CN1691087A - System and method for decoding digital coding image - Google Patents

Abstract

The invention provides a method of decoding coding image produced by main image and at least one auxiliary image utilizing at least one coding parameter. The said coding image is formed as the following method: when printing the coding image, the viewers can not distinguish the auxiliary image without an optics decoding device which has the corresponding characteristic with at least one coding parameter. The said method includes: obtaining the digital edition of the said coded image; confirming at least one code parameter mentioned above; and utilizing at least one code parameter in the said code population of parameters to make up the decoding image of the said digital coding image.

Description

The system and method that is used for decoding digital coding image

The cross reference of related application

The application requires the U.S. Provisional Application NO.60/565 of submission on April 26th, 2004, and 300 right of priority is all open in the lump as a reference with it here.The U. S. application NO.10/847 that this application also relates on May 18th, 2004 to be submitted to, 962 (' 962 applications) and the U. S. application NO.10/897 that submitted on May 18th, 2004,943 (' 943 applications), here that it is all open in the lump as a reference.

Technical field

The present invention relates generally to counterfeit protection field, more specifically, relates to by using coded image to carry out the field of electronics and document printing protection.

Background technology

The trend that is occurred in the ecommerce world that makes rapid progress is for using WWW and Email, to provide up-to-date business document to consumer and other terminal temperature difference.The robotization document generates and electron distributions, such as using Email or web services, has many advantages.This has reduced the cost that is associated with pre-print form, document filing, mailing, processing etc. significantly.It makes the industry user can immediately visit significant data, and document the clock round ground can be used the client all the time.Yet there is some defective in electronic document, comprising: distort or be created in the possibility that great majority or whole aspect are similar to the duplicity document of original paper.

Propose many Software tools and protected the integrality and the confidentiality of electronic document.Can provide control widely to adding or revising the record in the electronic document and form field, file encryption and add digital signature such as such instruments such as plug-in card programs to document.

Typically, be used to protect the remarkable shortcoming with the safeguard measure of the document of electronic form setting to be: in case document is sent to print media, these measures often are useless.In addition, typical hard copy safeguard measure is disabled for the recipient of electronic document.For example, safety ink or paper are available for document creator, and are disabled for the electric transmission file receiver.Significantly, when document creator can not be controlled print procedure, keep the security existing problems of the hard copy of electric transmission copy.In addition, can use many desktop pictures software for editing instrument to create the forgery printout of very complicated electronic document.Document printing also is widely used in many aspects of daily life, comprises commercial affairs and government facility.

The widely used guard method that stops numeral forgery and recognition data to change comprises bar code and digital watermarking.Usually, by the initiator these are added in the document as image file.Yet it is general available that bar code generates software, and can the person of being forged be used to create the duplicity document.

Digital watermarking has been proposed as solution, but test shows: it may be lack of consistency and be extensive use of required reliability.In addition, it is very expensive usually to implement this technology, and the equipment cost that is used for essential hardware and software has been offset the cost savings that distribute and realize by electronic document sometimes.Usually, the quantity of information that can be protected can be confined to only several numerals or letter.These problems have caused serious constraint to the reliability and the usability of electronic document in commercial and service.

The forgery of document printing and change and the black market sale of counterfeiting merchandise are the prominent questions that systematicness faced that the world of today increases day by day.Annual because the duplicity of non-true document and brand article is used, lost millions of dollar.Photoscanner, duplicating machine and be used for improving day by day of copy item purpose miscellaneous equipment and constantly strengthened adulterator's ability are produced and are had enough qualities and usually can't detected duplicity document and other counterfeit.

Realize protection to document by using coded image.Typically, under the situation that does not have special optical decoder device, can't differentiate or image that decipher is such.In fact, can use it on any type of document printing, comprise law documentation, I.D. and paper spare, label, packing, currency, stamp etc.It is conspicuous using the value of not reproducible coded image on such as documents such as pilot's certificate and vehicle titles.In addition, use it for packing and go up the method for counterfeiting merchandise, also have higher value as identification.

The use of coded image has greatly strengthened document and the own ability through the document that changes of forging that detect.Yet, exist and use the optical decoder device to detect the unpractical situation of coded image.Existing wherein even before document is printed needs to use coded image to protect other situations of document.In this two classes situation (and other situation), extremely need to have the demoder that is used for decoding digital coding image based on numeral or software.Also may need the use of coded image and the use of other safeguard measure are combined.

Summary of the invention

The present invention proposes a kind of data handling system and method that is used for decoding digital coding image.A scheme of the present invention has proposed a kind of at least one coding parameter that utilizes and has decoded by the method for master image with the coded image of at least one assistant images generation.Form described coded image in such a way: when printed encoded image, if do not have optical decoder equipment with described at least one coding parameter corresponding characteristic, then the beholder can't distinguish assistant images.Described method comprises: the digital version that obtains described coded image; Determine described at least one coding parameter; And utilize at least one coding parameter in the described coding parameter group, according to described digital coding image structure decoded picture.

Another program of the present invention has proposed a kind of method that is used to strengthen to the protection of the digital document that wherein embedded first coded image, described first coded image that utilized the checking content group and the first coding parameter set constructor.Described method comprises: utilize the described first coding parameter group that described first coded image is carried out digital decoding, to produce decoded picture; From described decoded picture, extract described checking content group.Then, utilize described checking content group and the second coding parameter set constructor, second coded image.

Description of drawings

By reading following description and accompanying drawing, the present invention will more fully be understood, and in the accompanying drawings, use identical reference symbol to represent identical assembly, wherein:

Fig. 1 is to use the decode figure of printed encoded image of optical decoder device;

Fig. 2 is the figure of the typical rasterisation coded image that utilizes the grating conversion method, formed by master image and assistant images;

Fig. 3 is to use the decode figure of coded image shown in Figure 2 of optical decoder device;

Fig. 4 is the figure of blank (blank control) image with periodically variable tonal density;

Fig. 5 is the figure that embeds assistant images in contrast image shown in Figure 4;

Fig. 6 is the coded image that is formed by master image and contrast image shown in Figure 5;

Fig. 7 is according to embodiments of the invention, the process flow diagram of the method for decoding digital image;

Fig. 8 is according to embodiments of the invention, the process flow diagram of the method for decoding digital image;

Fig. 9 is according to embodiments of the invention, the process flow diagram of the method for decoding digital image;

Figure 10 is the synoptic diagram to the coded image sampling;

Figure 11 is the synoptic diagram according to the composograph of coded image sample formation shown in Figure 10;

Figure 12 is according to embodiments of the invention, the process flow diagram of the method for protection and checking digital document;

Figure 13 is the synoptic diagram that is used for according to the system of embodiments of the invention protection and checking digital document;

Figure 14 is the synoptic diagram that is used for according to the system of embodiments of the invention protection and checking digital document;

Figure 15 is according to embodiments of the invention, the process flow diagram of the method for protection and checking digital document.

Embodiment

The present invention proposes the method that is used for decoding digital coding image, and need not to use the physical optics decoding device.Can use these methods to decode digital coding image of never printing and the printed encoded image that has scanned or be converted to digital form by other device.The ability of decoding digital image allows the user to prevent distorting of document with numeral and print form, therefore, bridge joint numeral arrive the border of paper.Coded image is verified and revised in different phases such as electronic document generation, transmission and printings by allowing, extra security also is provided.

Embodiments of the invention relate to the method for utilizing the optical encoding image to protect document and other project.Typically, these images are embedded in background or the source images and with it are printed on the clauses and subclauses that may be changed, distort or forge.As used herein, term " coded image " relates to processed in the following manner or is hidden in background field or the interior image of another image: when using or print, under the situation of not using decoding device, human eye can not be distinguished coded image.Some coded images are hidden, thereby be difficult to from background or master image, distinguish its existence.Other coded images are visible easily, but not readable, and this is because picture material has been carried out system's scrambling or other processing.

The encoded image that the present invention is had special importance is to be configured to utilize biconvex lens to carry out those images of optical decoder.The ability of this imagery exploitation biconvex lens is come the masked images content according to the lenticule frequency of lens.Typically, these images are encoded, relate to: set up the regularization periodic pattern have with the corresponding frequency of biconvex lens that will use as demoder, then, cause pattern deformation, make this image be difficult to the naked eye distinguish by one of a plurality of methods.Can utilize special-purpose camera installation, form this type of coded image with analog form, as United States Patent (USP) NO.3, in 937,565 disclosed like that, or form this type of coded image with digital form, as United States Patent (USP) 5, disclosed such in 708,717 (' 717 patents), here that it is all open in the lump as a reference.

Digital coding image can be embedded in the background or in other image graph picture, thereby be difficult to distinguish the existence of coded image.With reference to figure 1, can utilize master or source images 20 and the assistant images 40 that is embedded in the master image 20 to form coded image 10, in such a manner, only can utilize the decoding device 40 of preset frequency to watch assistant images 40.Master image can be blank grey or color background image, and coded image 10 as shown in Figure 1 is such, maybe can comprise the visual image contents such as mark such as pattern or photo or any other form.In addition, assistant images can be any type of image or mark, and can comprise relevant with master image in some aspects mark.In example codes image 10, assistant images 40 is based on the repeat patterns of word " Department of Transportation ".Can encode separately to assistant images, then, incorporate into or be embedded in the master image, or can be according to when embedding assistant images, its mode of encoding being realized embedding processing.As shown in Figure 1, can be by placing coded image 10 tops to watch assistant images decoding device 40 with suitable direction.In the example of Fig. 1, decoding device has transverse axis 32 and Z-axis 34, and coded image 10 has transverse axis 22 and Z-axis 24.When the transverse axis 32 of decoding device 40 when directed with respect to the decoding angle [alpha] of the transverse axis 22 of coded image 10, appeared assistant images 40.The decoding angle [alpha] be assistant images is encoded and embed before the coding parameter set up.

The method of utilizing it that assistant images is embedded into or to merge to master image can be divided into two conventional methods.In first method, regularization cyclophysis (behaviour) is forced at the master image of using preset frequency.This is mainly by realizing with preset frequency rasterisation master image.Then, assistant images is mapped to master image, thus can with the assistant images that comprises picture material in corresponding position, position change the regularization characteristic of master image.Though change for a short time, make it be difficult to distinguish by human eye.Yet when having biconvex lens with the corresponding frequency of preset frequency when placing the master image top, it will shield primary image content according to extracting this changes to form the mode of hiding assistant images.

In second method, at first, the regularization cyclophysis is forced at assistant images, rather than master image, as long as there is the position of content in assistant images, the change of this characteristic will appear.Then, assistant images is mapped to master image, and, changes the content of master image by pixel according to the content of the assistant images of encoding.

Now, the example of said method will be discussed in more detail.A simplified example of first method has been shown among Fig. 2-3.Fig. 2 shows the enlarged drawing of optical encoding image 110.Coded image 110 is made of the assistant images of people's face master image and letter " SI ".With particular mask frequency and grating angle [alpha] rasterisation master image.By introducing the position change (change) of raster element, assistant images is embedded in the master image with the corresponding position of the content of assistant images.Can make these changes enough little, thereby be difficult to that naked eyes are interpreted this as and be embedded in the interior poly-image in the master image.Progressive as far as possible and carry out the transition to the change part smoothly by the not change grating part that makes image, can further cover its existence.As a result, as shown in Figure 2 be coded image 110, wherein, watch master image easily, but be not easy to offer an explanation assistant images.As shown in Figure 3, when having with suitable direction (that is, the grating angle [alpha]) when placing coded image 110 tops, can watch assistant images (letter " SI ") with the biconvex of the corresponding line frequency of screening frequencies decoding lens 120.

By the tonal density than zonule or window of compensation master image, can further cover the existence of embedded images.This can realize by each pixel of revising in the change image, thereby makes the average tonal density of each window keep identical with the respective window that does not change image.

Those skilled in the art should be appreciated that and said method can be used with any type of point, symbol or line grating method.In addition, can use the method and other method to embed as disclosed in pending trial ' 962 and ' 943 applications, as to have the different coding parameter a plurality of assistant images.

In ' 717 patents, disclose and some similar method of said method.In the method, at first, utilization disclosed method for scrambling in ' 717 patents is encoded to assistant images, then, forms the grid stroke of master image again, to follow the pattern of the assistant images of encoding.Can use and have and master image is carried out rasterisation and encode biconvex lens (lenticular) decoding device of the identical frequency of employed frequency of assistant images is watched resulting embedded images.

If wishing output image is continuous-tone image (opposite with the grating images that is generated by first method), can use assistant images is embedded into second universal method in the master image.In the method, assistant images is embedded in " blank " contrast image that does not have other guide except regularization cycle tonal variation.Then, will have the contrast image (control image) that embeds assistant images and be mapped to master image.

Now, according to Fig. 4-6, will the simplified example of the method be discussed.Fig. 4 shows the tone value of the pixel of image wherein according to the blank image 210 that changes such as cycle functions such as square wave, sine wave, triangular waves.The frequency of the frequency of this function and biconvex lens decoding lens is complementary.The angle direction that cycle changes has formed the angle that is used for decode encoded images.As shown in Figure 5, by with assistant images in the phase place of the corresponding any position of location of content variable cycle function, assistant images 220 is embedded in the contrast image 210.According to this mode, revise the content of departing from of regularization tonal variation in the contrast image 210 corresponding to assistant images.

Then, oneself is revised contrast image 210 and arrive master image 230 by pixel mapping.The pixel of master image 230 is brightened or deepening, be complementary with pattern with the tonal variation that contrasts the respective pixel in the image 210.Final coded image has been shown among Fig. 6.Can use the transforming function transformation function that is normally defined look-up table to determine that the actual of master image pixel brightens or darken amount.These functions can be different, and this depends on image applications.For example, can design transfer function, be specifically designed to specific print processing (for example, ink-jet, dye sublimation, laser printing).

Those skilled in the art should be appreciated that and can use said method to embed a plurality of assistant images described in pending trial ' 962 applications and ' 943 applications, that have the different coding parameter.

The output of any of said method can be printed encoded image (that is, being printed on master image and hiding assistant images after the combination on document or other project), perhaps can be it is transmitted or stores the digital coding image that uses with subsequently.

The other method of embedded images is generally used for bank note and check.In the method, by change with hidden image in the corresponding position of content, visual image in the direction of raster element, create hidden image.For example, with the corresponding position of hidden image, the vertical light grid line in the master image can be changed into horizontal line.Typically, can watch hidden image by slight inclination bank note.Yet, can also utilize the optical decoder device that departing from the master image decoded.This is because in the position that does not hide content, and the grid stroke of master image will advance along the length of the lens line of demoder, still, in the position that has hidden image, will only have xsect.When watching by demoder, this species diversity make hidden image look than eyes can see much bright.

The common thinking of above-mentioned all methods and resulting coded image is: relate to and the departing from of regularization cyclophysis (for example, locus, tonal density, grating angle).Have biconvex decoding lens with the corresponding frequency of frequency of regularization characteristic by use, these are departed from become obvious.Can make the frequency of characteristic equal the lens frequency, maybe can equal the even multiple of lens frequency.Biconvex lens is used for content shielding, emphasizes and the departing from of regularization characteristic, and it is combined in the assistant images.

Can use biconvex lens to decode systematically and be embedded into coded image in master image or the background the visual coded images of its content scrambling.Yet having the use of physics (that is hardware) demoder is unrealistic or impossible situation.Therefore, the present invention proposes the method that need not to use the physical optics decoding device and the digitizing coded image is decoded.Especially, the present invention proposes and to be incorporated into the method that can be used in decoding digital coding image based on the demoder of software.The demoder of the embodiment of the invention can be suitable for decoding and comprise from unprinted digital coding image and scanned or be converted to by other device any digital coding image of the printed encoded image of digital form.Digital coding image can be the hidden image that is embedded in background or the master image, perhaps can be systematically scrambling or the visual image handled.

Now, with the method for describing according to decoded digital coded image of the present invention.Except as otherwise noted, the coded image that decode relates to master image and according to the assistant images that uses biconvex lens can watch the mode of (decoding) to embed it.Master image can be the blank image (for example, grey box) that does not have to distinguish content, perhaps can be to have the real image that can distinguish content.

Method of the present invention can be divided into two classes: (1) needs the method for the content information of master image, assistant images or master image and assistant images; And (2) do not need to know in advance the method for picture material.These two class methods all need to know the coding parameter that is used to encode and embeds assistant images.Particularly, must know line frequency and the line angle degree that is used for coded image.

Fig. 7 shows the step among the method M100 according to an embodiment of the invention, but when unmodified master image be known or the time spent, can be used for decode encoded images.This method begins at S100.At S110, obtain the digitizing copy of coded image.The digital coding image can be a version as the coded image of the direct output of automatic coding processing.Can store digital coding image, so that, perhaps it can be transferred to decoding processor from the promoter after a while by the decoding processor retrieval.Those skilled in the art should be appreciated that this type of digital coding image may never be printed on document, product, label or other can the checking project on.Because, digital form original with it provides coded image, therefore, exist to be incorporated into minimum possible distortion in the coded image, that will influence encoding process.Yet, the direction of coded image be clear and definite oneself know.

In above-mentioned replacement scheme, can be by scanning or duplicate and be printed on document, product, label or other coded image on can the checking project, obtain digital coding image.If obtain the digital coding image in this way, must take steps to guarantee the careful control (as by the direction of control document) of the relative direction of coded image with respect to scanning device, perhaps can determine the relative direction (as by bearing mark being included in) of coded image with in the coded image of permission decoding processing or near it, with the correct direction of guaranteeing that image is used to decode.

At S120, obtain to be used to produce the digital copies of the original master image of coded image.In many examples, can obtain the digitizing master image from encode processor, maybe can from the data-carrier store of when producing coded image, placing it, retrieve the digitizing master image.Alternatively, can obtain master image from the source that is used for image is provided to encode processor.At S130, rasterisation digitizing master image is to generate the contrast image.Utilization is used to produce the coding parameter of coded image and realizes this rasterisation.Especially, use comes the rasterisation master image with encode processor for producing the employed grating angle of coded image grating angle and the line frequency identical with the line frequency.In some instances, may utilize these parameters, oneself has carried out rasterisation through the copy to the master image that receives from encode processor or retrieve from data-carrier store.In the case, the master image with previous rasterisation is asserted the contrast image.

Should be appreciated that if master image just in time is the blank background image, the contrast image will with the contrast images category of Fig. 4 seemingly.Otherwise the contrast image comes down to not have assistant images to embed the variation of digital coding image wherein.

At S140, pursue pixel relatively by contrast image and digital coding image, to create difference images.Difference images can be according at whether having difference between the contrast image of each pixel and the coded image, the tone value of setting up at each pixel synthetic.For example, can distribute " very " value to the pixel that the content of coded image wherein is different from the respective pixel that contrasts image, and the respective pixel in the difference images is set to " 1 " (corresponding to white).Distribute " vacation " value to the pixel that the content of coded image wherein is identical with the respective pixel of contrast image, and the respective pixel in the difference images is set to " 0 " (corresponding to black).

Resulting difference images are to use the reconstruction with the assistant images that generates coded image with master image.Can utilize the known image Enhancement Method to strengthen the quality of difference images at the S150 place, described image enchancing method includes but not limited to: intermediate value or low-pass filter, sef-adapting filter, form are handled and client's designed image Enhancement Method.At S160, can on terminal screen, show difference images, store or print.Those skilled in the art should be appreciated that can before any enhancing step, afterwards or during show difference images.At S170, method finishes.

The quality of the coded image that using method M100 produces may be subjected to obtaining by it influence of the method for digital coding image.When coded image is that the accurate output handled of automatic coding and rasterisation master image are when using in encoding process, obtain high fidelity, when obtaining coded image originally, obtain lower a little fidelity by the digital version of carrying out digitizing or utilize image acquisition equipment to catch printed encoded image.This is that this can influence decoded result because printing and Image Acquisition (for example scanning) are handled and introduced size distortion and color harmony structural change.In addition, when comparing, coded image with respect to the deflection error of image acquisition equipment may make digital coding image not with the contrast image alignment.As mentioned above, can by careful control image acquisition process and/or by alignment keys is included in when the printed encoded image in this coded image or near, reduce these influences.

As used herein like that, term " image acquisition equipment " refers to be used for catch or produce from print image or object any equipment or the system of digital picture.Image acquisition equipment includes but not limited to: scanner, digital camera, have the system of the combination of analog camera and frame grabber.Image acquisition equipment can be suitable for utilizing the light in the visible or invisible part (for example UV and IR) of spectrum to catch image.

As mentioned above, to need master image be available to method M100.At many application, this is unpractical.Therefore, certain methods of the present invention does not have this needs.Fig. 8 show except the contrast image always outside the rasterisation blank image (for example, grating ashing box), the step of the method M200 that is used for decode encoded images same as described above.This method begins at S200.At S210, obtain the digitizing copy of coded image.In previous method, it can be original, unmodified digital coding image, perhaps can be to have printed the image of catching that obtains in the document of coded image or other project from it.At S220, set up the contrast image by utilizing with the corresponding grating angle of coding parameter and frequency, the rasterisation blank image that are used for coded image is encoded.Then, at S230, the structure difference images.Can utilize the identical pixel of in method shown in Figure 7, using of pursuing to ask difference method to construct difference images.At S240, enhancement techniques can be applied to difference images, and at S250, can display image.This method finishes at S240.

If being used to produce the master image of coded image is blank image, then the coded image that is obtained by method M200 will be just in time resulting identical with the method M100 that utilizes Fig. 7.Yet if in fact master image comprises visual information, the coded image that obtains according to method M200 will show marked difference with the decoded picture that utilizes method M100 to produce.This is because in method M100, leaches master image from master image.Then, in method M200, difference images will comprise the element of assistant images and master image.In resulting decoded picture, the assistant images of having decoded shows as and places on the master image.According to the content of these two images, this can make assistant images more be difficult to explanation or decipher.

According to the mode of the effect of simulated dual convex lens demoder more approx, developed the certain methods that is used for according to decoding digital coding image of the present invention.Biconvex lens can make the beholder watch the linear sample of the image that is obtained with the interval of being determined by the frequency of biconvex lens.These lens amplify these samples and are inserted in the continuous picture by people's vision.In the time of on being oriented in suitable angle, this causes having taking a sample with departing from of master image characteristic and amplifying of same frequency, therefore, highlights from master image.The effect of lens is that the periodic samples with coded image is combined in the reconstruction of assistant images in essence.

Fig. 9 utilizes the process flow diagram that comes the method M300 of decoded digital coded image with the similar sampling method of effect of biconvex lens.This method begins at S300.At S310, obtain the digitizing copy of coded image.As previous method, it can be original, unmodified digital coding image, perhaps can be according to the image of catching that obtains in the document of having printed coded image on it or other project.At S320, from the digital coding image, obtain a series of elongated rectangle image content sample.With be used for coded image is encoded and the directed corresponding frequency of line frequency and the coding angle that is used for coded image is encoded obtain these samples.Figure 10 and 11 shows how to obtain the picture material sample.Figure 10 shows the synoptic diagram of digital coding image 310 and single sample 322.Sample 322 has the longitudinal axis 324, is positioned at the decoding angle [alpha] place with respect to the transverse axis of coded image 310.With the corresponding frequency of frequency that is used for coded image 310 is encoded, whole coded image 310 is obtained comparable sample 322.The actual sampling that specimen width can be defined as with the biconvex lens demoder is complementary, and perhaps it can be set in advance to be less fixed width.

At S330, the combination image content sample, maintains each sample standard deviation on the identical relative position wherein with respect to other sample to form synthetic sample image.Figure 11 shows the synthetic sample image 320 that is formed by the sample 322 that obtains from coded image 310.As what can see in the illustrative examples of Figure 11, synthetic sample image has the gap between sample.At S340, expand each image pattern perpendicular to its longitudinal axis, so that the gap is near its adjacent sample.This has simulated the amplification of biconvex lens demoder.Can utilize any picture size adjustment algorithm that oneself knows in this area to realize this expansion.Resulting whole composograph provides the reconstruction of the element of assistant images and master image.At S350 and S360, can strengthen and/or show this image, as previous method.The method finishes at S370.

Similar with the method M200 of Fig. 8, method M300 does not need source images, and oneself knows in advance.Also similar with method M200, method M300 produces coded image, comprises some elements of master image.Yet the decoded result of method M300 is better than method M200 usually, because the method helps the master image element is suppressed to higher degree.

Can further improve the result of the method by according to the one or more extra composographs of additional samples set constructor that obtain with same frequency and direction (but having slightly change) with original sample.These composographs are combined the intensity of the assistant images in the decoded picture that helps further to suppress the element of master image and/or strengthen institute's perception.Can be with this process prescription: create the multilayer sample, and the different technologies (for example, use to decompose, multiply each other, average, overlapping, difference, repulsion or other general-purpose operation exclusive disjunction sequence) that utilizes known in the art being used to flatten multilayer makes up them.As the example of the value of extra composograph, as can be seen: in the specific part of coded image, the grid stroke of master image can be very thick, departs from so that stop or cover the grating that is caused by the assistant images element.Can appear local assistant images element better to obtain the second sample group from the less distance in this position.Two sample groups are averaged the general perceives that can improve assistant images.In another example, average and utilize low-pass filter that it is carried out the reconstruction that filtering can produce master image to the sample group of bigger quantity, it can be used for further suppressing master image from coded image.Should be appreciated that the quantity that does not limit sample group and operable synthetic sample image.

Method M300 has special value when the coded image that decoding is caught.Should be appreciated that image acquisition process may cause size and tonal variation, this may influence coding result.More specifically, coded image can be an alterable height with respect to the direction of image acquisition equipment.Can be by some feature being joined in the image in when coding, improve in the said method result of any.This can comprise the mark that allows identification and the distortion of orientation sum of errors in the pre-position.Can also comprise the image density standard that allows to proofread and correct tonal density.

Can also improve the execution of various coding/decoding methods by selecting the form and the content of assistant images.For example, this can relate to, and use such as black and white is square, bar code and other symbol, replaces plain text or based on the mark of image.

Should be appreciated that above-mentioned coding/decoding method and for realizing that the digital image decoding device that these methods are constructed can be suitable for any coded image that can use the biconvex lens demoder to decode is decoded.In addition, can use method of the present invention and demoder to according to (for example, visual " scrambling " image) in the independent coded image or wherein embedded the master image of hidden image or the regularization cycle in the background changes any coded image of encoding and decodes.In some embodiments of the invention, the sensitivity of coding/decoding method far surpasses the sensitivity of optical decoder device.This can change according to the indistinguishable very little cycle of optical decoder device, produced and use coded image.

As in ' 962 and ' 943 applications, discussing, a plurality of assistant images can be encoded to single coded image, each assistant images all utilizes the different coding parameter group to encode.Can use above-mentioned coding/decoding method that any amount of assistant images that is embedded in such coded image is decoded.At each assistant images, utilize its related coding parameter, simply repeat this method.

In addition, as in ' 962 and ' 943 applications, discussing, can utilize some combination results coded images of coding parameter, to be embedded in the digital document, described coding parameter can comprise that the user provides parameter, non-user to provide parameter or user to provide with non-user parameter is provided.In one embodiment, the coded image part also can be embedded into the digital document based on the information of extracting from document.After this any time, can use the software that is configured in order to carry out one of above-mentioned digital decoding method to extract/decode coded image (or a plurality of decoded picture) from digital document.Then, information in the decoded picture (or a plurality of decoded picture) and the information in the digital document can be compared, to have checked whether the document is distorted since it is protected.This relatively can manually (for example be carried out by the document user, by coded image being presented on the monitor and will carrying out visual comparison from the information and the data in the digital document of shown image) or carry out (for example, by utilize the optical characteristics identification software from decoded picture, to extract text and the suitable part of this text and digital document is complementary) automatically.

The method M400 that protects and verify digital document in this way has been shown among Figure 12.The method begins at S400, and at S410, information extraction from the digital document that will protect.This information can comprise graph image, text or other mark, and/or can comprise the explanation or the summary of the some parts of document content.Can be manually or discern and extract this information automatically.At S420, structure coding parameter group.The coding parameter group can be the user provides provides parameter with non-user combination, and can comprise the parameter that derives from the information of extracting from digital document.At S430, the assistant images that foundation will be encoded.This assistant images can be that the user provides or non-user provides.This assistant images can based on or comprise the information from digital document, extracted partly or entirely.At S440 and S450, assistant images is encoded and is embedded in the digital document.Should be appreciated that according to employed coding method, S440 and S450 can be carried out as single combination operation.In certain methods, can create coded image, and store or be transferred to the user, so that be incorporated in the digital document after a while.Should be appreciated that and to encode and be embedded in the digital document a plurality of assistant images that each such image is all encoded based on himself coding parameter group.Each of different coding image all can be provided with non-user by the user provides any combination of image and coding parameter to form.

Then, can transmit, store, print or other processing protected digital document.Any time place after coded image being incorporated in the digital document can utilize the assign to authenticity of check digit document of the proof department of method.At S460 and S470, from digital document, extract coded image and decode.Can utilize any digital decoding method that comprises said method to come decode encoded images.In a preferred embodiment, digital decoding method is incorporated in the software, automatically extracts coded image and it is decoded from digital document being used for.In a particular embodiment, can use OCR or other optical identification software to come decipher content and/or information extraction from digital document.At S480, the information of own coding image compares with the information of extracting from the digital document of just verifying in the future.If the information in the digital document of just assessing does not match with the information of collecting from coded image, can warn to the user: it is incredible existing change of digital document unauthorized or digital document.The method finishes at S495.

The verification portion that should be appreciated that method M400 can be separated with coded image generation part, can be that credible and unaltered any digital document is carried out verification operation to claiming.Can carry out different coding and decode operation, as the combination of automatic and non-automatic function.The input that it is also understood that the verification portion of method M400 is not limited to the original figure document; If document is that print, that take or other transition form, can utilize image acquisition equipment that it is carried out digitizing to produce digital document again, then, it is verified by the verification portion of method M400.

Figure 13 shows the system 400 that is used to verify digital document, is wherein carried out coding and is embedded function by encoder section 410, carries out decoding and authentication function by verification portion 430.Encoder section 410 can comprise coding module 412 and merge module 414, one of these two modules or all can communicate with encoded information database 440.Carry out adaptive or programming to coding module 412,, produce coded image so that use the coding parameter group and can comprise or the authentication image of the content that is obtained from from digital document to be extracted.Can from the addressable port module 450 that is suitable for providing the interface between user or document process module and the coded portion 410, receive this information partly or entirely.Coding module 412 can be with the coding parameter group or/and authentication image be stored in the encoded information database 440, to be used to verify digital document after a while.Coding module 412 can also be stored in coded image in the database 440 and/or with coded image and turn back to addressable port module 450.Encode processor 412 can also be provided to coded image merge module 414, and merge module 414 is suitable for coded image is embedded in the part of digital document or digital document.Then, the digital document with embedded images can be turned back to addressable port module 450.

Decoded portion 430 can comprise decoder module 432 and authentication module 434, one of these two modules or all can communicate with encoded information database 440.Decoder module 432 is suitable for retrieve encoded parameter and/or authentication image from encoded information database, and carries out digital decoding method of the present invention, to utilize the coding parameter decoding digital coding image.Decoder module 432 can also be suitable for receiving the digital document that will verify and extract coded image from this digital document.Can receive digital document from checking interface 460, described checking interface 460 is suitable as the interface between checking request unit and the verification portion 430.After decode encoded images, coding module 432 can turn back to own decoded picture verifies interface and/or incites somebody to action that decoded picture is transferred to authentication module 434.Authentication module 434 is suitable for extracting content from own decoded picture, the content of extraction and the content of validation criteria or direct extraction from digital document can be compared.Authentication module 434 can be suitable for retrieving this digital document or can be suitable for extracting it from digital document.Authentication module 434 can also be suitable for the checking result is determined and this result is turned back to the checking interface.Authentication module 434 can comprise OCR software or bar-code interpretation software, and it can be used for from decoded picture and/or digital document information extraction.

Should be appreciated that and coding module 412, merge module 414, decoder module 432, authentication module 434, encoded information database 440, addressable port module 450 and checking interface module 460 can be distributed in one or more data processors.For example, all these modules can be set on the unique user data processor.Alternatively, the different assemblies of system 400 can be assigned to by a plurality of data processors in the selective communication of network 420.

Figure 14 has described the example system 500 that is used to verify digital document, wherein, carries out various systemic-functions a plurality of on by the processor of network interconnection.In this system, on encode processor 512, carry out encoding function, and carry out decoding functions by decoding processor 532 as the part of authentication server 530 as the part of encoder server 510.Encode processor 512 can keep selective communication by the network 520 and first user processor 550.Decoding processor 532 can keep selective communication by the network 520 and second user processor 560.Encode processor 510 all keeps communicating by letter with database 540 with authentication server 530 or can selective access database 540.This visit can be via consolidated network 520 or heterogeneous networks or via another communication link.Should be appreciated that in a particular embodiment, can use predetermined regular coding/decoding parametric group, therefore, need not these parameters of storage in database 540.It is also understood that in a particular embodiment encode processor 512 and decoding processor 532 can be arranged in individual server.It is also understood that and the different schemes of Code And Decode process further can be assigned in a plurality of processors, comprise the combination and the user processor 550,560 of coding/decoding processor.In addition, user processor 550 and 560, encode processor 512 and decoding processor 532 can also be the modules of single-processor or server or the individual processors that links to each other by LAN (Local Area Network).

In typical mode of operation, wish that the user that digital document is protected submits the coded image request by first user processor 550 to encoder server 510.This request can comprise part or all of coding parameter, and can comprise the authentication image that will encode.In certain embodiments, this request can also comprise the part or all of of digital document itself.Encode processor 512 utilizes the coding parameter of the information that provides in request based on the user to small part to generate coded image.The coding parameter that is used to produce coded image can also comprise the information that non-user provides.Encode processor 512 can be stored in coding parameter and/or authentication image in the database 540, so that be used to verify digital document after a while.Encode processor 512 can also be stored in coded image in the database 540 and/or with coded image and transmit reuse family processor 550 (or another user processor), so that be embedded into digital document.Alternatively, encode processor 512 can be embedded into coded image in the part of digital document or digital document, then, this digital document is transferred to user processor 550.

Then, can print, store digital document or it is transferred to other processor, comprise second user processor 560.Can test to the authenticity of document at any time, no matter be numeral or print form.If document is a digital form, then can it be transferred to authentication server 530, to verify by user processor 560.Decoding processor 532 Receipt Validation requests are also retrieved the correlative coding parameter from database 540.Then, decoding processor 532 utilize coding parameter and digital decoding method digital coding image is decoded.Authentication server 530 can also comprise output that is suitable for handling decoding processor and the validation processor 534 that itself and the standard that is used to verify are compared.Usually, construct validation criteria in such a way: can discern changes in material or unauthorized and generate, and ignore because fidelity reduces or because the variation that the existence of master image element causes.Validation processor 534 can comprise OCR or bar-code interpretation software, and it can be used for from own decode encoded images information extraction.Validation processor 534 can also be suitable for information extraction or mark from digital document, so that compare with the information or the mark that extract from decode encoded images.

If document is printed, then can utilize the optical decoder device that has and be used to produce the coding parameter corresponding characteristic of coded image, the authenticity of document is tested.Alternatively, can utilize scanner or other image acquisition equipment 562 to catch document printing to produce the digital picture of being caught.Then, can be by user processor 560 with the Digital Image Transmission of being caught to authentication server 530, to verify.So, can utilize decoding processor 532 and validation processor 534, with the same way as of unprinted digital document, the digital picture of being caught is verified.

Should be appreciated that and to carry out by producing the document protection of coded image by some other users in document author or the document file management system.Secure documents can be stored in the database or and send to other user immediately by the Internet or Intranet (or other network).In some embodiments of the invention, be suitable for to reside on the Any user processor to the software of coded image combine digital decoding.If coding parameter can be used for this user, then this software will only can be used for decode encoded images.If the digital document recipient has decoding software and can visit coding parameter, then whether whether the recipient can use decoding software to check document have been distorted since it is protected.If the recipient prints this digital document, then document is protected by the coded image of printing with document.

Use digital decoder (that is, be applicable to the method according to this invention come any type of digital data processor of decoding digital coding image) to need not document printing so that check its authenticity or check it whether to be distorted.In addition because can be with its digital format check document, therefore, need not the optical decoder utensil have with document in the characteristic that is complementary of the coding parameter of coded image.The system of the combination of Applied Digital demoder and optical decoder device realized simultaneously with the checking to identical document of numeral and print form, therefore passed through the border that numeral arrives paper.

Digital decoder can be any data processor with the one or more software that is used to realize digital decoding method of the present invention.Digital decoder can also become or comprise the hardware realization of one or more coding/decoding methods.For example, such hardware can comprise digital signal processor (DSP) or other programmable device or be suitable for carrying out a series of nextport hardware component NextPorts of aforesaid operations sequence.

As mentioned above, digital decoder can be used for never printing electronic document or print/caught document and extracted digital coding image and it is decoded.In certain embodiments, digital decoder can also be used for extraction and decode being embedded in the coded image of hologram (hologram) and diffraction grating.

Therefore, another program of the present invention provides a kind of safer safety product of document conversion that makes from numeral to the paper form.This product can be called coded image exchange (or conversion) module.When printing the document, this security feature immediately changes the coding parameter group that is used for document protection.The coded image Switching Module is suitable for realizing exchanging the method for the coding parameter that is used for coded image.Method M500 according to an embodiment has been shown among Figure 15.This method begins at S500, at S510, receives first coded image.Utilize the first coding parameter group that this image is encoded.First coded image can be the coded image of the coded image of the new generation that directly receives from encode processor, the previous generation that from storer, retrieves or from digital document, obtain oneself extract image.In some instances, first coded image may be embedded in the digital document with the document protection at print state not, but the user wishes to change coded image before printing.

At S520, no matter its signal source utilizes digital decoder that first coded image is decoded.Then, at S530, can from decoded picture, extract the specific markers or the part of image.Then,, utilize the second coding parameter group, part or all of own decoded picture or the information extracted from decoded picture are encoded again at S540.Then, at S550, the coded image that utilizes the second coding parameter group to produce is embedded in the digital document.If from digital document, extract the original coding image, then second coded image can be returned and be embedded in the same numbers document, as the replacement of original coding image.At S560, digital document is stored and/or printed.When printing digital document, it will comprise second version of coded image.This method finishes at S595.

In certain embodiments, can be before printing digital document the S520 of encoding operation again of execute protection Enhancement Method M500 immediately.As a result, the unauthorized printing of the version previous intercepting of electronic document or suitable comprises first coded image with generation and does not comprise the copy of the document of second coded image.Therefore, the checking subsequently to unauthorised copies will appear its counterfeit essence.Can see, produce and the different phase place of transmission, the operation of method M500 repeatedly used the place that can be used to determine to usurp digital document at document.

Can make employed two coding parameter groups mutual exclusion in method M500.For example, constructing variable group in the following way: digital decoder (utilizing the first coding parameter group to operate) can not be decoded and be utilized second coded image of second parameter group coding if printed this image, and then the decode optical decoder device of second coded image (after printing digital document) of configuration can not be decoded and be utilized the first parameter group image encoded.Alternatively, can provide visit to the user of digital encoder to the first and second coding parameter groups.In the case, digital decoder can be used to first and second coded images of decoding, second coded image and the optical decoder device only limits to decode.

In the specific embodiment of protection Enhancement Method M500, first coded image can comprise the element of other safe enhancement measures, as digital watermark or bar code.For example, first coded image can comprise bar code or watermark, can utilize bar code or watermark identification and/or interpretation software and the first coding parameter group that himself is decoded.Then, can utilize the aforesaid second coding parameter group that own decoded picture is carried out the coding second time.If first coded image is formed the lens decodable picture of bar code or watermark, then can further expand this embodiment.Can utilize the first coding parameter group, first coded image of decoding, to obtain bar code or watermark, then, can utilize bar code recognition/or interpretation software and the second coding parameter group it is decoded.Then, can utilize one or more additional code parameter group that decoded information is encoded again.

The coded image exchange is created safety curtain in numeral to paper sheet document transfer point place.The user who only has a suitable coded image switch software can produce can be by the document printing of respective optical decoder examines.Suppose that the hacker invades the database of digital document, and it is downloaded and prints.Because the hacker does not have the coded image switch software, before printing, will can not encode again to coded image.Therefore, can not verify the document with the respective optical demoder.Can be set to carry out work by described barrier: if someone scans to be converted into digital format document printing according to following other modes, or utilize text edit software to create and forge document, and the coded image of being caught inserted wherein the digital decoder coded image that can not decode and be caught then.

The coded image Switching Module can also be used for delegated strategy more complicated in the document file management system.For example, all usefulness with digital decoding module can be checked the document that is in digital form per family, but the authorized user that only has the coded image Switching Module can produce the printed copies by the suitable optical decoder decode, therefore, manifest the specific copy of having printed document with suitable mandate.If before announcing digital document, it must obtain a plurality of user's approvals, if perhaps the document is unique and must only announces a copy, if perhaps each paper copy of document has monetary value, then this control hierarchy becomes and is even more important.

In the variant scheme of image exchange method, coded image can be read by digital decoder and optical decoder device, and utilize the coded image Switching Module that second coded image is encoded.This can utilize digital decoder or optical decoder device to realize detecting the tracking for the document source of counterfeit.

Should be appreciated that as using substituting of optical decoder device, can use the combination of image capture device and digital decoder.In the case, can be complementary with the coded image Switching Module is employed being used to verify that the digital decoder that catch with digitizing document printing again sets in advance to using the second coding parameter group.

In some applications, can use previously described coding method to produce multi-level coding.This can realize by own coded image being carried out encode the second time.For example, can form coded image by first assistant images and first master image.Then, this coded image as second assistant images, can be made it and is used for forming second coded image with second master image.Can utilize the different coding parameter group or even not produce second coded image with coding method.Can repeat this processing arbitrary number of times, therefore, create multi-level coding.

Hide Info if the optical decoder device is used for decoding,, will appear highest assistant images by using the demoder that is complementary with last encoding process.Then, can another demoder is placed on it, to appear from other assistant images of previous stage, by that analogy.

As using substituting of a plurality of optical decoder devices, can use digital decoder of the present invention, by using suitable coding parameter simple application and application decoder step again, the multi-level coded image of decoding.Digital decoder of the present invention is particularly useful for this purposes, because the sensitivity of its use, dirigibility and simplification.For example, in demoder, can adjust employed coding parameter easily and also can control easily, thereby can prevent from the unauthorized of specific coding image level is decoded based on software.

In the other method of multi-level coding, above-mentioned optical imagery encoding process can be combined with other image concealing or concealing method.For example, can use the digital picture that comprises digital watermarking or bar code, then, utilize one (or being used to produce other method of using the decodable image of biconvex lens) in the above-mentioned optical encoding method that this assistant images is encoded as assistant images.Alternatively, coded image can be used for digital watermarking or be embedded in the bar code image.In addition, digital decoder of the present invention can provide significant advantage for each rank of coding hierarchy is decoded.

Those skilled in the art should understand easily, and the present invention can allow the purposes and the application of broad.By the present invention and describing more than it, will be apparent except many other embodiment of the present invention as described herein and improvement project and many variants, modification and equivalent arrangements or will describe reasonably by the present invention with more than it and propose, and do not break away from the subject or scope of the present invention.

Should will not be used to protect the method for document to obscure mutually according to of the present invention with the system that is used for encrypted E-mail and digital document.Add secret emissary's unauthorized user or interceptor and can not read entire document.On the contrary, method of the present invention relates to coding and embedded images, is used to prevent to distort document but does not relate to and cover document content.Can also carry out encryption and decryption to the digital document (that is, having the document of embedding coded image wherein) that utilizes method of the present invention to protect, and not influence the protection of distorting provided by the present invention.This provides and has been used to allow the user to create the supplementary protection rank of complicated multi-stage protection system.In these system, encryption will prevent that the unauthorized during electric transmission from watching or tackle, and the use of coded image will prevent to distort document content and forgery.

Although below illustrated and described exemplary embodiments of the present invention,, be to be understood that the present invention is not limited to structure described here.Can come specific implementation the present invention with other particular form, and not break away from its spirit and essential attribute.

Claims (32)

1, a kind of method of utilizing the coded image that at least one coding parameter decodes and produced by master image and at least one assistant images, form described coded image in such a way: when printing described coded image, if do not have the optical decoder equipment with described at least one coding parameter corresponding characteristic, then the beholder can't distinguish described assistant images; Described method comprises:

Obtain the digital version of described coded image;

Determine described at least one coding parameter; And

Utilize described at least one coding parameter, make up decoded picture according to described digital coding image.

2, the method that coded image is decoded of being used for according to claim 1 is characterized in that the action that makes up decoded picture comprises:

Rasterisation contrast image has the rasterisation frequency that obtains and the rasterisation contrast image of direction with generation from described at least one coding parameter;

Each pixel of described coded image and the respective pixel in the described rasterisation contrast image are compared, to discern those coded image pixels that its content is different from the content of corresponding rasterisation contrast image pixel;

The described coded image pixel of utilizing its content to be different from the content of corresponding rasterisation contrast image pixel makes up difference images; And

Form described decoded picture according to described difference images.

3, the method that coded image is decoded of being used for according to claim 2 is characterized in that described contrast image is a blank image.

4, the method that coded image is decoded of being used for according to claim 2 is characterized in that described contrast image is the digital version of described master image.

5, the method that coded image is decoded of being used for according to claim 1 is characterized in that the action that makes up decoded picture comprises:

Obtain first group of regularization periodic samples of described coded image, obtain shape, direction and the frequency of these samples according to described at least one coding parameter;

Make up the first synthetic sample image according to described first group of regularization periodic samples; And

Expand the sample of described first group of regularization periodic samples, to fill the space between the sample and to form first decoded picture.

6, the method that coded image is decoded of being used for according to claim 5, it is characterized in that each regularization periodic samples is the elongated rectangle section with longitudinal midline axle, and the frequency of described sample is corresponding to the coding frequency that is used for coded image is encoded, and the angle direction of described longitudinal midline axle is corresponding to the coding angle that is used for coded image is encoded.

7, the method that coded image is decoded of being used for according to claim 5 is characterized in that the action that makes up decoded picture also comprises:

Obtain second group of regularization periodic samples of described coded image, except described second group of regularization periodic samples with the predetermined part in cycle between the sample, depart from described first group of regularization periodic samples, the shape of these samples, direction and frequency are identical with described first group of regularization periodic samples;

Make up the second synthetic sample image according to described regularization periodic samples; And

Expand the sample of described second group of regularization periodic samples, to fill the space between the sample and to form second decoded picture.

8, the method that coded image is decoded of being used for according to claim 7 is characterized in that the action that makes up decoded picture also comprises:

By forming described decoded picture to described first and second decoded picture applied layers leveling operation.

9, the method that coded image is decoded of being used for according to claim 8, it is characterized in that described layer leveling operation comprises implements in the following action at least one to first and second decoded pictures, and described action comprises: decompose, multiply each other, average, overlapping, ask difference and repel.

10, the method that coded image is decoded of being used for according to claim 1 is characterized in that also comprising:

Utilization is handled one or more groups that constitutes by medium filtering, low-pass filtering, adapting to image filtering and form, strengthens the quality of described coded image.

11, the method that coded image is decoded of being used for according to claim 1, the action that it is characterized in that obtaining the digital version of described coded image comprises:

The digital version of the described coded image of retrieval from data-carrier store.

12, the method that coded image is decoded of being used for according to claim 1, the action that it is characterized in that obtaining the digital version of described coded image comprises:

Receive the digital version of described coded image from encode processor.

13, the method that coded image is decoded of being used for according to claim 1, the action that it is characterized in that obtaining the digital version of described coded image comprises:

Use image acquisition equipment, catch the digital version of described coded image from the previous printing edition of described coded image.

14, the method that coded image is decoded of being used for according to claim 13, it is characterized in that described image acquisition equipment be by optical scanner, digital camera and comprise analog camera and group that the system of frame grabber constitutes in one.

15, the method that coded image is decoded of being used for according to claim 1 is characterized in that the action of determining described at least one coding parameter comprises:

Described at least one coding parameter of retrieval from described database.

16, the method that coded image is decoded of being used for according to claim 1 is characterized in that the action of determining described at least one coding parameter comprises:

Receive described at least one coding parameter from encode processor.

17, a kind ofly be used to verify wherein the method for the digital document of embedded coding image, utilized a plurality of coding parameters and the checking content extracted has made up described coded image from described digital document; Described method comprises:

From described digital document, extract described coded image;

Utilize described coding parameter, described coded image is carried out digital decoding to produce decoded picture;

From described decoded picture, extract the decoded picture content; And

Described decoded picture information and the checking content of being extracted are compared.

18, method according to claim 17 is characterized in that described checking content comprises authentication image.

19, method according to claim 17 is characterized in that described checking content comprises the document exclusive data, and described document exclusive data is unique in fact for described digital document.

20, method according to claim 17 is characterized in that described decoded picture content and the action that the checking content of being extracted compares are comprised:

Determine whether the decoded picture content of being extracted is complementary with described checking content.

21, method according to claim 17 is characterized in that described checking content is stored in the database, and described decoded picture content and the action that the checking content of being extracted compares are comprised:

The described checking content of retrieval from described database.

22, method according to claim 17 is characterized in that described decoded picture content and the action that the checking content of being extracted compares are comprised:

From described digital document, extract described checking content.

23, a kind of system that is used to verify digital document comprises:

Coding module is suitable for making up coded image to be embedded in the digital document, utilizes at least one coding parameter and the checking content extracted from described digital document makes up described coded image;

Merge module is communicated by letter with coding module, and described merge module is suitable for described coded image is embedded in the described digital document;

Encoded information database, with described coding module selective communication, described database is suitable for storing at least one coding parameter;

Decoder module, with described encoded information database selective communication, described decoder module is suitable for:

Receive described digital document,

Described at least one coding parameter of retrieval from described database,

From described digital document, extract described coded image,

Utilize described at least one coding parameter, described coded image is carried out digital decoding with the generation decoded picture, and

From described decoded picture, extract the decoded picture content;

Authentication module is communicated by letter with described decoder module, and described authentication module is suitable for described decoded picture information and the checking content of being extracted are compared.

24, system according to claim 23, it is characterized in that described system comprises user data processor, described user data processor comprises the addressable port module, described addressable port module and described coding module selective communication, and be suitable for asking coded image is embedded in the described digital document.

25, system according to claim 24, one or more groups that it is characterized in that being made of described coding module, merge module, encoded information database is the part of described user data processor.

26, system according to claim 23, it is characterized in that described system comprises authentication server, described authentication server is communicated by letter with at least one user data processor by network, described decoder module and described authentication module are the parts of described authentication server, and described authentication server is suitable for receiving confirmation of secretarial document request from described at least one user data processor, and will verify that the result turns back to described at least one user data processor.

27, a kind of method that is used to strengthen to the protection of the digital document that wherein embedded first coded image has utilized the checking content group and the first coding parameter group to make up described first coded image; Described method comprises:

Utilize the described first coding parameter group that described first coded image is carried out digital decoding to produce decoded picture;

From described decoded picture, extract described checking content group; And

Utilize the described checking content group and the second coding parameter group to make up second coded image.

28, method according to claim 27 is characterized in that described checking content comprises data unique in fact for described digital document.

29, method according to claim 27 is characterized in that also comprising:

From described digital document, extract described first coded image.

30, method according to claim 27 is characterized in that also comprising:

Described second coded image is embedded in the described digital document.

31, method according to claim 28 is characterized in that also comprising:

Printing has the described digital document of embedding described second coded image wherein.

32, method according to claim 31 is characterized in that also comprising:

But receive identifying file verifying, but described identifying file has the embedding coded image verified wherein; And

By utilizing the described second coding parameter group to attempt can verifying that coded image decodes, but identifying file is verified.

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