value, for each symbol index,
- allocating to each symbol index a binary value according to the smallest total amongst the first and second totals.
A device for inserting a message in an image, the message containing binary symbols which are each referenced by an index, comprising:
- means for determining a watermarked value of a coefficient of the image, according to the binary value of a symbol of the message and according to the index of the symbol, wherein the index of the symbol is determined from a value of the coefficient of the image, and
- means for inserting the watermarked value in place of the value of the coefficient wherein the means of determining a watermarked value of the coefficient comprise:
- means for selecting a modified value of the coefficient,
- means for determining a symbol index, according to the modified value and a first predetermined function,
- means for determining the value of the message symbol corresponding to the determined symbol index, and
- means for verifying that the value of the message symbol previously determined corresponds to the transformation of the modified value by a second predetermined function.
A device for extracting a message from an image, comprising:
- means for calculating, for each coefficient of the image, a symbol index and a binary value, both according to a value of the coefficient,
- means for totaling the number of each of the binary values obtained for each of the symbol indexes, and
- means for allocating to each symbol index the binary value having the largest total.
A device for extracting a message from an image, comprising:
- means for calculating, for each coefficient of the image, a symbol index according to a value of the coefficient,
- means for calculating first and second values according to the value, for each coefficient of the image,
- means for first totaling of the absolute values of the differences between the value of the coefficient and the first value, for each symbol index,
- means for second totaling of the absolute values of the differences between the value of the coefficient and the second value, for each symbol index,
- means for allocating to each symbol index a binary value according to the smallest total amongst the first and second totals.
Dependencies are inferred from the claim text.