CN114626967A

CN114626967A - Digital watermark embedding and extracting method, device, equipment and storage medium

Info

Publication number: CN114626967A
Application number: CN202210267459.2A
Authority: CN
Inventors: 魏正佳; 刘兴
Original assignee: Sungrow Power Supply Co Ltd
Current assignee: Sungrow Power Supply Co Ltd
Priority date: 2022-03-17
Filing date: 2022-03-17
Publication date: 2022-06-14

Abstract

The invention discloses a digital watermark embedding and extracting method, a digital watermark embedding and extracting device, digital watermark embedding and extracting equipment and a storage medium. Obtaining an original image and a digital watermark image; at least one watermark embedding area of the original image is determined, so that the concealment of the digital watermark is improved; based on JPEG compression, a higher sampling rate is usually reserved for brightness components, and the self-adaptive brightness adjustment algorithm is used for sequentially and self-adaptively adjusting the brightness of pixel points of non-overlapping preset pixel areas in a watermark embedding area, so that a digital watermark image is embedded into the watermark embedding area to obtain the digital watermark embedded image, and the digital watermark embedded image has better robustness to combined attack of screenshot and JPEG compression storage.

Description

Digital watermark embedding and extracting method, device, equipment and storage medium

Technical Field

The present invention relates to the field of digital watermark technology, and in particular, to a digital watermark embedding and extracting method, apparatus, device, and storage medium.

Background

With the development of network and multimedia technologies, digital watermarking technology is widely applied to the protection of technical documents, PPT and PDF and other digital assets by enterprises as an important means for protecting digital copyright.

The existing digital watermarking method mainly aims at natural scene images, for document images such as posters, PPTs, technical documents and the like, the existing frequency domain watermarking algorithms such as Discrete Cosine Transform (DCT) and Singular Value Decomposition (SVD) are easily damaged by screenshot, and for the document images which are mostly mixed by characters and pictures and have a large number of blank regions and high-contrast regions with clear edges, the concealment is poor, and the information hiding amount is reduced; spatial watermarking algorithms such as Least Significant Bit (LSB) algorithms are easily damaged by JPEG compression storage.

Therefore, the application effect of the existing digital watermarking method in the document image is poor, and the joint attack of screenshot and JPEG compression storage is difficult to resist.

Disclosure of Invention

The invention provides a digital watermark embedding and extracting method, a device, equipment and a storage medium, which are used for solving the problems that the application effect of the existing digital watermark method in a document image is poor and the joint attack of screenshot and JPEG compression is difficult to resist, and have better robustness and high concealment to the screenshot and the JPEG compression.

According to an aspect of the present invention, there is provided a digital watermark embedding method, including:

acquiring an original image and a digital watermark image;

determining at least one watermark embedding area of the original image;

and carrying out self-adaptive adjustment on the brightness of pixel points of non-overlapping preset pixel areas in the watermark embedding area according to the digital watermark image so as to embed the digital watermark image into the watermark embedding area to obtain the digital watermark embedding image.

According to another aspect of the present invention, there is provided a digital watermark extraction method, including:

acquiring a brightness component image and a preset pixel size of a watermark image to be extracted, wherein the watermark image to be extracted is a digital watermark embedded image obtained by adopting a digital watermark embedding method; each pixel point of the brightness component image is the brightness component of each pixel point of the watermark image to be extracted in a YUV color mode; the preset pixel size is the pixel size of a preset pixel area;

performing image segmentation on the brightness component image based on a preset pixel size from the starting point position of the brightness component image to obtain a plurality of non-overlapping target pixel regions;

extracting watermark information of each target pixel region, wherein the watermark information is determined according to the brightness of pixel points in the target pixel region;

if the watermark information does not form a digital watermark image, the starting point position of the brightness component image is moved by taking a unit pixel as a step length in a target pixel area where the starting point position is located, the step of performing image segmentation on the brightness component image based on the pixel size of a preset pixel area to obtain a plurality of non-overlapping target pixel areas is returned, and the watermark information of each target pixel area is extracted until the digital watermark image or the starting point position is determined to finish traversing in the corresponding target pixel area.

According to another aspect of the present invention, there is provided a digital watermark embedding apparatus including:

the acquisition module is used for acquiring an original image and a digital watermark image;

a region determining module for determining at least one watermark embedding region of the original image;

and the watermark embedding module is used for carrying out self-adaptive adjustment on the pixel point brightness of the non-overlapping preset pixel areas in the watermark embedding area according to the digital watermark image so as to embed the digital watermark image into the watermark embedding area to obtain the digital watermark embedded image.

According to another aspect of the present invention, there is provided a digital watermark extraction apparatus including:

the system comprises an acquisition module, a storage module and a processing module, wherein the acquisition module is used for acquiring a brightness component image and a preset pixel size of a watermark image to be extracted, and the watermark image to be extracted is a digital watermark embedded image obtained by adopting a digital watermark embedding method; each pixel point of the brightness component image is the brightness component of each pixel point of the watermark image to be extracted in a YUV color mode; the preset pixel size is the pixel size of a preset pixel area;

the segmentation module is used for carrying out image segmentation on the brightness component image based on the size of a preset pixel from the starting point position of the brightness component image to obtain a plurality of non-overlapping target pixel areas;

the extraction module is used for extracting watermark information of each target pixel region, and the watermark information is determined according to the brightness of pixel points in the target pixel region;

and the determining module is used for moving the starting position of the brightness component image by taking a unit pixel as a step length in a target pixel area where the starting position is located if the watermark information does not form the digital watermark image, returning to execute the step of performing image segmentation on the brightness component image based on the pixel size of a preset pixel area to obtain a plurality of non-overlapping target pixel areas, and extracting the watermark information of each target pixel area until the digital watermark image or the starting position is determined to finish traversing in the corresponding target pixel area.

According to another aspect of the present invention, there is provided an electronic apparatus including:

at least one processor; and

a memory communicatively coupled to the at least one processor; wherein,

the memory stores a computer program executable by the at least one processor, the computer program being executable by the at least one processor to enable the at least one processor to perform the digital watermark embedding method and/or the digital watermark extraction method according to any of the embodiments of the present invention.

According to another aspect of the present invention, there is provided a computer-readable storage medium storing computer instructions for causing a processor to implement the digital watermark embedding method and/or the digital watermark extraction method according to any one of the embodiments of the present invention when the computer instructions are executed.

According to the technical scheme provided by the embodiment of the invention, the original image and the digital watermark image are obtained; at least one watermark embedding area of the original image is determined, so that the concealment of the digital watermark is improved; based on JPEG compression, a higher sampling rate is usually reserved for brightness components, and the self-adaptive brightness adjustment algorithm is used for sequentially and self-adaptively adjusting the brightness of pixel points in the non-overlapping preset pixel areas in the watermark embedding area, so that the digital watermark image is embedded into the watermark embedding area to obtain the digital watermark embedded image, and the joint attack of screenshot and JPEG compression storage has better robustness.

It should be understood that the statements in this section are not intended to identify key or critical features of the embodiments of the present invention, nor are they intended to limit the scope of the invention. Other features of the present invention will become apparent from the following description.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the description below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a flowchart of a digital watermark embedding method according to an embodiment of the present invention;

fig. 2 is a flowchart of a digital watermark embedding method according to a second embodiment of the present invention;

fig. 3 is a flowchart of a digital watermark embedding method according to a third embodiment of the present invention;

fig. 4 is a flowchart of a digital watermark extraction method according to a fourth embodiment of the present invention;

fig. 5 is a flowchart of a digital watermark extraction method according to a fifth embodiment of the present invention;

fig. 6 is a schematic structural diagram of a digital watermark embedding apparatus according to a sixth embodiment of the present invention;

fig. 7 is a schematic structural diagram of a digital watermark extraction apparatus according to a seventh embodiment of the present invention;

fig. 8 is a schematic structural diagram of an electronic device implementing the digital watermark embedding method or the digital watermark extraction method according to the embodiment of the present invention.

Detailed Description

In order to make those skilled in the art better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, shall fall within the protection scope of the present invention.

It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

Example one

Fig. 1 is a flowchart of a digital watermark embedding method according to an embodiment of the present invention, where the embodiment is applicable to embedding a watermark image in a natural scene image or a document image, and the method may be implemented by a digital watermark embedding apparatus, where the digital watermark embedding apparatus may be implemented in hardware and/or software, and the digital watermark embedding apparatus may be configured in an electronic device. As shown in fig. 1, the method includes:

and S110, acquiring an original image and a digital watermark image.

The original image is an image in which a digital watermark image needs to be embedded, and may be a natural scene image, or a document image such as a PPT, a poster, a technical document, and the like, where the document image means an image containing text information and non-text information. Compared with the natural scene image, the document image is characterized in that: the method has the characteristic of clear black and white, and the histogram discreteness of the document image is large; the low-brightness pixels in the document image are relatively few and are often distributed in the middle of the image.

The colors of each pixel point of the original image can adopt an RGB color mode or a YUV color mode. The principle of the RGB color scheme is to divide the color into three channels, red, green and blue, each channel being mixed in different proportions to describe a color. The YUV color mode describes a color with a luminance component and two chrominance components, Y representing luminance, U representing chrominance, and V representing the density of chrominance. The YUV color mode has the greatest characteristic that the brightness information and the color information are separated, and the gray scale change of a picture can be displayed according to the brightness information without the color information.

The digital watermark image refers to an image containing watermark information, the general digital watermark image needs to be preset according to user requirements, and the digital watermark image can be encrypted according to the user requirements. The structural form of the digital watermark image may be a two-dimensional code image or other preset images with symbolic significance, for example, characters, letters, and numbers with symbolic significance, which is not limited in this embodiment of the present invention. Generally, a digital watermark image adopts a binary sequence and can directly correspond to a (0,1) data bit stream, that is, the digital watermark image can be represented by a plurality of (0,1) bits of watermark information.

For example, the method for acquiring the digital watermark image may be to acquire the digital watermark image from a database, a cloud, or other storage devices, and the method for acquiring the original image may be to acquire the original image from the database, the cloud, or other storage devices, or to acquire the original image through an image acquisition device.

And S120, determining at least one watermark embedding area of the original image.

The watermark embedding area refers to an area in an original image where a watermark image is to be embedded, and the number of the watermark embedding areas may be one or more non-overlapping areas. Watermark information is embedded in a plurality of watermark embedding areas in the original image, so that a more stable watermark effect can be obtained.

It is easy to understand that the number of the horizontal pixel points and the vertical pixel points in the watermark embedding area should be larger than the maximum pixel of the structural form of the digital watermark image in the same direction, otherwise, the digital watermark image cannot be completely embedded into the watermark embedding area of the original image, so that complete watermark information cannot be extracted, or the digital watermark image exceeds the watermark embedding area, so that the watermark information cannot be concealed.

In a specific example, the method for determining the watermark embedding area of the original image may select a preset pixel size area with the largest average brightness value of each pixel point in the original image to be determined as the watermark embedding area, or may select a preset pixel size area with the largest average gray value of each pixel point in the original image to be determined as the watermark embedding area, so that a certain hiding effect may be achieved on watermark information.

It can be understood that the selection of the watermark embedding area is crucial to the hiding effect of the watermark information, and the appropriate watermark embedding area selection method can improve the hiding performance of digital watermark embedding. Therefore, the watermark embedding area can be scientifically selected based on the minimum perceptible distortion degree of each pixel point of the original image. The Just not possible Distortion (JND) is used to represent the maximum image Distortion that human eyes cannot perceive, and represents the tolerance of human eyes to image changes.

In another specific example, a Nonlinear Additive Masking Model (NAMM) is a computational Model that achieves minimal perceptible distortion, and the NAMM can be used to select a more covert watermark embedding region.

S130, carrying out self-adaptive adjustment on the brightness of pixel points of the non-overlapping preset pixel areas in the watermark embedding area according to the digital watermark image so as to embed the digital watermark image into the watermark embedding area to obtain the digital watermark embedding image.

The predetermined pixel area is an area with a predetermined pixel size, such as a rectangular area like a square matrix. Illustratively, the preset pixel size of the preset pixel region may be 3 × 5, 3 × 3, or 5 × 5. The watermark embedding area can be divided into a plurality of non-overlapping preset pixel areas according to the size of the preset pixel. In general, in order to easily determine the center point of the preset pixel region, a square matrix having an odd side length, such as a 3 × 3 or 5 × 5 square matrix, is selected. The location of the center point may be predetermined if the area is not a square matrix.

Specifically, target brightness values of pixel points in a preset pixel region corresponding to each bit of watermark information in the digital watermark image are sequentially determined, and the brightness values of the pixel points in the preset pixel region are adjusted to the target brightness values. The brightness change of each preset pixel region reflects the watermark information embedded in the watermark embedding region of the original image, the brightness of the pixel point is represented by a brightness component (Y component) in a YUV color mode, and is represented by a numerical value proportion of R, G, B in an RGB color mode, so that the digital watermark image is embedded in the watermark embedding region to obtain the digital watermark embedded image. The JPEG compression generally keeps a higher sampling rate on the brightness component, so that the digital watermark embedded image based on the digital watermark image embedded by the adaptive brightness adjustment algorithm has better robustness on the joint attack of screenshot and JPEG compression storage.

For example, the adaptive adjustment of the luminance of the pixel points in the non-overlapping preset pixel regions may be to adjust the luminance of each pixel point according to statistics such as an average value, a maximum value, or a minimum value of the luminance of each pixel point in the preset pixel region; or adjusting the brightness of each pixel point according to the minimum perceptible distortion degree corresponding to each pixel point in the preset pixel area; or a combination of the two.

In a specific embodiment, when the brightness of each pixel point in the preset pixel region is adjusted, different embedding step lengths may be used for the center pixel point and the non-center pixel point, and the embedding step length may be determined according to the minimum perceivable distortion and/or the average brightness of the pixel points corresponding to the pixel points in the preset pixel region.

According to the technical scheme provided by the embodiment of the invention, an original image and a digital watermark image are obtained; at least one watermark embedding area of the original image is determined, so that the concealment of the digital watermark is improved; based on JPEG compression, a higher sampling rate is usually reserved for brightness components, and the self-adaptive brightness adjustment algorithm is used for sequentially and self-adaptively adjusting the brightness of pixel points of non-overlapping preset pixel areas in a watermark embedding area, so that a digital watermark image is embedded into the watermark embedding area to obtain the digital watermark embedded image, and the digital watermark embedded image has better robustness to combined attack of screenshot and JPEG compression storage.

Optionally, the digital watermark image is an image subjected to encryption processing.

Specifically, the function of encrypting the digital watermark image is as follows: firstly, prevent that watermark information from revealing, secondly make a noise with the watermark image for the energy of image evenly distributed as far as possible mixes in the image noise better. The image encryption result requires a particular sensitivity to the initial value, and an incorrect initial value does not allow reading of the image.

The embodiment of the invention is not limited, and the common methods include Arnold transformation, Baker transformation, cat face transformation, chaotic sequence and the like. The pseudo-random sequence is generated by selecting Logistic mapping of the chaotic sequence method, the initial value sensitivity and the randomness are good, and the initial value can be used as a secret key.

Example two

Fig. 2 is a flowchart of a digital watermark embedding method according to a second embodiment of the present invention, which further details step S130 of the second embodiment. As shown in fig. 2, the method includes:

and S210, acquiring an original image and a digital watermark image.

And S220, determining at least one watermark embedding area of the original image.

S230, obtaining an original image brightness matrix corresponding to the watermark embedding area, wherein the original image brightness matrix comprises brightness components of all pixel points in the watermark embedding area of the original image in a YUV color mode.

The original image brightness matrix is a matrix formed by brightness components of all pixel points of a watermark embedding area corresponding to an original image in a YUV color mode.

Specifically, for an original image in a YUV color mode, the brightness of each pixel point in the watermark embedding area is extracted to obtain an original image brightness matrix. It should be noted that the image space standard often adopted in general life is an RGB color mode, and therefore, the luminance component of each pixel point in the watermark embedding region needs to be extracted after the original image is converted into the YUV color mode. The method for converting the original image from the RGB color mode to the YUV color mode may use any existing color mode conversion technology, and the embodiment of the present invention does not limit this.

And S240, dividing the original image brightness matrix into a plurality of non-overlapping preset pixel regions.

Specifically, the pixel size of the preset pixel region is set according to actual requirements, and generally, for convenience of calculation, the preset region may be set as a square matrix region with a side length of an odd number of pixels, for example, a 3 × 3 pixel square matrix region.

And dividing the original image brightness matrix into a plurality of non-overlapping preset square matrixes based on the preset pixel size.

For example, the original image luminance matrix may be divided into a plurality of non-overlapping predetermined pixel regions by dividing the original image luminance matrix into a plurality of non-overlapping predetermined pixel regions in units of a predetermined pixel size, and if the pixel size of the original image luminance matrix is w × h, the original image luminance matrix may be divided into m × n non-overlapping predetermined pixel regions of k × k, wherein,

it should be noted that, when dividing the pixel region, the image with edges less than the preset pixel width is negligible.

And S250, sequentially carrying out self-adaptive adjustment on the pixel point brightness of each preset pixel region in the original image brightness matrix according to the watermark information in the digital watermark image to obtain a target image brightness matrix.

The watermark information can be a data stream formed by watermark information of each bit in a word watermark image, when the self-adaptive brightness adjustment is carried out, the 1-bit watermark information is used for being embedded into a preset pixel region, and the brightness of pixel points of each preset pixel region is adjusted based on the watermark information of the digital watermark image.

Specifically, the brightness of the pixel points in each preset pixel region in the original image brightness matrix is adjusted through a self-adaptive adjustment algorithm to obtain a target image brightness matrix. The self-adaptive adjustment algorithm is that according to watermark information corresponding to the digital watermark image, self-adaptive brightness values of all pixel points in a preset pixel region corresponding to the watermark information are sequentially determined based on the self-adaptive brightness adjustment algorithm, and according to the self-adaptive brightness values, brightness of all pixel points in the preset pixel region in an original image brightness matrix is adjusted to obtain a target image brightness matrix.

The target image brightness matrix is used for reflecting the updated brightness of the watermark embedding area of the original image, the updated brightness can represent the embedded digital watermark image, and a higher sampling rate is usually reserved for brightness components based on JPEG compression, so that the target image brightness matrix has better robustness to combined attack of screenshot and JPEG compression storage.

And S260, synthesizing the brightness matrix of the target image and the chrominance component of the original image in the watermark embedding area to obtain the digital watermark embedding image.

The digital watermark embedded image refers to an original image embedded with a watermark image.

Specifically, the digital watermark embedded image can be obtained by synthesizing the luminance component (Y component) included in the target luminance matrix and the chrominance components (U and V components) of the original image in the watermark embedding area.

It should be noted that, if the original image is in the RGB color mode, the digital watermark embedded image in the YUV color mode can also be converted into the digital watermark embedded image in the RGB color mode.

According to the technical scheme of the embodiment of the invention, the original image brightness matrix corresponding to the watermark embedding area is extracted from the original image, the original image brightness matrix is divided into a plurality of non-overlapping preset pixel areas, the brightness of each preset pixel area in the original image brightness matrix is adjusted through a self-adaptive adjustment algorithm to obtain the target image brightness matrix, so that the target image brightness matrix and the chromaticity component of the original image in the watermark embedding area are synthesized to obtain the digital watermark embedding image, the digital watermark embedding image can be embedded into each data bit stream of the digital watermark image into the original image through the brightness component change of the original image, and a higher sampling rate is usually reserved for the brightness component based on JPEG compression, so that the method has better robustness for joint attack of screenshot and JPEG compression storage. Meanwhile, 1 bit of watermark information is embedded into a preset pixel region with a preset pixel size, and a digital watermark image can be extracted through limited traversal, so that the extraction process of the digital watermark image is simplified.

Optionally, according to the watermark information in the digital watermark image, performing adaptive adjustment on the pixel brightness of each preset pixel region in the original image brightness matrix in sequence to obtain a target image brightness matrix, including:

for each preset pixel region, acquiring an embedding step length corresponding to a central pixel point and a brightness average value of each non-central pixel point, wherein the embedding step length is the product of the minimum perceptible distortion degree corresponding to the central pixel point and an embedding intensity coefficient;

determining the central brightness value of the central pixel point according to the watermark information, the brightness average value and the embedding step length corresponding to the preset pixel area;

determining a brightness adjustment value of a non-central pixel point according to watermark information corresponding to a preset pixel area and an embedding step length;

and adjusting the brightness of the central pixel point of the preset pixel region to be a central brightness value, and adjusting the brightness of the non-central pixel point of the preset pixel region based on the brightness adjustment value to obtain a target image brightness matrix.

Each preset pixel region may include a center pixel point and a non-center pixel point. For example, for a 3 × 3 predetermined pixel area, the pixel matrix is [0,1,2,3,4,5,6,7,8], the center pixel is the 4 th pixel, and the rest pixels are non-center pixels.

Specifically, for each preset pixel region, a central brightness value of a central pixel point and a brightness adjustment value of a non-central pixel point are respectively determined, on the basis of an original image brightness matrix, the brightness of the central pixel point of the preset pixel region is adjusted to be the central brightness value, and the brightness of all non-central pixel points in the preset pixel region is adjusted based on the brightness adjustment value, so that a target image brightness matrix can be obtained.

In a specific embodiment, the manner of determining the central brightness value may be determined according to the watermark information (i.e. 0 or 1) embedded into the preset pixel region, an embedding step corresponding to the central pixel point in the preset pixel region, and a brightness average value of each non-central pixel point. The brightness adjustment value may be determined according to an embedding step corresponding to a central pixel point in the preset pixel region.

Wherein the average brightness value of each non-central pixel point is

avgY is the average brightness value of non-central pixel points in a preset pixel area, and Y (i, j) is the brightness of pixel points in the ith row and j column; k is the number of pixels of the preset pixel area with side length.

Wherein the embedding step corresponding to the central pixel point is the product of the minimum perceptible distortion and the embedding intensity coefficient corresponding to the central pixel point, i.e.

λ＝α×JND；

Lambda is the embedding step length corresponding to the central pixel point, JND is the minimum perceptible distortion corresponding to the central pixel point, and alpha is the embedding intensity coefficient. The embedding strength coefficient can be set according to actual requirements. The embedding step length lambda influences the concealment and the robustness of the digital watermark image, and the larger the lambda is, the better the robustness is and the worse the concealment is.

The embedding step length is determined according to the minimum perceptible distortion corresponding to the central pixel point in the preset pixel region, the central brightness value of the central pixel point is determined according to the watermark information corresponding to the preset pixel region, the embedding step length and the brightness average value of each non-central pixel point, the brightness adjusting value of the non-central pixel point is determined according to the watermark information corresponding to the preset pixel region and the embedding step length, the self-adaptive adjustment of each pixel point in the preset pixel region can be achieved by synthesizing the sensitivity of human eyes to the brightness, and the concealment and the robustness of the digital watermark image are guaranteed.

Optionally, determining a central brightness value of the central pixel point according to the watermark information, the brightness average value, and the embedding step length corresponding to the preset pixel region, includes:

if the watermark information corresponding to the preset pixel region is first watermark information, determining the central brightness value of the central pixel point as the sum of the brightness average value and the embedding step length;

and if the watermark information corresponding to the preset pixel region is the second watermark information, determining the central brightness value of the central pixel point as the difference between the brightness average value and the embedding step length.

The first watermark information and the second watermark information are respectively one bit of watermark information in the watermark information represented by binary data, for example, if the first watermark information is watermark information 0, the second watermark information is watermark information 1, or if the first watermark information is watermark information 1, the second watermark information is watermark information 0.

Therefore, according to the watermark information in the digital watermark image, the specific implementation algorithm for sequentially and adaptively adjusting the pixel point brightness of each preset pixel area in the original image brightness matrix is as follows:

wherein,

the center point of the b-th preset pixel area in the watermark embedding area is. W_bIs the watermark information of the b-th bit of the digital watermark image, and the value range of b is the water in the digital watermark imageThe number of bits of the printed information.

According to the watermark information corresponding to the preset pixel region, the central brightness value of the central pixel point is determined as the sum of the brightness average value and the embedding step length or the difference between the brightness average value and the embedding step length, so that the watermark information embedded into the preset pixel region is reflected according to the size relation between the embedding step length of the central pixel point and the brightness average value, the embedding step length of the central pixel point is determined by synthesizing the sensitivity of human eyes to the brightness, and the extraction of the digital watermark image is facilitated while the concealment of the digital watermark image is ensured.

Optionally, determining a brightness adjustment value of the non-center pixel point according to the watermark information and the embedding step corresponding to the preset pixel region, includes:

acquiring the number of non-central pixel points in a preset pixel region;

if the watermark information corresponding to the preset pixel region is second watermark information, determining the brightness adjustment value of the non-central pixel point as the ratio of the embedding step length to the number of the non-central pixel points;

and if the watermark information corresponding to the preset pixel region is the first watermark information, determining the brightness adjustment value of the non-central pixel point as the opposite number of the ratio.

Specifically, the number of non-central pixel points in a preset pixel region is k multiplied by k-1; if the watermark information corresponding to the preset pixel region is the second watermark information, the brightness adjustment value of the non-central pixel point is determined as the ratio of the embedding step length to the number of the non-central pixel points, namely, the brightness adjustment value B₂Increasing the brightness of the non-central pixel point in the preset pixel area by a brightness adjustment value; if the watermark information corresponding to the preset pixel region is the first watermark information, the brightness adjustment value of the non-central pixel point is determined as the opposite number of the ratio of the embedding step length to the number of the non-central pixel points, namely, the brightness adjustment value B₂λ/(k × k-1), that is, the brightness of the non-central pixel in the predetermined pixel region is decreased by the brightness adjustment value.

And taking the ratio of the embedding step length to the number of the non-central pixel points as a brightness adjustment value of the non-central pixel points in the preset pixel region, wherein the brightness adjustment value is used for adjusting the brightness of the non-central pixel points in the preset pixel region, so that the overall brightness of each pixel region in the watermark embedding region is not changed, and information can be embedded in the region with the brightness of 0 or 255.

EXAMPLE III

Fig. 3 is a flowchart of a digital watermark embedding method according to a third embodiment of the present invention, and this embodiment further refines step S120 or S220 in the foregoing embodiment. As shown in fig. 3, the method includes:

and S310, acquiring an original image and a digital watermark image.

And S320, determining the gray level image of the original image.

Under the RGB color mode, each pixel point of the gray image is the same according to the color values of the red channel, the green channel and the blue channel, and different gray levels are expressed according to the size of the color values. In the YUV color mode, the color of each pixel of the grayscale image is represented by a luminance component (Y component).

In a specific example, for an original image in the RGB color mode, an average value of color values of three channels of red, green and blue is used as a gray value of the gray image.

In another specific example, for an original image in YUV color mode, a gray image is obtained by extracting the luminance component of the delayed image.

And S330, determining a minimum perceptible distortion matrix of the gray-scale image through a nonlinear addition masking model, and mapping the minimum perceptible distortion matrix to the gray-scale image to obtain a mapped image.

Among them, a Nonlinear Additive Masking Model (NAMM) is a computational Model for achieving the minimum perceptible distortion. The NAMM model belongs to a spatial domain pixel domain model, takes the overlapping effect of brightness self-adaptive masking and contrast masking into account, can more intuitively provide a human eye minimum perceivable (JND) threshold value on a pixel domain, and is used for evaluating the influence degree of human vision at different image positions.

Specifically, a minimum perceptible distortion matrix formed by the minimum perceptible distortion of each pixel point in the gray-scale image can be determined through the NAMM, the minimum perceptible distortion matrix is mapped onto the gray-scale image to obtain a mapped image, the gray-scale value of each pixel point in the mapped image is the minimum perceptible distortion corresponding to the pixel point, and the mapped image reflects the minimum perceptible distortion corresponding to each pixel point in the original image. The higher the minimum perceptible distortion value, the higher the threshold at which the distortion of the pixel can be perceived by the human eye.

An exemplary, non-linear additive masking model (NAMM), is formed by the nonlinear superposition of background luminance adaptation and contrast masking, i.e.

JND(x,y)＝T_b(x,y)+T_c(x,y)+C_l×min{T_b(x,y),T_c(x,y)}；

Wherein, T_b(x, y) denotes the background luminance adaptive perceptibility threshold, T_c(x, y) denotes the contrast-masking perceptible threshold, C_lRepresenting the overlap effect of the two in the luminance component, C can be taken_l＝0.3。

T_b(x, y) is represented as:

wherein, I_Y(x, y) is the average background luminance of the pixel whose coordinates are located at (x, y). The calculation method is as follows:

wherein, the B matrix operator is:

T_c(x, y) is represented as:

T_c(x,y)＝γ_luma×G(x,y)；

wherein, γ_lumaIs a control parameter of the luminance component, gamma_luma0.117. G (x, y) is the maximum value of the gradient in 4 directions (0 °, 45 °, 90 °, and 135 °) of the pixel having coordinates (x, y).

And S340, traversing the mapping image according to a preset sliding template to obtain each alternative area, wherein the size of the preset sliding template is determined by the pixel sizes of the digital watermark image and the preset pixel area.

The size of the alternative area is at least the product of the pixel sizes of the digital watermark image and the preset pixel area, so that the size of the preset sliding template is determined by the pixel sizes of the digital watermark image and the preset pixel area.

A plurality of candidate areas with the same size as the preset sliding template can be obtained by traversing the mapping image through the preset sliding template, and a proper watermark embedding area can be selected from the candidate areas.

And S350, determining the candidate area meeting the preset condition as a watermark embedding area.

Specifically, the preset condition may be that an average value of the minimum perceivable distortion degrees of the candidate regions is maximum, the average value of the minimum perceivable distortion degrees is greater than a preset threshold, or a ratio of the minimum perceivable distortion degrees to the preset threshold is maximum.

The preset number of the watermark embedding areas can be one or more, and can be set according to actual conditions.

Optionally, if the number of the candidate regions that satisfy the preset condition is multiple, each of the candidate regions that satisfy the preset condition and are not overlapped with each other is determined as the watermark embedding region.

Specifically, if a plurality of watermark embedding areas are determined, it is necessary to ensure that the plurality of watermark embedding areas do not overlap with each other, so as to ensure that the digital watermark images embedded in the plurality of watermark embedding areas are not covered.

And S360, carrying out self-adaptive adjustment on the brightness of pixel points of the non-overlapping preset pixel areas in the watermark embedding area according to the digital watermark image so as to embed the digital watermark image into the watermark embedding area to obtain the digital watermark embedding image.

According to the technical scheme of the embodiment of the invention, a minimum perceptible distortion matrix of a gray image is determined through a nonlinear addition masking model, and the minimum perceptible distortion matrix is mapped to the gray image to obtain a mapped image; according to the method, the candidate areas are obtained by traversing the mapping image according to the preset sliding template, the average gray value of each pixel point in each candidate area is determined, at least one candidate area with the maximum average gray value is determined as a watermark embedding area, and the optimal watermark embedding area can be determined according to the pixel distortion threshold value which can be perceived by human eyes, so that the concealment of the digital watermark image is improved, and the embedding of the digital watermark is not easily perceived by people.

Optionally, determining a minimum perceivable distortion matrix of the grayscale image through a non-linear addition masking model, including:

extracting the resolution of the gray level image based on a preset extraction frequency to obtain a target gray level image;

determining a nonlinear addition masking model coefficient matrix of the target gray level image through a nonlinear addition masking model;

and carrying out interpolation processing on the nonlinear addition masking model coefficient matrix based on a preset interpolation frequency to obtain a minimum perceptible distortion matrix of the gray-scale image, wherein the preset extraction frequency and the preset interpolation frequency are reciprocal.

Specifically, the method of directly determining the nonlinear addition masking model coefficient matrix of the gray-scale image as the minimum perceptible distortion matrix by using the nonlinear addition masking model requires a large amount of calculation, consumes a large amount of hardware resources, and has low calculation efficiency so that the determination time of the watermark embedding area is long. Therefore, the resolution of the gray image is firstly extracted based on the preset extraction frequency to obtain the target gray image, the resolution of the target gray image is reduced, and then the nonlinear addition masking model is used for calculation, so that the calculation amount can be reduced, and the calculation efficiency is improved. By reducing the resolution of the gray-scale image to 1/3 and then performing the NAMM model coefficient calculation, the calculation time can be shortened to 1/8.

After the NAMM model operation, interpolation processing is carried out on the nonlinear addition masking model coefficient matrix based on the preset interpolation frequency to obtain the minimum perceptible distortion matrix of the gray-scale image, the preset extraction frequency and the preset interpolation frequency are reciprocal, so that the minimum perceptible distortion matrix can be restored to the size of the gray-scale image, and the minimum perceptible distortion matrix can be conveniently mapped to the gray-scale image one by one.

Example four

Fig. 4 is a flowchart of a digital watermark extraction method according to a fourth embodiment of the present invention, where this embodiment is applicable to a case where digital watermark extraction is performed on a digital watermark embedded image obtained by using the digital watermark embedding method according to the fourth embodiment of the present invention, and the method may be executed by a digital watermark extraction device, where the digital watermark extraction device may be implemented in a form of hardware and/or software, and the digital watermark embedding extraction device may be configured in an electronic device. As shown in fig. 4, the method includes:

s410, acquiring a brightness component image and a preset pixel size of a watermark image to be extracted, wherein the watermark image to be extracted is a digital watermark embedded image obtained by adopting the digital watermark embedding method of any one of the first to third embodiments; each pixel point of the brightness component image is the brightness component of each pixel point of the watermark image to be extracted in the YUV color mode; the predetermined pixel size is the pixel size of the predetermined pixel region in any one of the first to third embodiments.

The watermark image to be extracted is a digital watermark embedded image obtained by the digital watermark embedding method of any one of the first to third embodiments.

It should be noted that the digital watermark extraction process is the inverse process of the digital watermark embedding process, and only the digital watermark extraction method matched with the digital watermark embedding method is adopted to extract the watermark of the digital watermark embedded image, and the digital watermark embedded image obtained by other digital watermark embedding methods cannot be successfully extracted to obtain the correct watermark image. Therefore, when extracting the watermark from the watermark image to be extracted, it is necessary to obtain the preset parameters used in the digital watermark extraction method, such as the pixel size of the preset pixel region, and to implement the inverse process of digital watermark embedding.

Specifically, a brightness component image of the watermark image to be extracted is obtained, and each pixel point of the brightness component image is a brightness component of each pixel point of the watermark image to be extracted in a YUV color mode. If the watermark image to be extracted adopts an RGB color mode, the watermark image to be extracted in the RGB color mode needs to be converted into the watermark image to be extracted in the YUV color mode, and then the brightness component is extracted to obtain the brightness component image of the watermark image to be extracted. The method for converting the original image from the RGB color mode to the YUV color mode may use any existing color mode conversion technology, which is not limited in the embodiment of the present invention.

And S420, carrying out image segmentation on the brightness component image based on the preset pixel size from the starting point position of the brightness component image to obtain a plurality of non-overlapping target pixel regions.

The starting point position of the luminance component image may be set according to actual requirements, and generally, the position of the (0,0) th pixel point of the luminance component image, that is, the position of the (0,0) th pixel point of the watermark image to be extracted may be selected as the starting point position, and of course, the position of the last pixel point or the positions of other pixel points may also be used as the starting point position.

Specifically, starting from the starting position, the luminance component image is subjected to image segmentation based on a preset pixel size to obtain a plurality of target pixel regions which are not overlapped with each other. It can be understood that the target pixel area is exactly the same as the preset pixel area divided by the luminance matrix of the original image in the digital watermark embedding process.

For example, if the pixel size of the luminance component image is w × h and the predetermined pixel size is k × k, the luminance component image may be divided into m × n target pixel regions where the predetermined pixels are k × k and do not overlap with each other, wherein,

it should be noted that, when dividing the target pixel region, the image with the edge less than the preset pixel width is negligible.

S430, extracting watermark information of each target pixel region, wherein the watermark information is determined according to the brightness of pixel points in the target pixel region.

Specifically, the watermark information in each target pixel region is extracted, and because the embedded watermark information is represented by the brightness of each pixel point in the preset pixel region when the digital watermark image is embedded, the watermark information can be determined according to the brightness of the pixel point in the target pixel region.

S440, if the watermark information does not form the digital watermark image, the starting point position of the brightness component image is moved by taking the unit pixel as the step length in the target pixel area where the starting point position is located, and the step of performing image segmentation on the brightness component image based on the pixel size of the preset pixel area to obtain a plurality of non-overlapping target pixel areas is returned until the digital watermark image or the starting point position is determined to complete traversal in the corresponding target pixel area.

Specifically, when a digital watermark image is embedded, only the digital watermark image is embedded in the watermark embedding area, and a target pixel area obtained by dividing the luminance component image from the starting point position of the watermark image to be extracted may have a deviation from each preset pixel area in the watermark embedding area in the digital watermark image embedding process, and the digital watermark image cannot be formed if the watermark information is determined according to the luminance of the pixel points in the target pixel area.

The digital watermark extraction method does not require the alignment of the starting points, but moves the starting point position of the brightness component image by taking a unit pixel as a step length in the target pixel area where the starting point position is located. And at each time of moving the starting point position, based on the moved starting point position, returning to execute the steps of carrying out image segmentation on the brightness component image based on the pixel size of the preset pixel area to obtain a plurality of non-overlapping target pixel areas, and extracting the watermark information of each target pixel area. When the starting point position completes traversing or determining the digital watermark image in the corresponding target pixel region, all the digital watermark images embedded in the watermark image to be extracted can be extracted.

It should be noted that if one or a known number of digital watermark images exist in the watermark images to be extracted, it is determined that traversal operation does not need to be continuously performed after all correct digital watermark images are extracted; if the watermark image to be extracted includes a plurality of digital watermark images of unknown quantity, all the digital watermark images embedded in the watermark image to be extracted can be determined to be extracted only when the traversal is completed in the corresponding target pixel region at the starting position.

Therefore, the watermark image can be extracted blindly through searching for the pixels contained in the maximum target pixel area for several times, and the watermark image has the capability of resisting shearing with any width.

According to the technical scheme of the embodiment of the invention, a brightness component image and a preset pixel size of a watermark image to be extracted are obtained, the brightness component image is subjected to image segmentation based on the preset pixel size from the starting position of the brightness component image to obtain a plurality of non-overlapping target pixel areas, watermark information of each target pixel area is extracted, and the watermark information is determined according to the pixel point brightness in the target pixel area; if the watermark information does not form a digital watermark image, the starting point position of the brightness component image is moved by taking a unit pixel as a step length in a target pixel area where the starting point position is located, the step of performing image segmentation on the brightness component image based on the pixel size of a preset pixel area to obtain a plurality of non-overlapping target pixel areas is returned, and the watermark information of each target pixel area is extracted until the digital watermark image or the starting point position is determined to finish traversal in the corresponding target pixel area, the starting point alignment is not required, and the watermark image can be extracted blindly through a plurality of searches of pixels contained in the maximum target pixel area, so that the watermark image has the capability of resisting the shearing of any width.

Optionally, after the digital watermark image is determined, the method further comprises

Acquiring a key of a digital watermark image embedded in a watermark image to be extracted;

decrypting the digital watermark image based on the key;

and carrying out information identification on the decrypted digital watermark image.

Specifically, if the digital watermark image embedded in the digital watermark embedding process is an encrypted image, the digital watermark image directly extracted from the watermark image to be extracted is also an encrypted image, and a key of the digital watermark image embedded in the watermark image to be extracted needs to be acquired, the digital watermark image is decrypted based on the key, and the decrypted digital watermark image is subjected to information identification, so that the relevant information loaded in the digital watermark image can be obtained.

EXAMPLE five

Fig. 5 is a flowchart of a digital watermark embedding method according to a fifth embodiment of the present invention, and this embodiment further details step S420 of the foregoing embodiment. As shown in fig. 5, the method includes:

s510, acquiring a brightness component image and a preset pixel size of a watermark image to be extracted, wherein the watermark image to be extracted is a digital watermark embedded image obtained by adopting the digital watermark embedding method of any one of the first to third embodiments; each pixel point of the brightness component image is the brightness component of each pixel point of the watermark image to be extracted in the YUV color mode; the predetermined pixel size is the pixel size of the predetermined pixel region in any one of the first to third embodiments.

S520, carrying out image segmentation on the brightness component image based on the preset pixel size from the starting point position of the brightness component image to obtain a plurality of target pixel regions which are not overlapped with each other.

S530, for each target pixel area, extracting the brightness of each pixel point in the target pixel area.

Specifically, for each segmented target pixel region, the brightness of each pixel point of the brightness component image in the target pixel region is extracted.

And S540, determining watermark information of the target pixel area according to the brightness of each pixel point.

Specifically, the watermark information embedded in each target pixel region is determined based on the brightness change rule of each pixel point in the target pixel region when the digital watermark image is embedded in the original image.

For example, the embedded watermark information in the digital watermark image embedding method is 0 or 1, and the method for determining the watermark information of the target pixel region according to the brightness of each pixel point may be to determine the watermark information according to the brightness of a central pixel point and the average brightness of non-central pixel points in the target pixel region.

And S550, if the watermark information does not form the digital watermark image, moving the starting position of the luminance component image in the target pixel region where the starting position is located by taking the unit pixel as the step length, and returning to execute the step of performing image segmentation on the luminance component image based on the pixel size of the preset pixel region to obtain a plurality of non-overlapping target pixel regions until the digital watermark image or the starting position is determined to finish traversing in the corresponding target pixel region.

Acquiring a brightness component image and a preset pixel size of a watermark image to be extracted, wherein the watermark image to be extracted is a digital watermark embedded image obtained by adopting the digital watermark embedding method in any one of the first to third embodiments; each pixel point of the brightness component image is the brightness component of each pixel point of the watermark image to be extracted in the YUV color mode; the preset pixel size is the pixel size of the preset pixel region in any one of the first to third embodiments; performing image segmentation on the brightness component image based on the size of a preset pixel from the starting point position of the brightness component image to obtain a plurality of non-overlapping target pixel regions; for each target pixel area, extracting the brightness of each pixel point in the target pixel area; if the watermark information does not form a digital watermark image, moving the starting position of the brightness component image by taking a unit pixel as a step length in a target pixel area where the starting position is located, returning to execute the step of performing image segmentation on the brightness component image based on the pixel size of a preset pixel area to obtain a plurality of non-overlapping target pixel areas until the digital watermark image or the starting position is determined to finish traversing in the corresponding target pixel area; the watermark image can be extracted blindly through searching for a plurality of times by the pixels contained in the maximum target pixel area without requiring alignment of the starting points, and the watermark image has the capability of resisting shearing with any width. Meanwhile, the embedded watermark information can be determined by removing the brightness of each pixel point in the target pixel, and the extraction method is simple, fast and easy to implement.

Optionally, determining watermark information of the target pixel region according to the brightness of each pixel point includes:

determining the average brightness of each non-central pixel point in the target pixel region;

if the brightness of the central pixel point is larger than the average brightness, determining that the watermark information embedded in the target pixel area is first watermark information;

and if the brightness of the central pixel point is less than or equal to the average brightness, determining that the watermark information embedded in the target pixel area is the second watermark information.

Specifically, the average brightness of each non-central pixel point in the pixel region of the target region is calculated. And comparing the size relationship between the central pixel point and the average brightness. According to the strategy of embedding the digital watermark image into the original image, if the brightness of the central pixel point is greater than the average brightness, determining that the watermark information embedded in the target pixel area is first watermark information; and if the brightness of the central pixel point is less than or equal to the average brightness, determining that the watermark information embedded in the target pixel area is the second watermark information.

EXAMPLE six

Fig. 6 is a schematic structural diagram of a digital watermark embedding apparatus according to a sixth embodiment of the present invention. As shown in fig. 6, the apparatus includes: an acquisition module 610, a region determination module 620 and a watermark embedding module 630.

The acquiring module 610 is configured to acquire an original image and a digital watermark image;

a region determining module 620, configured to determine at least one watermark embedding region of the original image;

the watermark embedding module 630 is configured to perform adaptive adjustment on pixel brightness of each non-overlapping preset pixel region in the watermark embedding region according to the digital watermark image, so that the digital watermark image is embedded into the watermark embedding region to obtain a digital watermark embedded image.

Optionally, the watermark embedding module 630 includes:

the brightness matrix obtaining unit is used for obtaining an original image brightness matrix corresponding to the watermark embedding area, and the original image brightness matrix is formed by brightness components of all pixel points in the watermark embedding area of the original image in a YUV color mode;

the area dividing unit is used for dividing the original image brightness matrix into a plurality of non-overlapping preset pixel areas;

the self-adaptive adjusting unit is used for sequentially carrying out self-adaptive adjustment on the pixel point brightness of each preset pixel region in the original image brightness matrix according to the watermark information in the digital watermark image to obtain a target image brightness matrix;

and the synthesizing unit is used for synthesizing the target image brightness matrix and the chrominance components of the original image in the watermark embedding area to obtain a digital watermark embedding image.

Optionally, the adaptive adjusting unit includes:

the acquisition subunit is used for acquiring an embedding step length corresponding to the central pixel point and a brightness average value of each non-central pixel point for each preset pixel region, wherein the embedding step length is the product of the minimum perceptible distortion degree corresponding to the central pixel point and an embedding intensity coefficient;

the first determining subunit is configured to determine a central brightness value of a central pixel point according to the watermark information corresponding to the preset pixel region, the brightness average value, and the embedding step length;

the second determining subunit is configured to determine a brightness adjustment value of the non-center pixel according to the watermark information corresponding to the preset pixel region and the embedding step length;

and the brightness adjusting subunit is used for adjusting the brightness of the central pixel point of the preset pixel area to the central brightness value, and adjusting the brightness of the non-central pixel point of the preset pixel area based on the brightness adjusting value to obtain a target image brightness matrix.

Optionally, the first determining subunit is specifically configured to:

and if the watermark information corresponding to the preset pixel region is second watermark information, determining the central brightness value of the central pixel point as the difference between the brightness average value and the embedding step length.

Optionally, the second determining subunit is specifically configured to:

acquiring the number of non-central pixel points in the preset pixel area;

and if the watermark information corresponding to the preset pixel region is first watermark information, determining the brightness adjustment value of the non-central pixel point as the opposite number of the ratio.

Optionally, the region determining module 620 includes:

a gradation determining unit for determining a gradation image of the original image;

the matrix determining unit is used for determining a minimum perceptible distortion matrix of the gray-scale image through a nonlinear addition masking model, and mapping the minimum perceptible distortion matrix to the gray-scale image to obtain a mapping image;

the traversing unit is used for traversing the mapping image according to a preset sliding template to obtain each alternative area, and the size of the preset sliding template is determined by the pixel sizes of the digital watermark image and the preset pixel area;

and an embedded area determining unit which determines the candidate area satisfying the preset condition as the watermark embedding area.

Optionally, the matrix determining unit is specifically configured to:

The digital watermark embedding device provided by the embodiment of the invention can execute the digital watermark embedding method provided by any embodiment of the invention, and has corresponding functional modules and beneficial effects of the execution method.

EXAMPLE seven

Fig. 7 is a schematic structural diagram of a digital watermark extraction apparatus according to a seventh embodiment of the present invention. As shown in fig. 7, the apparatus includes: an acquisition module 710, a segmentation module 720, an extraction module 730, and a determination module 740.

The acquiring module 710 is configured to acquire a luminance component image and a preset pixel size of a watermark image to be extracted, where the watermark image to be extracted is a digital watermark embedded image obtained by using the digital watermark embedding method according to any embodiment; each pixel point of the brightness component image is the brightness component of each pixel point of the watermark image to be extracted in a YUV color mode; the preset pixel size is the pixel size of the preset pixel region in any embodiment;

a segmentation module 720, configured to perform image segmentation on the luminance component image based on a preset pixel size from a starting position of the luminance component image to obtain a plurality of non-overlapping target pixel regions;

an extracting module 730, configured to extract watermark information of each target pixel region, where the watermark information is determined according to brightness of a pixel point in the target pixel region;

a determining module 740, configured to, if the watermark information does not form a digital watermark image, move the starting point position of the luminance component image in the target pixel region where the starting point position is located by using a unit pixel as a step length, return to the step of performing image segmentation on the luminance component image based on the pixel size of a preset pixel region to obtain a plurality of non-overlapping target pixel regions, and extract watermark information of each target pixel region until it is determined that the digital watermark image or the starting point position completes traversal in the corresponding target pixel region.

Optionally, the extracting module 730 includes:

the extraction unit is used for extracting the brightness of each pixel point in each target pixel area;

and the determining unit is used for determining the watermark information of the target pixel area according to the brightness of each pixel point.

Optionally, the determining unit is specifically configured to:

and if the brightness of the central pixel point is less than or equal to the average brightness, determining that the watermark information embedded in the target pixel area is second watermark information.

Optionally, also include

The key acquisition module is used for acquiring a key of the digital watermark image embedded in the watermark image to be extracted;

the decryption module is used for decrypting the digital watermark image based on the secret key;

and the identification module identifies the information of the decrypted digital watermark image.

Example eight

FIG. 8 illustrates a schematic diagram of an electronic device 10 that may be used to implement an embodiment of the invention. Electronic devices are intended to represent various forms of digital computers, such as laptops, desktops, workstations, personal digital assistants, servers, blade servers, mainframes, and other appropriate computers. The electronic device may also represent various forms of mobile devices, such as personal digital assistants, cellular phones, smart phones, wearable devices (e.g., helmets, glasses, watches, etc.), and other similar computing devices. The components shown herein, their connections and relationships, and their functions, are meant to be exemplary only, and are not meant to limit implementations of the inventions described and/or claimed herein.

As shown in fig. 8, the electronic device 10 includes at least one processor 11, and a memory communicatively connected to the at least one processor 11, such as a Read Only Memory (ROM)12, a Random Access Memory (RAM)13, and the like, wherein the memory stores a computer program executable by the at least one processor, and the processor 11 can perform various suitable actions and processes according to the computer program stored in the Read Only Memory (ROM)12 or the computer program loaded from a storage unit 18 into the Random Access Memory (RAM) 13. In the RAM 13, various programs and data necessary for the operation of the electronic apparatus 10 can also be stored. The processor 11, the ROM 12, and the RAM 13 are connected to each other via a bus 14. An input/output (I/O) interface 15 is also connected to bus 14.

A number of components in the electronic device 10 are connected to the I/O interface 15, including: an input unit 16 such as a keyboard, a mouse, or the like; an output unit 17 such as various types of displays, speakers, and the like; a storage unit 18 such as a magnetic disk, an optical disk, or the like; and a communication unit 19 such as a network card, modem, wireless communication transceiver, etc. The communication unit 19 allows the electronic device 10 to exchange information/data with other devices via a computer network, such as the internet, and/or various telecommunication networks.

The processor 11 may be a variety of general and/or special purpose processing components having processing and computing capabilities. Some examples of processor 11 include, but are not limited to, a Central Processing Unit (CPU), a Graphics Processing Unit (GPU), various specialized Artificial Intelligence (AI) computing chips, various processors running machine learning model algorithms, a Digital Signal Processor (DSP), and any suitable processor, controller, microcontroller, or the like. The processor 11 performs the various methods and processes described above, such as a digital watermark embedding method or a digital watermark extraction method.

In some embodiments, the digital watermark embedding method or the digital watermark extraction method may be implemented as a computer program tangibly embodied in a computer-readable storage medium, such as storage unit 18. In some embodiments, part or all of the computer program may be loaded and/or installed onto the electronic device 10 via the ROM 12 and/or the communication unit 19. When the computer program is loaded into the RAM 13 and executed by the processor 11, one or more steps of the digital watermark embedding method or the digital watermark extraction method described above may be performed. Alternatively, in other embodiments, the processor 11 may be configured to perform the digital watermark embedding method or the digital watermark extraction method by any other suitable means (e.g., by means of firmware).

Various implementations of the systems and techniques described here above may be implemented in digital electronic circuitry, integrated circuitry, Field Programmable Gate Arrays (FPGAs), Application Specific Integrated Circuits (ASICs), Application Specific Standard Products (ASSPs), system on a chip (SOCs), load programmable logic devices (CPLDs), computer hardware, firmware, software, and/or combinations thereof. These various embodiments may include: implemented in one or more computer programs that are executable and/or interpretable on a programmable system including at least one programmable processor, which may be special or general purpose, receiving data and instructions from, and transmitting data and instructions to, a storage system, at least one input device, and at least one output device.

A computer program for implementing the methods of the present invention may be written in any combination of one or more programming languages. These computer programs may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the computer programs, when executed by the processor, cause the functions/acts specified in the flowchart and/or block diagram block or blocks to be performed. A computer program can execute entirely on a machine, partly on a machine, as a stand-alone software package partly on a machine and partly on a remote machine or entirely on a remote machine or server.

In the context of the present invention, a computer-readable storage medium may be a tangible medium that can contain, or store a computer program for use by or in connection with an instruction execution system, apparatus, or device. A computer readable storage medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. Alternatively, the computer readable storage medium may be a machine readable signal medium. More specific examples of a machine-readable storage medium would include an electrical connection based on one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

To provide for interaction with a user, the systems and techniques described here can be implemented on an electronic device having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to a user; and a keyboard and a pointing device (e.g., a mouse or a trackball) by which a user may provide input to the electronic device. Other kinds of devices may also be used to provide for interaction with a user; for example, feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user may be received in any form, including acoustic, speech, or tactile input.

The systems and techniques described here can be implemented in a computing system that includes a back-end component (e.g., as a data server), or that includes a middleware component (e.g., an application server), or that includes a front-end component (e.g., a user computer having a graphical user interface or a web browser through which a user can interact with an implementation of the systems and techniques described here), or any combination of such back-end, middleware, or front-end components. The components of the system can be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include: local Area Networks (LANs), Wide Area Networks (WANs), blockchain networks, and the Internet.

The computing system may include clients and servers. A client and server are generally remote from each other and typically interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other. The server can be a cloud server, also called a cloud computing server or a cloud host, and is a host product in a cloud computing service system, so that the defects of high management difficulty and weak service expansibility in the traditional physical host and VPS service are overcome.

It should be understood that various forms of the flows shown above may be used, with steps reordered, added, or deleted. For example, the steps described in the present invention may be executed in parallel, sequentially, or in different orders, and are not limited herein as long as the desired results of the technical solution of the present invention can be achieved.

The above-described embodiments should not be construed as limiting the scope of the invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions may be made in accordance with design requirements and other factors. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A digital watermark embedding method, comprising:

acquiring an original image and a digital watermark image;

determining at least one watermark embedding area of the original image;

2. The method as claimed in claim 1, wherein the adaptively adjusting, according to the digital watermark image, the brightness of pixel points in the non-overlapping preset pixel regions in the watermark embedding region comprises:

acquiring an original image brightness matrix corresponding to the watermark embedding area, wherein the original image brightness matrix is formed by brightness components of all pixel points in the watermark embedding area of the original image in a YUV color mode;

dividing the original image brightness matrix into a plurality of non-overlapping preset pixel regions;

according to the watermark information in the digital watermark image, carrying out self-adaptive adjustment on the pixel point brightness of each preset pixel region in the original image brightness matrix in sequence to obtain a target image brightness matrix;

and synthesizing the brightness matrix of the target image and the chrominance component of the original image in the watermark embedding area to obtain a digital watermark embedding image.

3. The method according to claim 2, wherein the adaptively adjusting, according to the watermark information in the digital watermark image, the pixel brightness of each preset pixel region in the original image brightness matrix in sequence to obtain a target image brightness matrix comprises:

determining the central brightness value of a central pixel point according to the watermark information corresponding to the preset pixel region, the brightness average value and the embedding step length;

determining a brightness adjustment value of the non-central pixel point according to the watermark information corresponding to the preset pixel area and the embedding step length;

and adjusting the brightness of the central pixel point of the preset pixel area to be the central brightness value, and adjusting the brightness of the non-central pixel point of the preset pixel area based on the brightness adjustment value to obtain a target image brightness matrix.

4. The method according to claim 3, wherein the determining the central luminance value of the central pixel according to the watermark information corresponding to the preset pixel region, the luminance average value, and the embedding step includes:

5. The method according to claim 3, wherein the determining the brightness adjustment value of the non-center pixel according to the watermark information corresponding to the preset pixel region and the embedding step includes:

acquiring the number of non-central pixel points in the preset pixel area;

6. The method of any of claims 1-5, wherein determining at least one watermark embedding region of the original image comprises:

determining a gray scale image of the original image;

determining a minimum perceptible distortion matrix of the gray-scale image through a nonlinear addition masking model, and mapping the minimum perceptible distortion matrix to the gray-scale image to obtain a mapped image;

traversing the mapping image according to a preset sliding template to obtain each alternative area, wherein the size of the preset sliding template is determined by the size of the digital watermark image and the size of the pixels of the preset pixel area;

and determining the candidate area meeting the preset condition as the watermark embedding area.

7. The method according to claim 6, wherein if there are a plurality of candidate regions that satisfy the predetermined condition, each candidate region that satisfies the predetermined condition and that does not overlap with each other is determined as the watermark embedding region.

8. The method of claim 6, wherein determining the minimum perceivable distortion matrix for the grayscale image by a non-linear additive masking model comprises:

9. The method according to any one of claims 1 to 5, wherein the digital watermark image is an image subjected to encryption processing.

10. A method for extracting a digital watermark, comprising:

acquiring a brightness component image and a preset pixel size of a watermark image to be extracted, wherein the watermark image to be extracted is a digital watermark embedded image obtained by adopting the digital watermark embedding method of any one of claims 1 to 9; each pixel point of the brightness component image is the brightness component of each pixel point of the watermark image to be extracted in a YUV color mode; the predetermined pixel size is a pixel size of the predetermined pixel region according to any one of claims 1 to 9;

11. The method of claim 10, wherein the extracting watermark information of each of the target pixel regions comprises:

for each target pixel region, extracting the brightness of each pixel point in the target pixel region;

and determining the watermark information of the target pixel region according to the brightness of each pixel point.

12. The method of claim 11, wherein determining the watermark information of the target pixel region according to the brightness of each pixel point comprises:

13. The method of claim 10, further comprising, after said determining the digital watermark image:

acquiring a key of a digital watermark image embedded in the watermark image to be extracted;

decrypting the digital watermark image based on the key;

14. A digital watermark embedding apparatus, comprising:

15. A digital watermark extraction apparatus, comprising:

an obtaining module, configured to obtain a luminance component image and a preset pixel size of a watermark image to be extracted, where the watermark image to be extracted is a digital watermark embedded image obtained by using the digital watermark embedding method according to any one of claims 1 to 9; each pixel point of the brightness component image is the brightness component of each pixel point of the watermark image to be extracted in a YUV color mode; the predetermined pixel size is a pixel size of the predetermined pixel region according to any one of claims 1 to 9;

16. An electronic device, characterized in that the electronic device comprises:

at least one processor; and

a memory communicatively coupled to the at least one processor; wherein,

the memory stores a computer program executable by the at least one processor, the computer program being executable by the at least one processor to enable the at least one processor to perform the digital watermark embedding method of any one of claims 1-9 and/or to perform the digital watermark embedding method of any one of claims 10-13.

17. A computer-readable storage medium, having stored thereon computer instructions for causing a processor to, when executed, implement the digital watermark embedding method of any one of claims 1-9 and/or implement the digital watermark embedding method of any one of claims 10-13.