Image scrambling and speckle optical watermark information-based hiding method and system

Abstract

The application discloses a hiding method and system based on image scrambling and speckle optical watermark information, and relates to the field of visual cryptography. The method comprises the following steps: acquiring an original image; the original image is a surface texture image of a target paper; performing a pretreatment operation on the original image to obtain a quasi-speckle image; determining a watermark image; the watermark image is a binary image determined according to set watermark information hiding requirements; using a gray scale complementary algorithm to obtain an information hiding image according to the quasi-speckle image and the watermark image; the information hiding image is a quasi-speckle image carrying watermark information; and the application can increase the contrast and improve the key robustness.

Description

Technical Field

[0001] This invention relates to the field of visual cryptography, and in particular to a method and system for hiding information based on image scrambling and speckle optical watermarking. Background Technology

[0002] Visual cryptography (VC) is a secret-sharing scheme proposed by Naor and Shamir in 1995. Building upon this, Sun Xinkai et al. proposed replacing the shared image in visual cryptography with natural speckle patterns, effectively avoiding the problem of insufficient randomness in shared images. The next challenge is how to derive an alternative shared image that also possesses a degree of randomness. Their grayscale rearrangement algorithm produced this alternative image, ensuring sufficient randomness while preventing information leakage, effectively addressing the issue of insufficient randomness in shared images in visual cryptography. However, the watermark information extracted by this method is not clear enough, and the contrast is relatively low.

[0003] Therefore, it is crucial to further enhance the contrast of watermark information and improve the robustness of watermark keys for practical applications in communications, defense, and networks. Summary of the Invention

[0004] The purpose of this invention is to provide a method and system for hiding information based on image scrambling and speckle optical watermarking, which can increase contrast and improve key robustness.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A method for hiding information based on image scrambling and speckle optical watermarking, the method comprising:

[0007] Acquire the original image; the original image is the surface texture image of the target paper;

[0008] The original image is preprocessed to obtain a speckle-like image;

[0009] Determine the watermark image; the watermark image is a binary image determined according to the set watermark information hiding requirements;

[0010] A gray-scale complementary algorithm is used to obtain an information-hidden image based on the speckle-like image and the watermark image; the information-hidden image is a speckle-like image carrying watermark information.

[0011] Optionally, the original image is preprocessed to obtain a speckle-like image, specifically including:

[0012] The original image is cropped according to a set pixel size to obtain a cropped image;

[0013] The cropped image is scrambled to obtain a speckle-like image.

[0014] Optionally, the cropped image is scrambled to obtain a speckle-like image, specifically including:

[0015] A two-dimensional coordinate system is constructed based on two mutually perpendicular boundary lines of the cropped image; the two-dimensional coordinate system includes: a horizontal coordinate axis and a vertical coordinate axis;

[0016] Using the horizontal axis as a reference, the cropped image is subjected to a shear transformation to obtain a sheared image;

[0017] Using the horizontal axis as a reference, the misaligned image is symmetrically transformed to obtain a symmetrical image;

[0018] Using the vertical axis as a reference, the symmetrical image is subjected to a shear transformation to obtain a transformed image;

[0019] The transformed image is subjected to a modulo operation to obtain a scrambled image; the scrambled image is a speckle-like image; the modulo operation is an image cropping and backfilling process.

[0020] Optionally, a gray-level complementary algorithm is used to obtain an information-hidden image based on the speckle-like image and the watermark image, specifically including:

[0021] The pixel sizes of the speckle-like image and the watermark image are set respectively; wherein, the pixel size of the watermark image is set to n×n; the pixel size of the speckle-like image is set to m×m; m=kn, k>1, and k is a positive integer;

[0022] The speckle-like image is divided into n pixel blocks, where each pixel block is a k×k rectangular block; each rectangular block corresponds to each pixel of the watermark image; the rectangular block is a shared image after pixel expansion of the pixel corresponding to the pixel of the watermark image;

[0023] Determine the speckle image segmentation sequence based on all the rectangular blocks;

[0024] Based on the pixel size of the watermark image, the watermark image is segmented to obtain a watermark image segmentation sequence;

[0025] Based on the spotted image segmentation sequence and the watermark image segmentation sequence, for the i-th element at the same position, grayscale value calculation is performed on the spotted image segmentation sequence and the watermark image segmentation sequence according to the set processing method to obtain a grayscale value sequence; where i≥1;

[0026] If i≤n 2 If the i+1th element is obtained, the grayscale value calculation process continues.

[0027] if i>n 2 Then the gray value sequence is output to obtain the gray value corresponding to each pixel block;

[0028] The information-hiding image is determined based on the grayscale value corresponding to each pixel block.

[0029] Optionally, the method further includes:

[0030] Based on the speckle-like image and the information-hidden image, an optical image reconstruction operation is performed to obtain the watermark image.

[0031] Optionally, an optical image reconstruction operation is performed based on the speckle-like image and the information-hiding image to obtain the watermark image, specifically including:

[0032] A spatial light modulator is used to determine a first hologram based on the speckle-like image, and a second hologram is determined based on the information-hidden image;

[0033] The first hologram is optically modulated using an optical wave modulation method to obtain a first modulated image;

[0034] The second hologram is optically modulated using an optical wave modulation method to obtain a second modulated image;

[0035] The first modulation image is reproduced using a Fourier lens to obtain the first reproduced image;

[0036] The second modulation image is reproduced using a Fourier lens to obtain the second reproduced image;

[0037] Based on the first reproduced image and the second reproduced image, an incoherent superposition is performed to obtain a watermark image.

[0038] A hiding system based on image scrambling and speckle optical watermarking information, the system comprising:

[0039] The image acquisition module is used to acquire the original image; the original image is the surface texture image of the target paper.

[0040] The preprocessing module is used to perform preprocessing operations on the original image to obtain a speckle-like image;

[0041] A watermark image determination module is used to determine a watermark image; the watermark image is a binary image determined according to the set watermark information hiding requirements.

[0042] The hiding module is used to obtain an information hiding image based on the speckle-like image and the watermark image using a gray-scale complementary algorithm; the information hiding image is a speckle-like image carrying watermark information.

[0043] An electronic device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the above-described method for hiding information based on image scrambling and speckle optical watermarking.

[0044] A computer-readable storage medium storing a computer program that, when executed, implements the above-described hiding method based on image scrambling and speckle optical watermarking information.

[0045] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0046] This invention provides a method and system for hiding optical watermark information based on image scrambling and speckle. The method involves acquiring an original image (a surface texture image of the target paper), preprocessing the original image to obtain a speckle-like image, determining a watermark image (a binary image determined according to set watermark information hiding requirements), and using a grayscale complementary algorithm to obtain an information-hiding image based on the speckle-like image and the watermark image. The information-hiding image is a speckle-like image carrying watermark information. Therefore, this method increases contrast and improves key robustness. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 A flowchart of a method for hiding information based on image scrambling and speckle optical watermarking provided in an embodiment of the present invention;

[0049] Figure 2 This is a process diagram of scrambling operation provided in an embodiment of the present invention;

[0050] Figure 3 This is a diagram showing the result of a scrambling operation provided in an embodiment of the present invention;

[0051] Figure 4 A flowchart illustrating the gray-scale complementary algorithm provided in this embodiment of the invention;

[0052] Figure 5A schematic diagram of a surface texture image provided in an embodiment of the present invention;

[0053] Figure 6 This is a schematic diagram of a cropped image provided in an embodiment of the present invention;

[0054] Figure 7 This is a schematic diagram of watermark information provided in an embodiment of the present invention;

[0055] Figure 8 This is a schematic diagram of the simulated watermark information extraction image provided in an embodiment of the present invention;

[0056] Figure 9 This is a schematic diagram of the simulated watermark information extraction image provided in an embodiment of the present invention;

[0057] Image 10 is a schematic diagram of an image after incoherent overlay processing provided in an embodiment of the present invention;

[0058] Figure 11 A schematic diagram illustrating the process of obtaining the watermark carrier and generating the watermark key;

[0059] Figure 12 This is a schematic diagram illustrating the process of extracting watermark information. Detailed Implementation

[0060] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0061] Using a gray-scale complementary algorithm to calculate the watermark key ensures that the gray values ​​of the superimposed watermark information remain consistent, greatly increasing the contrast. This also improves the robustness of the watermark key to a certain extent, and its practicality has broad prospects in communications, defense, and networks.

[0062] The purpose of this invention is to provide a method and system for hiding information based on image scrambling and speckle optical watermarking, which can increase contrast and improve key robustness.

[0063] Image scrambling refers to the systematic scrambling of pixels in an image, using the Fibonacci scrambling method. Visual cryptography is a hiding technique that can be directly decoded by human vision. The simplest sharing scheme represents the secret information as a binary image of black and white pixels, and distributes each original pixel into n shared images, each containing m sub-pixels. These shared images are printed on transparent films, where the black and white pixels are highly similar. By superimposing these transparent films, the human visual system can perceive the superimposed state of all shared images as an average of black or white contributions, thus identifying the hidden secret information.

[0064] Speckle optical watermarking is an improvement on visual cryptography. Given a specific speckle image with a discrete grayscale gradient distribution, it serves as the watermark carrier. A grayscale rearrangement algorithm is used to obtain the watermark key, which is also discretely distributed with a grayscale gradient. By incoherently superimposing the two images, the watermark information can be directly identified by the human eye and extracted.

[0065] To further improve the contrast of speckle optical watermarking, a gray-level complement algorithm is proposed for calculating the watermark key. This algorithm generates the watermark key image by calculating the average gray level of the watermark carrier. The watermark information is then obtained by incoherently superimposing the watermark carrier image and the watermark key. The superimposed watermark information has consistent gray levels, which is visually distinct from the surrounding information, significantly improving the contrast of the watermark information.

[0066] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0067] Example 1

[0068] like Figure 1 As shown, embodiments of the present invention provide a hiding method based on image scrambling and speckle optical watermarking information, the method comprising:

[0069] Step 100: Obtain the original image. The original image is the surface texture image of the target paper.

[0070] Step 200: Perform preprocessing operations on the original image to obtain a speckle-like image.

[0071] The preprocessing of the original image to obtain a speckle-like image includes:

[0072] The original image is cropped according to a set pixel size to obtain a cropped image; the cropped image is then scrambled to obtain a speckle-like image.

[0073] The cropped image is scrambled to obtain a speckle-like image, specifically including:

[0074] A two-dimensional coordinate system is constructed based on two mutually perpendicular boundary lines of the cropped image. The two-dimensional coordinate system includes an abscissa axis and a ordinate axis. Using the abscissa axis as a reference, the cropped image is subjected to a shear transformation to obtain a sheared image. Using the abscissa axis as a reference, the sheared image is subjected to a symmetric transformation to obtain a symmetrical image. Using the ordinate axis as a reference, the symmetrical image is subjected to a shear transformation to obtain a transformed image. A modulo operation is performed on the transformed image to obtain a scrambled image. The scrambled image is a speckle-like image. The modulo operation is used for image cropping and backfilling.

[0075] Step 300: Determine the watermark image. The watermark image is a binary image determined according to the set watermark information hiding requirements.

[0076] Step 400: Using a gray-level complementary algorithm, an information-hidden image is obtained based on the speckle-like image and the watermark image. The information-hidden image is a speckle-like image carrying watermark information.

[0077] Specifically, a gray-level complementary algorithm is used to obtain an information-hidden image based on the speckle-like image and the watermark image, including:

[0078] The pixel sizes of the speckle-like image and the watermark image are set respectively; the pixel size of the watermark image is set to n×n; the pixel size of the speckle-like image is set to m×m; m=kn, k>1, and k is a positive integer.

[0079] The speckle-like image is divided into n pixel blocks, where each pixel block is a k×k rectangular block; each rectangular block corresponds to each pixel of the watermark image; the rectangular block is a shared image after the pixel of the watermark image is expanded.

[0080] Determine the speckle image segmentation sequence based on all the rectangular patches.

[0081] Based on the pixel size of the watermark image, the watermark image is segmented to obtain a watermark image segmentation sequence.

[0082] Based on the speckle image segmentation sequence and the watermark image segmentation sequence, for the i-th element at the same position, grayscale value calculation is performed on the speckle image segmentation sequence and the watermark image segmentation sequence according to the set processing method to obtain a grayscale value sequence; where i≥1.

[0083] If i≤n 2 If the i+1th element is obtained, the grayscale value calculation process continues.

[0084] if i>n 2 Then the grayscale value sequence will be output to obtain the grayscale value corresponding to each pixel block.

[0085] The information is hidden in the image based on the grayscale value corresponding to each pixel block.

[0086] As an optional implementation, the method further includes: performing an optical image reconstruction operation based on the speckle-like image and the information-hiding image to obtain a watermark image.

[0087] The process of extracting watermark information requires completely overlapping two images of the same size in order to extract the secret information completely and correctly.

[0088] Specifically, optical image reconstruction is performed based on the speckle-like image and the information-hidden image to obtain the watermarked image, including:

[0089] A spatial light modulator is used to determine the first hologram based on a speckle-like image, and the second hologram is determined based on an information-hidden image.

[0090] The first hologram is modulated by optical waves to obtain the first modulated image.

[0091] The second hologram is modulated using optical wave modulation to obtain the second modulated image.

[0092] The first modulated image is reproduced using a Fourier lens to obtain the first reproduced image.

[0093] The second modulation image is reproduced using a Fourier lens to obtain the second reproduced image.

[0094] Based on the first and second reproduced images, incoherent superposition is performed to obtain the watermark image.

[0095] In practical applications, the hiding method based on image scrambling and speckle optical watermarking information provided in this embodiment of the invention may further include the following specific steps:

[0096] Step 1: Acquire the original image and preprocess it.

[0097] First, a camera is used to capture the surface texture of the paper, which is then transferred to a computer for processing. The image is first cropped into an n×n pixel image S, and then scrambled. The scrambled image S is a speckle-like image B. The scrambling method used for image S is Fibonacci scrambling. The purpose of Fibonacci scrambling is to change the positional relationship of the image pixels, making the grayscale of the scrambled image B appear uniformly distributed. This greatly increases the imperceptibility of embedding a watermark.

[0098] The principle of Fibonacci scrambling is to first perform a shear transformation along the x-axis, then a symmetric transformation along the x-axis, followed by a shear transformation along the y-axis. The final modulus operation is equivalent to a cut-and-fill operation. The transformations are as follows: Figure 2 As shown. For example, the results of scrambling the Lena image once and twice with Fibonacci are as follows. Figure 3 As shown.

[0099] Step 2: Obtain the watermark key using the gray-scale complementary algorithm.

[0100] After obtaining image B, it is fed together with watermark image A (which is any binary image that you want to hide) into a grayscale complementary algorithm (GCA) using a computer. After passing through GCA, the desired image C can be obtained. The grayscale distribution of image B and image C is similar.

[0101] When processing the watermark image A, it is set to an n×n pixel size as needed, while the pixel size of B is m×m (m = kn, where k is a positive integer and k>1). Each pixel in watermark image A corresponds to a k×k pixel block in B, thus dividing B into k×k rectangular blocks. Each rectangular block is equivalent to an expanded version of a pixel in watermark image A. The grayscale distribution of these rectangular blocks is not a strictly binary distribution like that of a visual cryptography key; it is a discrete random distribution. The watermark image A can be extracted by incoherently superimposing C and B, calculated using GCA. This watermark image is directly obtained by the human visual system, and extraction only requires the incoherent superposition of the two images. Therefore, extraction is very convenient even for users without any optical knowledge.

[0102] In computer processing, the watermark image is inserted into the carrier image using the grayscale complementary algorithm (GCA). The goal of GCA is to generate an image C carrying the watermark information, which is both difficult to detect and reliable. Unlike visual cryptography, the output image of GCA is the image C carrying the watermark information, while the input of the algorithm includes the watermark image and image B.

[0103] In GCA, each pixel of the watermarked image corresponds to a pixel block in image B. Assume the number of pixels in watermarked image A and image B are n×n and m×m respectively (m = kn, where k is a positive integer and k > 1). Dividing image B into n² pixel blocks, each containing k² pixels, produces a sequence with n² elements. Each Bi has a pixel block size of k×k. Therefore, the watermark image A is divided into a sequence of n² elements by pixels to obtain... T A Each element in T corresponds to B The elements in T represent the pixels that each pixel block corresponds to at the same location in the watermark image. B The elements in the code are the smallest units of the GCA, and each pixel block will be determined according to T. A Perform different operations on the corresponding elements in the table.

[0104] Let C represent pixels of the same size as B. Segment C in the same way to obtain... C i By B i and A i Therefore, a pixel block processing function R(·) is introduced, with C i =R(B i A i Using R(·), the algorithm's framework is as follows: Figure 4 As shown on the left. Based on the above description, the specific process of GCA is as follows:

[0105] Step 1 Input an image B of size m×M and a binary pattern A of size n×n (m=kn, where k is a positive integer and k>1).

[0106] Step 2: Split B and A to generate sequences TB and TA, and set i to 1;

[0107] Step 3 If i≤n 2 If the result is positive, proceed to step 4; otherwise, proceed to step 5.

[0108] Step 4: Calculate C i =R(B i A i ), where R(B i A i ) is the defined processing function; details are as follows: Figure 4 As shown on the right, i = i + 1, proceed to step 3.

[0109] The processing procedure of the processing function can be explained as follows:

[0110] The average gray value of image B is calculated to be equal to H; when A i When C equals 1, i The grayscale value is equal to B. i The grayscale value; when A i When C equals 0, i The grayscale value of each pixel in the pixel block is equal to twice H minus B. i The grayscale value of each pixel in a pixel block.

[0111] Step 5 Output T C And obtain image C.

[0112] Figure 4 The right side shows R(B) i A i Details of the operation. The operation for each pixel block is related to the corresponding pixel. For each pixel block, there are two steps to generate the processed pixel block. To illustrate the specific process, it is assumed that all pixel blocks contain 3×3 pixels. R(B i A i The definition of ) is as follows Figure 4 As shown on the right. The value of Ai determines R(B) i A i The value of ), assuming the average gray level of B is H, when A i When C = 1, i =R(B i A i )=R(B i ,1)=B i ; when A i When C = 0, i =R(B i A i )=R(B i ,0)=2H-B i Finally, the blocks corresponding to white pixels will remain unchanged, while other blocks will be significantly adjusted. All blocks will be processed and arranged in the appropriate order to form image C carrying the watermark information.

[0113] Step 3: The process of extracting watermark information.

[0114] Images B and C are saved as BMP format images. When extracting watermark information, images B and C are input into two spatial light modulators respectively for optical image reproduction. The watermark information can be obtained by using a CCD to receive both images simultaneously.

[0115] Image B is imported into the spatial light modulator. A hologram of image B is calculated within the spatial light modulator. Light waves are modulated on the liquid crystal surface of the spatial light modulator, and after passing through a Fourier lens, image B can be reproduced in the form of light intensity. The online process for image C is the same as that for image B.

[0116] Regarding holograms:

[0117] The spatial light modulator software has a built-in algorithm for calculating holograms, which can be used to calculate holograms of any image.

[0118] Optical modulation:

[0119] When parallel light shines on a liquid crystal, it is reflected. When reflected, the liquid crystal molecules will form different angles between the liquid crystal molecules and the electric field on the entire liquid crystal screen according to the hologram. That is, the director of the liquid crystal molecules and the polarization direction of the incident light form a certain angle, thereby changing the effective refractive index of the liquid crystal and changing the optical path length of the incident light, thus achieving the process of light wave modulation.

[0120] Fourier lens:

[0121] When placing a Fourier lens, its front focal plane needs to be at the position of the LCD screen and its rear focal plane needs to be at the position of the CCD in order to reproduce a clear image.

[0122] Example 2

[0123] This invention provides a hiding system based on image scrambling and speckle optical watermarking information. The system includes: an image acquisition module, a preprocessing module, a watermark image determination module, and a hiding module.

[0124] The image acquisition module is used to acquire the original image; the original image is the surface texture image of the target paper.

[0125] The preprocessing module is used to perform preprocessing operations on the original image to obtain a speckle-like image.

[0126] The watermark image determination module is used to determine the watermark image; the watermark image is a binary image determined according to the set watermark information hiding requirements.

[0127] The hiding module is used to obtain an information-hiding image based on the speckle-like image and the watermark image using a gray-level complementary algorithm; the information-hiding image is a speckle-like image carrying watermark information.

[0128] Example 3

[0129] This invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the hiding method based on image scrambling and speckle optical watermarking information in Embodiment 1.

[0130] As an alternative implementation, a computer-readable storage medium is also provided, on which a computer program is stored, which, when executed, implements the hiding method based on image scrambling and speckle optical watermarking information in Embodiment 1.

[0131] Example 4

[0132] In practical applications, a Canon 60D camera is used to capture the surface of paper, obtaining an image of the paper's surface texture, such as... Figure 5As shown, the image size is 5184×3456. After being transferred to the computer, it is cropped to a size of 1024×1024 pixels. Image 6 is then subjected to 200 Fibonacci scrambling operations on the cropped image. Figure 8 . Figure 7 For watermark information with a pixel size of 512×512, Figure 7 and Figure 8 The input is fed into GCA, and the output is a pixel size of 1024×1024. Figure 9 The extraction of simulated watermark information is then... Figure 8 and Figure 9 Incoherent superposition is obtained Figure 10 The process of obtaining the watermark carrier and generating the watermark key is as follows: Figure 11 As shown.

[0133] The process of extracting watermark information using this hidden scheme is as follows: Figure 12 As shown. The light beam is split into two beams after passing through beam splitter 1. The beam split into the x-direction passes through polarizer 1 and beam splitter 2 and then illuminates spatial light modulator 1. Spatial light modulator 1 loads image B and reflects the modulated beam back to beam splitter 2. After reflection by beam splitter 2, the beam passes through Fourier lens 1 and beam splitter 4 and is received by the CCD camera with an amplitude of B(x). B y B The beam split in the y-direction passes through polarizer 2 and beam splitter 3, then illuminates spatial light modulator 2. Spatial light modulator 2, loaded with image C, reflects the modulated beam back to beam splitter 3. After passing through beam splitter 3, Fourier lens 2, and beam splitter 4, the amplitude received by the CCD camera is C(x). C y C The watermark information D(x) can be recovered by superimposing the two modulated light beams on the receiving surface of the CCD camera. D y D ):

[0134] B(x B y B )+C(x C y C )=D(x D y D ).

[0135] The reconstruction process of image B: The plane wave shines on the beam splitter prism 1 and is reflected. The reflected portion is converted into linearly polarized light by the polarizer 1. The light then shines on the liquid crystal screen of the spatial light modulator 1 through the beam splitter prism 2. The liquid crystal screen modulates the linearly polarized light at various positions according to the different distribution of the hologram of image B and reflects it. After being reflected by the beam splitter prism 2, the polarized light is modulated again by the Fourier lens 1. This is equivalent to the light field distribution undergoing a Fourier transform. After that, the light wave passes through the beam splitter prism 4 and is received by the CCD to reconstruct the amplitude of image B′.

[0136] The reconstruction process of image C: The portion of the plane wave that hits the beam splitter 1 is converted into linearly polarized light by the polarizer 2. The light is then reflected by the beam splitter 3 and falls onto the liquid crystal screen of the spatial light modulator 2. The liquid crystal screen modulates the linearly polarized light at various positions based on the different distribution of the hologram of image C and reflects it. The light then passes through the beam splitter 2 and reaches the Fourier lens 2. The polarized light is modulated again by the Fourier lens 2 (equivalent to a Fourier transform of the light field distribution). After that, the light wave is reflected by the beam splitter 4 and received by the CCD to reconstruct the amplitude of image C′.

[0137] The main indicators for evaluating optical information hiding schemes are generally: security, imperceptibility, and robustness.

[0138] 1. Imperceptibility: Image B was obtained by scrambling paper and contains no perceptible information. Image C was obtained using a gray-level complement algorithm; its difference from Image B lies in the fact that some gray levels are complementary to its image, and it also does not carry any perceptible information. The gray-level histograms of Images B and C were calculated separately, and it was found that their gray-level histograms approximate a normal distribution. The mean and variance of their gray-level histograms were then calculated, and the difference was less than 0.1%. Next, subsets of Image C at different positions and sizes were taken, and their mean and variance were calculated and compared with the gray-level histogram of Image C; the difference was less than 0.3%. This indicates that the human eye cannot detect the watermark information hidden in the carrier image under normal circumstances.

[0139] 2. Security: Obtaining watermark information requires incoherent overlay of two images, which necessitates maintaining consistent size and angle; otherwise, watermark acquisition will fail. In summary, this system boasts high security, requiring precise parameters to ensure image recovery.

[0140] 3. Robustness: The robustness analysis of this scheme was conducted using computer simulation. For watermarking systems, some effects caused during the extraction process can be attributed to noise interference; therefore, noise is added to the visual key used for extraction. Taking Gaussian noise as an example, the added noise amplitude is 0.5 times the watermark amplitude, and then the image is incoherently superimposed. Through simulation analysis, it is verified that the recovered watermark information can still be identified, demonstrating the strong noise resistance of this system.

[0141] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0142] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for hiding image information based on image scrambling and speckle optical watermarking, characterized in that, The method includes: Acquire the original image; the original image is the surface texture image of the target paper; The original image is preprocessed to obtain a speckle-like image; Determine the watermark image; the watermark image is a binary image determined according to the set watermark information hiding requirements; A gray-scale complementary algorithm is used to obtain an information-hidden image based on the speckle-like image and the watermark image; the information-hidden image is a speckle-like image carrying watermark information. Using a gray-level complementary algorithm, an information-hidden image is obtained based on the speckle-like image and the watermark image, specifically including: The pixel sizes of the speckle-like image and the watermark image are set respectively; wherein, the pixel size of the watermark image is set to n×n; the pixel size of the speckle-like image is set to m×m; m=kn, k>1, and k is a positive integer; The speckle-like image is divided into n pixel blocks, where each pixel block is a k×k rectangular block; each rectangular block corresponds to each pixel of the watermark image; the rectangular block is a shared image after pixel expansion of the pixel corresponding to the pixel of the watermark image; Determine the speckle image segmentation sequence based on all the rectangular blocks; Based on the pixel size of the watermark image, the watermark image is segmented to obtain a watermark image segmentation sequence; Based on the spotted image segmentation sequence and the watermark image segmentation sequence, for the i-th element at the same position, grayscale value calculation is performed on the spotted image segmentation sequence and the watermark image segmentation sequence according to a set processing method to obtain a grayscale value sequence; where i≥1; If i≤n 2 If the i+1th element is obtained, the grayscale value calculation process continues. if i>n 2 Then the gray value sequence is output to obtain the gray value corresponding to each pixel block; The information-hiding image is determined based on the grayscale value corresponding to each pixel block.

2. The method for hiding information based on image scrambling and speckle optical watermarking according to claim 1, characterized in that, The original image is preprocessed to obtain a speckle-like image, specifically including: The original image is cropped according to a set pixel size to obtain a cropped image; The cropped image is scrambled to obtain a speckle-like image.

3. The method for hiding information based on image scrambling and speckle optical watermarking according to claim 2, characterized in that, The cropped image is scrambled to obtain a speckle-like image, specifically including: A two-dimensional coordinate system is constructed based on two mutually perpendicular boundary lines of the cropped image; the two-dimensional coordinate system includes: a horizontal coordinate axis and a vertical coordinate axis; Using the horizontal axis as a reference, the cropped image is subjected to a shear transformation to obtain a sheared image; Using the horizontal axis as a reference, the misaligned image is symmetrically transformed to obtain a symmetrical image; Using the vertical axis as a reference, the symmetrical image is subjected to a shear transformation to obtain a transformed image; The transformed image is subjected to a modulo operation to obtain a scrambled image; the scrambled image is a speckle-like image; the modulo operation is an image cropping and backfilling process.

4. The method for hiding information based on image scrambling and speckle optical watermarking according to claim 1, characterized in that, The method further includes: Based on the speckle-like image and the information-hidden image, an optical image reconstruction operation is performed to obtain the watermark image.

5. The method for hiding information based on image scrambling and speckle optical watermarking according to claim 4, characterized in that, Based on the speckle-like image and the information-hidden image, an optical image reconstruction operation is performed to obtain the watermark image, specifically including: A spatial light modulator is used to determine a first hologram based on the speckle-like image, and a second hologram is determined based on the information-hidden image; The first hologram is optically modulated using an optical wave modulation method to obtain a first modulated image; The second hologram is optically modulated using an optical wave modulation method to obtain a second modulated image; The first modulation image is reproduced using a Fourier lens to obtain the first reproduced image; The second modulation image is reproduced using a Fourier lens to obtain the second reproduced image; Based on the first reproduced image and the second reproduced image, an incoherent superposition is performed to obtain a watermark image.

6. A hiding system based on image scrambling and speckle optical watermarking information, characterized in that, The system includes: The image acquisition module is used to acquire the original image; the original image is the surface texture image of the target paper. The preprocessing module is used to perform preprocessing operations on the original image to obtain a speckle-like image; A watermark image determination module is used to determine a watermark image; the watermark image is a binary image determined according to the set watermark information hiding requirements. The hiding module is used to obtain an information-hiding image based on the speckle-like image and the watermark image using a gray-level complementary algorithm; the information-hiding image is a speckle-like image carrying watermark information. Using a gray-level complementary algorithm, an information-hidden image is obtained based on the speckle-like image and the watermark image, specifically including: The pixel sizes of the speckle-like image and the watermark image are set respectively; wherein, the pixel size of the watermark image is set to n×n; the pixel size of the speckle-like image is set to m×m; m=kn, k>1, and k is a positive integer; The speckle-like image is divided into n pixel blocks, where each pixel block is a k×k rectangular block; each rectangular block corresponds to each pixel of the watermark image; the rectangular block is a shared image after pixel expansion of the pixel corresponding to the pixel of the watermark image; Determine the speckle image segmentation sequence based on all the rectangular blocks; Based on the pixel size of the watermark image, the watermark image is segmented to obtain a watermark image segmentation sequence; Based on the spotted image segmentation sequence and the watermark image segmentation sequence, for the i-th element at the same position, grayscale value calculation is performed on the spotted image segmentation sequence and the watermark image segmentation sequence according to a set processing method to obtain a grayscale value sequence; where i≥1; If i≤n 2 If the i+1th element is obtained, the grayscale value calculation process continues. if i>n 2 Then the gray value sequence is output to obtain the gray value corresponding to each pixel block; The information-hiding image is determined based on the grayscale value corresponding to each pixel block.

7. An electronic device, characterized in that, The method includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the hiding method based on image scrambling and speckle optical watermarking information as described in any one of claims 1 to 5.

8. A computer-readable storage medium, characterized in that, The storage medium stores a computer program, which, when executed, implements the hiding method based on image scrambling and speckle optical watermarking information as described in any one of claims 1 to 5.

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