Methods for emitting and receiving a mask for tattooing an image

Abstract

The invention relates to a method for emitting data representative of a mask for watermarking an image included in a set comprising at least that image, comprising the following steps: - a step of defining (E1) a geometric distribution, comprising R two-dimensional regions, by means of at least one segmentation of a luminance component constructed on the basis of at least one image of said set, - a step of assigning (E2) a coefficient to each two-dimensional region, - a step of sending (E3) data representative of the mask comprising at least a portion of the coefficients. A method for receiving data representative of a mask is also described. Figure for the abstract: Fig. 1

Description

Title of the invention: Methods for transmitting and receiving a mask for watermarking an image Technical field of the invention

[0001] The present invention generally relates to the technical field of digital watermarking of an image or a video sequence.

[0002] It relates in particular to a method of transmitting data representative of a mask for watermarking an image and an associated reception method. State of the art

[0003] The technique of digital watermarking of audiovisual content consists of inserting information into it, called a watermark or mark. One of the aims of this technique is, for example, to identify the author of the watermarked audiovisual content.

[0004] In the context of video on demand (VoD), audiovisual content can be analyzed in advance and a digital watermarking of the audiovisual content can be carried out on the receiving terminal. This configuration can be used to create marks adapted to the audiovisual content, by the use of perceptual masks. The concept of perceptual mask is for example described in the article "Efficient Spatial Image Watermarking via New Perceptual Masking and Blind Detection Schemes", by Karybali in IEEE Transactions on Information Forensics and Security (June 2006). Perceptual masks are constructed from activity information in the audiovisual content and make it possible to adjust the transparency of the inserted marks. Transparency characterizes the way in which the insertion of the mark alters the perception of the audiovisual content read by a user, and contributes to the quality of the watermarked video.

[0005] In the case where the digital tattoo is carried out on the receiving terminal, the size of the data sent for the tattoo represents an important parameter in the compromise sought between transmission efficiency and watermark quality. Presentation of the invention

[0006] In this context, the present invention proposes a method for transmitting data representative of a mask for watermarking an image (of size MoxNo pixels) included in a set comprising at least this image, the method comprising the following steps: - a step of defining a geometric distribution, comprising R two-dimensional regions, by means of at least one segmentation of a luminance component constructed on the basis of at least one image of said set, - a step of assigning a coefficient to each two-dimensional region, - a step of sending data representative of the mask M comprising at least part of the coefficients.

[0007] By segmenting into two-dimensional regions and assigning a coefficient to these two-dimensional regions, a segmented perceptual mask is defined which offers the possibility of sending a reduced quantity of information to carry out the watermarking of the image on a receiving terminal while guaranteeing the effectiveness of the watermarking.

[0008] In one embodiment, the coefficient is determined based on statistical parameters of the image I in the two-dimensional region.

[0009] For example, the coefficient is calculated as a function of coefficients contained in a perceptual mask (of size MoxNo pixels) and relative to the two-dimensional region.

[0010] In one embodiment, the statistical parameters of the image are determined based on at least one image processing method selected from a Laplace filter, a variance calculation, a Fourier transform calculation or a local binary pattern calculation.

[0011] In one embodiment, the data representative of the mask sent in the sending step only comprise the coefficients respectively assigned to a fraction of the pixels of the mask during the allocation step.

[0012] In one embodiment:

[0013] - the allocation step comprises the formation of a segmented mask in which each pixel has as its value the coefficient assigned to the two-dimensional region comprising said pixel, - the method comprises a step of subsampling said segmented mask into a subsampled segmented mask comprising at least part of the coefficients, - the representative data sent in the sending step correspond to at least part of the coefficients.

[0014] In one embodiment, the data representative of the mask sent in the sending step comprises data defining at least a portion of said two-dimensional regions.

[0015] For example, the data defining at least a portion of said two-dimensional regions comprises a plurality of lists of points determining the closed contours of at least a portion of the R two-dimensional regions.

[0016] In one embodiment, the image belongs to a slice of images of a video packet.

[0017] In one embodiment: - during the definition step, the at least one segmentation comprises P segmentations Sp of P luminance components, each luminance component being constructed on the basis of one among P sequences of ECHp images of the video packet, said P ECHp image sequences having a length less than or equal to the length of the image slice, - the definition step further comprises the selection of a defined segmentation Sd from among the P segmentations Sp, the R two-dimensional regions being derived from the defined segmentation Sd, - during the allocation step, the coefficient is equal to the average of the values ​​of the pixels of the two-dimensional region of a defined mask Md determined on the basis of the sequence of images Ed corresponding to the defined segmentation Sd.

[0018] For example, during the definition step, the defined segmentation Sd among the P segmentations Sp corresponds to a minimum error among P calculated errors, for each sequence of images ECHp, between a reference perceptual mask of the sequence of images and a segmented perceptual mask of the sequence of images ECHp.

[0019] For example: - the pixels of a reference perceptual mask of an ECHp image sequence have as their value the minimum value of the corresponding pixels of perceptual masks calculated on the basis of each of the images of the ECHp image sequence, - each perceptual mask is calculated from statistical parameters of an image in the image sequence, - for each segmented perceptual mask of an ECHp image sequence, the pixels of each zone defined by the segmentation Sp (corresponding to the ECHp image sequence) have as their value the average of the values ​​of the pixels of the reference perceptual mask in said zone.

[0020] For example, the defined mask corresponds to the reference perceptual mask of the image sequence corresponding to the defined segmentation.

[0021] Another aspect of the invention relates to a method for transmitting data representative of a mask for watermarking an image (of size MoxNo pixels) comprising the following steps: - a step of defining a geometric distribution, comprising R two-dimensional regions, by means of at least one segmentation of the mask, - a step of assigning a coefficient to each two-dimensional region, - a step of sending data representative of the mask comprising at least part of the coefficients.

[0022] Another aspect of the invention relates to a method for receiving data representative of a mask (of size MoxNo pixels) for watermarking an image (of size MoxNo pixels) comprising the following steps: - a step of receiving data representative of a segmented mask (of size MxN pixels less than MoxNo pixels defined by a geometric distribution comprising R two-dimensional regions), said representative data comprising a plurality of coefficients (associated with at least part of the R two-dimensional regions), - a step of reconstructing the mask based on the coefficients, - a step of obtaining a weighted mark by applying the mask to a mark (of size MoxNo), - a step of watermarking the image by applying the weighted mark to the image.

[0023] In one embodiment, the step of reconstructing the mask comprises assigning the coefficients to pixel areas comprising at least one pixel.

[0024] In one embodiment: - the data representative of the segmented mask further includes data defining two-dimensional regions, - the mask reconstruction step includes plotting the two-dimensional regions based on the data defining the two-dimensional regions and assigning a coefficient to each of the two-dimensional regions.

[0025] In one embodiment:

[0026] - the data representative of the segmented mask further comprises a plurality of lists of points defining the closed contours of two-dimensional regions,

[0027] - the mask reconstruction step includes tracing the regions two-dimensional by means of the plurality of point lists and the assignment of a coefficient to each of the two-dimensional regions.

[0028] For example: - the image belongs to a slice of images of a video packet, - the mask is common to the images in the image slice.

[0029] Of course, the various features, variants and embodiments of the invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive. Detailed description of the invention

[0030] Furthermore, various other characteristics of the invention emerge from the appended description given with reference to the drawings which illustrate non-limiting forms of embodiment of the invention and where: - [Fig.l] represents the different stages of the method of transmitting data representative of a mask according to the invention; - [Fig.2] represents the different stages of a first embodiment of the method for transmitting data representative of a mask according to the invention; - [Fig.3] represents an example of perceptual mask, segmentation and reduced mask obtained by the first embodiment of the emission method according to the invention; - [Fig.4] represents the different steps of a second embodiment of the method for transmitting data representative of a mask according to the invention; - [Fig.5] represents the sub-steps of a step of the second embodiment of the transmission method according to the invention; - [Fig.6] represents the different stages of the method of receiving data representative of a mask according to the invention.

[0031] We are here in the context of video on demand (VoD) where audiovisual content can be analyzed in advance, but the solution proposed here can also be applied to other situations, for example to the television context by adapting the method according to the invention which will be described below. It can also be applied to the case of a single image.

[0032] In the following, the principle followed in the context of the present invention is presented with the final aim of watermarking, by a receiving terminal, a video sequence received by this receiving terminal. By "watermarking", it is meant the insertion of a pattern in each image contained in the video sequence. As will be described later, the pattern corresponds to a mark, for example a constant one modulated by a perceptual mask. The mark makes it possible, for example, to identify the author of the video sequence or the receiving terminal on which the video sequence was decoded. It is assumed that the video sequence has been selected by a user of the receiving terminal from a library of video sequences available on a server device. The server device then sends the selected video sequence to the receiving terminal in image packets ("chunks" in English) via a network such as the Internet or a third-generation telephone network.The images forming the selected video sequence have a size of MOxNO pixels. Each image packet is sent accompanied by metadata which will be used in particular for watermarking, by the receiving terminal, of the image packet.

[0033] A method of transmitting data representative of an MS mask for watermarking, by a receiving terminal, an image included in a video sequence received by this receiving terminal will be described.

[0034] The receiving terminal receives the video sequence in image packets. Each image packet is divided into K successive image slices. For example, the duration of the image packet is 10 seconds. For example, the duration of an image slice is 2 seconds. The data representative of the MS mask will be used for watermarking all the images in an image slice.

[0035] We consider a packet of images S of the video sequence received, accompanied by metadata MT, by the receiving terminal, and more particularly a slice of images T of this packet of images.

[0036] The method for transmitting data representative of the mask MS for watermarking the images of the image slice T comprises, as illustrated in [Fig.l], the following steps: - a step E1 of defining a geometric distribution RG, comprising R two-dimensional regions Zr, by means of at least one segmentation of a luminance component constructed on the basis of a reference image I of the image slice T, - a step E2 of assigning a coefficient MSr to each two-dimensional region Zr, - a step E3 of sending data representative of the mask M comprising at least part of the coefficients MSr.

[0037] In the following, the preparation of the MT metadata accompanying the image packet S will be described. This MT metadata is prepared prior to the transmission of the image packet S to the receiving terminal. The MT metadata described defines the mask M, but other metadata could be used in practice for other reasons.

[0038] [Fig.2] illustrates the steps constituting a first embodiment of the preparation of MT metadata.

[0039] In this first embodiment, the reference image I is for example the first image of the image slice T. In a variant, the reference image I corresponds to a change of scene identified in the image slice T.

[0040] In a step EOa, a perceptual mask is calculated in correspondence with the reference image I of the image slice T of the image packet S. By perceptual mask is meant a matrix of size MOxNO whose coefficients represent a measure of the activity of the corresponding reference image I. For example, the perceptual mask is calculated by applying a Laplace filter to the reference image I. In another example, a variance calculation can be carried out to obtain the perceptual mask. Other techniques, alone or in combination, can be used to obtain the perceptual mask, such as the detection of high-frequency zones (by measuring the local variance of the pixels, or by Fourier transform), the qualification of texture by local binary patterns. Preferably, the perceptual mask of a reference image is calculated on the basis of the three chromatic components of the reference image.

[0041] In a step E2a, a segmentation of the reference image I is carried out. Preferably, the segmentation is carried out on a luminance component of the reference image I. Different types of algorithm can be used to carry out the segmentation, for example the SLIC algorithm, the Watershed algorithm, the algorithm Quick Shift, or the Random Walker algorithm. The segmentation of the reference image I produces a partition into R two-dimensional regions Zr of a matrix of size MOxNO. This step E2a corresponds to the step E1 of defining the geometric distribution RG of the emission method according to the invention. The geometric distribution RG corresponds to the partition originating from the segmentation of the reference image I.

[0042] In a step E4a, a segmented perceptual mask is obtained in the following manner. The segmented perceptual mask is a matrix of size MOxNO whose coefficients are equal, for a two-dimensional region among the R two-dimensional regions of the partition obtained in step E2a, to the average of the values ​​of the perceptual mask in the two-dimensional region considered. This step E4a corresponds to the step E2 of assigning a coefficient MSr to each two-dimensional region Zr.More precisely, each coefficient MSr is equal to the average of the values ​​of the perceptual mask in the two-dimensional region Zr.

[0043] In a step E6a, the size of the segmented perceptual mask is reduced by subsampling, to form a reduced mask of size MxN pixels smaller than MOxNO pixels. For example, the reduced mask is 5 times smaller than the segmented perceptual mask in each dimension. In other words, MO is equal to Mx5 and NO is equal to Nx5. More generally, the dimensions of the reduced mask are smaller than those of the segmented perceptual mask. For example, MO is equal to kxM with k an integer strictly greater than 2 and NO is equal to k'xN with k' an integer strictly greater than 2. For example, the reduced mask has a size of 96x40 pixels. Then, the reduced mask is encoded in a dedicated format, for example in base64 format, for its transmission. The base64 format makes it possible to represent any binary data in alphanumeric characters.This format thus allows the transport of blocks of binary data via, for example, the http protocol using xml or html containers.

[0044] In this first embodiment, the MT metadata comprises the reduced mask.

[0045] [Fig.3] shows, for an image I, an example of perceptual mask MP, segmentation S of the luminance component of the image I, and of the reduced mask MR.

[0046] A subsequent step E8a consists of sending the metadata MT which includes the reduced mask, the pixel values ​​of which correspond to at least part of the coefficients MSr. This step E8a corresponds to the step E3 of sending the data representative of the mask MS.

[0047] We will now describe a second embodiment of the preparation of the MT metadata accompanying the image packet S received by the receiving terminal.

[0048] [Fig.4] illustrates the steps constituting this second embodiment of the preparation of MT metadata. The latter contain, as in the first embodiment, a segmented perceptual mask for each image slice included in the image packet. However, the segmented perceptual mask corresponding to an image slice is obtained by a different method described below. The preparation of the MT metadata is prior to sending the image packet S to the receiving terminal.

[0049] It is always assumed that the images in the image packet S have the size MoxNo pixels.

[0050] In a step EOb, a set of P samples are produced on the basis of P sequences of images ECHp included in the video packet S. By sample, we mean a pair (Pp,MPRp) formed of a reference perceptual mask MPRp and a partition Pp of a matrix of size MoxNo. Each sample corresponds to one of the P sequences of images ECHp.

[0051] Each of the samples is produced according to the following sub-steps illustrated in [Fig.5].

[0052] In a sub-step EObO, the temporal average of the luminance components of the images included in the sequence of images ECHp is calculated. This average is hereinafter referred to as the average luminance component IMp. In other words, the value of each pixel of the average luminance component IMp is the average of the values ​​of this same pixel in the different images of the sequence of images ECHp.

[0053] In a sub-step E0b2, the average luminance component IMp is segmented by a segmentation calculation Sp so as to produce a partition Pp formed of Rp two-dimensional regions Zrp.

[0054] In a sub-step E0b4, a reference perceptual mask MPRp of the image sequence ECHp is calculated. The reference perceptual mask MPRp is a matrix of size MoxNo and is calculated in the following manner. For each image Ipi of the image sequence ECHp, a perceptual mask Mpi is calculated from statistical parameters of the image Ipi. For example, the perceptual mask Mpi is calculated by applying a Laplace filter to the image Ipi. In another example, a variance calculation can be performed to obtain the perceptual mask Mpi. Other techniques, alone or in combination, can be used to obtain the perceptual mask Mpi, such as the detection of high-frequency areas (by measuring the local variance of the pixels, or by Fourier transform), the qualification of texture by local binary patterns. Preferably, the perceptual mask Mpi of an image Ipi is calculated on the basis of the three chromatic components of the image Ipi.

[0055] Each pixel of the reference perceptual mask MPRp has as its value the minimum value among the set of values ​​of the same pixel of the perceptual masks Mpi.

[0056] The result of step EOb is a set of P samples (Pp,MPRp). For each sample, a start time marker TMSp and an end time marker TMEp of the image sequence ECHp are kept in memory.

[0057] After step EOb, we consider a slice of images T of the packet of images S.

[0058] In a step E2b, the samples whose start timestamps TMSp and end timestamps TMEp are closest to the image slice T are retained. For example, the proximity criterion chosen may be that the difference between the start timestamp of the image slice and the start timestamp TMPs of the image sequence ECHp, or the difference between the end timestamp of the image slice T and the end timestamp TMEp of the image sequence ECHp are less than the duration of the image slice T.

[0059] In a step E4b, a sample from among the P' samples retained in step E2b is selected on the basis of the calculation of P' errors Errp. Each of the P' errors Errp corresponds to a difference between, for each sequence of images ECHp, the reference perceptual mask MPRp of the sequence of images ECHp and a segmented perceptual mask MPSp of the sequence of images ECHp. Each segmented perceptual mask MPSp is a matrix of size MOxNO. The pixels of a segmented perceptual mask MPSp have as their value, in a two-dimensional region Zrp of the partition Pp, the average of the values ​​of the pixels of the reference perceptual mask MPRp in said zone. An error Errp is for example calculated by applying the square root of the average of the squares of the difference of the pixel values ​​between the reference perceptual mask MPRp and the segmented perceptual mask MPSp. Alternatively, the P' errors Errp can be calculated using the L1 norm or a PSNR measure.

[0060] In a step E6b, a sample (Pd,MPRd) from among the P samples (Pp,MPRp) is selected on the basis of the P errors Errp. The sample (Pd,MPRd) corresponds to the minimum error Errp from among the P' errors Errp calculated in step E4b. The corresponding segmentation Sd is hereinafter referred to as defined segmentation Sd and the corresponding segmented perceptual mask MPSd is hereinafter referred to as defined segmented perceptual mask MPSd. This step E6b corresponds to step E1 of defining the geometric distribution RG, which includes the Rd two-dimensional regions Zrd as well as to step E2 of assigning a coefficient MSr to each two-dimensional region Zrd. More precisely, each coefficient MSr corresponds to the value of the pixels of the segmented perceptual mask MPSd in the two-dimensional region Zrd.

[0061] In a step E8b, the size of the defined segmented perceptual mask MPSd is reduced by subsampling, to form a reduced mask of size MxN pixels smaller than MOxNO. For example, the reduced mask is 5 times smaller than the segmented perceptual mask. For example, the reduced mask has a size of 96x40 pixels. Then, The reduced mask is encoded into a dedicated format, for example base64, for transmission. The MT metadata then includes the encoded reduced mask.

[0062] Alternatively, step E8b is replaced by a step E8b' taking place as follows. For each two-dimensional region Zrd of the partition Pd, a list of points Lrd determining the closed contour of the two-dimensional region Zrd is extracted. The number of points in the list of points Lrd can be adjusted in relation to the precision of the drawing of the closed contour. The extraction can for example be carried out by means of an image calculation function applied to the defined segmented perceptual mask MPSd. The metadata MT then comprise all the values ​​taken by the segmented perceptual mask MPSd in each of the two-dimensional regions Zrd as well as the plurality of lists of points Lrd, each value being associated with a list of points Lrd.

[0063] A subsequent step ElOb consists of sending the metadata MT which comprises either the encoded reduced mask obtained in step E8b, the pixel values ​​of which correspond to at least part of the coefficients MSr, or the set of values ​​taken by the segmented perceptual mask MPSd in each of the two-dimensional regions Zrd, including at least part of the coefficients MSr, as well as the plurality of lists of points Lrd. This step ElOb corresponds to step E3 of sending the data representative of the mask MS.

[0064] This second embodiment provides greater dynamics on the frequency of changes of the segmented perceptual masks and to further compress the segmented perceptual masks at the image packet level. Thus, in this second embodiment, the metadata throughput can be increased by a factor of 4 compared to the first embodiment.

[0065] Thus, the metadata MT accompanying the image packet S comprises either a set of encoded reduced masks corresponding to each image slice of the image packet S, or a set of pluralities of coefficients accompanied by partition descriptions in the form of lists of points, corresponding to each image slice of the image packet S.

[0066] Steps EOa to E6a and EOb to E8b or E8b' can be carried out indifferently on a reprogrammable computing machine (a PC computer, a DSP processor or a microcontroller) executing a program comprising a sequence of instructions, or on a dedicated computing machine (for example a set of logic gates such as an FPGA or an ASIC, or any other hardware module).

[0067] In the case where the processing means is produced with a reprogrammable computing machine, the corresponding program (i.e. the sequence of instructions) may be stored in a removable or non-removable storage medium, this storage medium being partially or totally readable by a computer or a processor.

[0068] A method for receiving data representative of a mask M of size MoxNo pixels for watermarking an image, by a receiving terminal, included in a video sequence received by this receiving terminal, is now described.

[0069] The receiving terminal receives the video sequence in image packets. Each image packet is divided into K successive image slices. The data representative of the mask M will be used for watermarking all the images in an image slice.

[0070] We consider a packet of images S of the video sequence received by the receiving terminal, and more particularly a slice of images T of this packet of images S. The method for receiving data representative of the mask M for watermarking the images of the slice of images T comprises, as illustrated in [Fig.6], the following steps: - a step E10 of receiving data representative of a segmented mask MS of size MxN pixels less than MoxNo pixels, where the representative data comprises a plurality of coefficients MSr, - a step E12 of reconstructing the mask M on the basis of the coefficients MSr, - a step E14 of obtaining a weighted mark MQP by applying the mask M to a mark MQ of size MoxNo, - a step El6 of watermarking each of the images in the image slice by applying the weighted mark MQP to each of these images.

[0071] In a first embodiment of the reception method according to the invention, the data representative of the segmented mask MS consist of an image Is of size MxN pixels smaller than MOxNO pixels. This image Is comprises a geometric distribution RG comprising R two-dimensional regions Zr. By geometric distribution, it is meant a partition of the image Is into R two-dimensional regions Zr. The pixels of each two-dimensional region Zr have as a value a corresponding coefficient MSr among the plurality of coefficients MSr.

[0072] The image Is corresponds for example to the reduced mask obtained in step E6a of the first embodiment of the method for sending data representative of a mask according to the invention previously described, for the image slice T. In this case, the image Is is representative of the activity of the reference image I of the image slice T.

[0073] Alternatively, the image Is corresponds to the reduced mask obtained in step E8b of the second embodiment of the method for sending data representative of a mask according to the invention previously described, for the image slice T.

[0074] In this first embodiment, the step E12 of reconstituting the mask M consists of an oversampling of the image Is to the resolution MoxNo pixels. The mask M is the image Is oversampled to the resolution MoxNo pixels.

[0075] It is considered here that a mark MQ is to be inserted into each of the images of the image slice T. The mark MQ is for example characteristic of the receiving terminal which decoded the video sequence and more particularly the image packet S.

[0076] Step E14 then consists of multiplying, pixel by pixel, the mark MQ by the mask M. The image MQP resulting from this multiplication is hereinafter called the weighted mark MQP. Thus, for each pixel, the value of the weighted mark MQP for this pixel is equal to the product of the value of the mask M for this pixel by the value of this pixel in the mask MQ.

[0077] In step E16, each image of the image slice T is watermarked by inserting the weighted mark MQP. In the case where the image Is corresponds either to the reduced mask obtained in step E6a of the first embodiment of the method for sending data representative of a mask according to the invention previously described, or to the reduced mask obtained in step E8b of the second embodiment of the method for sending data representative of a mask according to the invention previously described, the transparency of the weighted mark MQP is adapted to the statistical parameters of the reference image of the image slice, which contributes to the quality of the watermarking of the images of the image slice T.

[0078] In a second embodiment of the reception method according to the invention, the data representative of the segmented mask MS are made up of the plurality of coefficients MSr, and a plurality of R lists of points Lrd, each coefficient MSr being associated with a list of points Lrd. Each list of points Lrd defines the closed contour of a two-dimensional region Zrd of a matrix of size MxN pixels. The R two-dimensional regions Zrd form a partition of a matrix of size MxN pixels. The segmented mask MS is an image of size MxN pixels constructed as follows. The R two-dimensional regions Zrd are plotted from the plurality of R lists of points Lrd. The plotting can for example be carried out by means of an image calculation function applied to the R lists of points Lrd. Then, the coefficient MSr associated with the list of points Lrd is assigned to the pixels of the two-dimensional region Zrd.

[0079] The R lists of points Lrd may for example result from step E8b' of the second embodiment of the method for transmitting data representative of a mask according to the invention previously described.

[0080] In this second embodiment of the reception method according to the invention, steps E12, E14, and E16 take place as in the first embodiment of the reception method according to the invention.

[0081] The present invention is in no way limited to the embodiments described and shown, but those skilled in the art will be able to provide any variant in accordance with the invention.

[0082] In a variant, the geometric distribution RG can be defined not from a luminance component of the reference image I of a slice of images T but from the perceptual mask calculated on the basis of the reference image I. The geometric distribution RG is then coupled to the perceptual mask to obtain the segmented perceptual mask.

[0083] Furthermore, as indicated above, the various aspects of the invention also apply to the context of live television broadcast. In the television context, the metadata, i.e. the data representative of the masks corresponding to the different image slices of an image packet, are calculated in real time, and the transmission of the corresponding image packet is delayed by a gap of one or more image packets in order to allow the image data and the metadata which have just been calculated to be transmitted in the data stream.

[0084] Furthermore, the transmission method and the reception method according to the invention can be applied to a single image. In this case, the segmented perceptual mask is calculated on the basis of a perceptual mask calculated from statistical data of said image.

Claims

Claims

1. Method for transmitting data representative of a mask for watermarking an image included in a set comprising at least this image, the method comprising the following steps: - a step of defining (El) a geometric distribution, comprising R two-dimensional regions, by means of at least one segmentation of a luminance component constructed on the basis of at least one image of said set, - a step of assigning (E2) a coefficient to each two-dimensional region, - a step of sending (E3) data representative of the mask comprising at least part of the coefficients.

2. Transmission method according to claim 1, characterized in that the coefficient is determined as a function of statistical parameters of the image in the two-dimensional region.

3. Transmission method according to one of claims 1 or 2, characterized in that the coefficient is calculated as a function of coefficients contained in a perceptual mask and relating to the two-dimensional region.

4. Transmission method according to one of claims 2 or 3, characterized in that the statistical parameters of the image are determined on the basis of at least one image processing method chosen from a Laplace filter, a variance calculation, a Fourier transform calculation or a calculation of local binary patterns.

5. Transmission method according to one of claims 1 to 4, characterized in that the data representative of the mask sent in the sending step (E3) only comprise the coefficients respectively allocated to a fraction of the pixels of the mask during the allocation step (E2).

6. Transmission method according to one of claims 1 to 5, characterized in that: - the allocation step (E2) comprises the formation of a segmented mask in which each pixel has as its value the coefficient allocated to the two-dimensional region comprising said pixel, - the method comprises a step of sub-sampling said segmented mask into a sub-sampled segmented mask comprising at least part of the coefficients, - the representative data sent at the sending step (E3) correspond to the part.

7. Transmission method according to one of claims 1 to 4, characterized in that the data representative of the mask sent in the sending step (E3) comprise data defining at least part of said two-dimensional regions.

8. Transmission method according to one of claims 1 to 7, characterized in that the image belongs to a slice of images of a video packet.

9. Transmission method according to claim 8 characterized in that: - during the definition step (El), the at least one segmentation comprises P segmentations of P luminance components, each luminance component being constructed on the basis of one among P image sequences of the video packet, said P image sequences having a length less than or equal to the length of the image slice, - the definition step (El) further comprises the selection of a defined segmentation among the P segmentations, the R two-dimensional regions being derived from the defined segmentation, - during the allocation step (E2), the coefficient is equal to the average of the values ​​of the pixels of the two-dimensional region of a defined mask determined on the basis of the image sequence corresponding to the defined segmentation.

10. Transmission method according to claim 9, characterized in that, during the definition step (El), the segmentation defined among the P segmentations corresponds to a minimum error among P errors calculated, for each sequence of images, between a reference perceptual mask of the sequence of images and a segmented perceptual mask of the sequence of images.

11. Transmission method according to claim 10, characterized in that: - the pixels of a reference perceptual mask of a sequence of images have as their value the minimum value of the corresponding pixels of perceptual masks calculated on the basis of each of the images of the sequence of images, - each perceptual mask is calculated from statistical parameters of an image of the sequence of images, - for each segmented perceptual mask of a sequence of images, the pixels of each zone defined by the segmentation have as their value the average of the values ​​of the pixels of the reference perceptual mask in said area.

12. Transmission method according to claim 11, characterized in that the defined mask corresponds to the reference perceptual mask of the image sequence.

13. Method for receiving data representative of a mask for watermarking an image comprising the following steps: - a step of receiving data representative of a segmented mask, said representative data comprising a plurality of coefficients, - a step of reconstructing the mask on the basis of the coefficients, - a step of obtaining a weighted mark by applying the mask to a mark, - a step of watermarking the image by applying the weighted mark to the image.

14. Reception method according to claim 13, characterized in that the step of reconstructing the mask comprises the allocation of the coefficients to pixel zones comprising at least one pixel.

15. Reception method according to claim 13, characterized in that: - the data representative of the segmented mask further comprises data defining two-dimensional regions, - the step of reconstructing the mask comprises the tracing of the two-dimensional regions on the basis of the data defining the two-dimensional regions and the allocation of a coefficient to each of the two-dimensional regions.

16. Reception method according to claim 13 characterized in that: - the data representative of the segmented mask further comprises a plurality of lists of points defining the closed contours of two-dimensional regions, - the step of reconstructing the mask comprises the tracing of the two-dimensional regions by means of the plurality of lists of points and the allocation of a coefficient to each of the two-dimensional regions.

17. Reception method according to one of claims 13 to 16, characterized in that: - the image belongs to a slice of images of a video packet, - the mask is common to the images in the image slice.

Images