OA19600A - Computational method and system for image generation with coded information, images obtained therefrom and reading method and system - Google Patents

Abstract

This invention falls within the scope of steganography, i.e., encoding of information (such as a text) into other information, for example, an image. It is the object of this invention a computational method for generating at least one image with coded information comprising the steps of: i) associating an information to be coded to a plurality of graphic elements, each of the graphic elements consisting of a symbol out of a plurality of symbols, thus generating a pattern of graphic elements and ii) generating at least one image comprising at least one pattern obtained from step i). This method introduces a consistent and highly flexible way of encoding information into an image. Additionally, this invention has also as object a system associated to the said method, images obtained from the said method, as well as a reading method and system thereof.

Description

DESCRIPTION

COMPUTATIONAL METHOD AND SYSTEM FOR IMAGE GENERATION WITH CODED INFORMATION, IMAGES OBTAINED THEREFROM AND READING METHOD AND SYSTEM

THEREOF

FIELD OF THE INVENTION

This invention falls within the scope of steganography, i.e., encoding of information (such as a text) into other information, for example, an image.

BACKGROUND OF THE INVENTION

The most known method of steganography in the state-of-the-art is referred to as Least Significant Bit (LSB), wherein the least significant pixel bit of an image is used to encode information. However, when intending to retrieve this information from a printed image, one vérifiés that the LSB technique is not consistent, since both the image capture and the print bring variations in the colours and positions of the pixels, thus destroying the variation controlled by this technique.

Another methodology named as Q Art Code is also known in the state-of-the-art, wherein a région of a QR code (Quick Response code, a two-dimensional graphie code technology) is changed in order to contain a visually recognizable image. However, such a technique leads to the need to enter unnecessary information into the image, which consists of reading recognizable control patterns. There is also dependence from the image as an aesthetic and a recognizable element by a human being when generating an image according to this methodology, which is highly limiting.

The présent invention thus introduces a consistent and highly flexible way of encoding information into an image.

SUMMARY OF THE INVENTION

It is thus an object of this invention a computational method for generating at least one image with coded information comprising the steps of:

i) associating an information to be coded to a plurality of graphie éléments, each of the graphie éléments consisting of a symbol out of a plurality of symbols, thus generating a pattern of graphie éléments;

ii) generating at least one image comprising at least one pattern obtained from step i).

Such a method allows an image to be generated in a way that is dépendent on the information to be coded, thus bringing high flexibility and security, since the génération of a pattern of graphie éléments anticipâtes the génération ofthe image.

In an improved embodiment of the method of the présent invention, the génération ofthe said pattern of step i) is obtained from:

• obtaining a plurality of graphie éléments, each of them having a predefined position;

• associating the information to be encoded with the plurality of graphie éléments, thus determining the symbol of each graphie element and hence obtaining the graphie éléments pattern.

This set of steps in the génération ofthe pattern allows, in a simple and fast way, to obtain a graphie pattern, associating the information to the code. Specifically, a structure which corresponds to the set of predefined positions - is already specified, this set of positions being used, by means of association of the information to the set of symbols obtained, so as to encode the information in an obtained pattern.

In another improved embodiment ofthe method ofthe présent invention, step i) further comprises:

• obtaining at least a first pattern comprising a plurality of graphie éléments, each graphie element consisting of a first symbol out of a plurality of first symbols and • obtaining at least a second pattern comprising another plurality of graphie éléments, each other graphie element consisting of a second symbol out of a plurality of second symbols, wherein:

o the pre-defined positions of the graphie éléments ofthe first pattern are identical to the pre-defined positions ofthe graphie éléments ofthe second pattern and o the first pattern comprises the same number of graphie éléments as the second pattern.

As a conséquence, according to this improved embodiment of the image génération method ofthe présent invention, it is possible to achieve greater encoding ofthe information, thus ensuring an increased safety. Such an advantage is associated to the fact that, by obtaining at least two patterns - both of which may be appiied in the same image or in separate images - and the two patterns being related to each other by having the same number of graphie éléments and an identical set of predefined positions, it is possible to embed a certain information in a pattern and another related information into another pattern. As an example, this scheme allows one pattern to contain information encrypted with a key while the other pattern consists ofthe key.

In a preferred and advantageous configuration ofthe génération method ofthe présent invention, the step (ii) for generating at least one image comprises:

• sectioning the pattern in a plurality of cells of equal size, each cell being comprised of a number of graphie éléments constituting the pattern and • inserting each of said cells into a secondary graphie element of a plurality of secondary graphie éléments, thus obtaining a composite pattern.

This scheme is advantageous in as much as it enables the création of a graphically more complex image, separating several éléments of one same pattern through several cells that preferably contain an equal number of graphie éléments. Thus, only prior knowledge of the arrangement of the various éléments by the various cells configuring a pattern would even allow for conceiving the existence of a pattern in the resulting image. Consequently, this provides higher security in the coded information. Preferably, said insertion consists in overlapping each of the said cells to a secondary graphie element, each secondary graphie element having a size larger than each cell ofthe same size.

In yet another preferred and advantageous configuration of the génération method of the présent invention, step (ii) for generating at least one image comprises filling the entirety of a predefined area with said at least one pattern, and with a plurality of filling units consisting of a symbol from the same plurality of symbols as the graphie éléments, the symbol of each filling unit being randomly selected from the plurality of symbols. Therefore, the pattern is completely embedded in graphical éléments identical to each other, since the plurality of symbols of said filling units is the same as the graphie éléments that configure the pattern, except that these symbols (of the filling units) are randomly obtained, thus being necessarily distinct from the symbols of the graphie éléments constituting the pattern.

In another improved embodiment of the génération method of the présent invention, step ii) for generating at least one image further comprises the steps of:

• obtaining a greyscale base image and the greyscale value of each pixel of the base image;

• converting each pixel of said base image into a square cell with side K pixels, each pixel consisting of a graphie element, and each of said graphie éléments consisting of a symbol which in turn consists of a white pixel or a black pixel, the number of white or black graphie éléments in a square cell corresponding to the greyscale value of the pixel to be converted, thus obtaining a black and white converted image;

• replacing an area of the converted black and white image with the pattern obtained from step i), the said pattern comprising a plurality of graphie éléments consisting of a symbol which in turn consists of a white pixel or a black pixel;

• generating at least one image comprising the said black and white converted image.

This encoding method created on the methodology described above is based on dithering, i.e., passing an initial image - which is called a base image - from a greyscale to black and white, and thereby encoding the information by associating black and white pixels to a greyscale of one pixel of the base image. Thus, the information to be encoded becomes embedded in an image that was originally in a greyscale, thereby providing a more flexible method, which is suitable for a higher number of initial/base images.

In yet another advantageous embodiment of the method of the présent invention, the génération of at least one pattern from step i) comprises:

• obtaining at least two distinct symbols, and • obtaining a predefined number of pattern-constituting graphie éléments grouped in the same cell and consisting of one of said distinct symbols, each cell being comprised of an equal number of graphie éléments, the coded information being associated to the plurality of graphie éléments by the ratio of the distinct graphie éléments in the same cell. In this case, there is a quantization of graphie éléments, thus obtaining an additional level of coding, associating the information to be coded to a predefined number of pattern-constituting graphie éléments grouped in the same cell. In this case, preferably, the said at least two distinct base units consist of a white pixel or a black pixel, and the said value corresponding to encoded information consisting of a greyscale value, which is obtained according to the ratio of white pixels and black pixels in one same cell.

In another advantageous embodiment of the more complex génération method of the présent invention, it comprises generating a first image whose symbols consist of géométrie and complex shapes and generating a second image based on said dithering scheme whose symbols are of the pixel type, the first image containing at least one pattern whose graphie éléments hâve a predefined position identical to the predefined position of the graphie éléments of at least one pattern of the second image. This consists of a more spécifie embodiment of another one previously described, wherein two patterns in two distinct images are related to each other in that they hâve the same number of graphie éléments and an identical set of predefined positions, allowing to embed certain information in a pattern and other related information in another pattern. Alternatively, the two patterns are not related to each other, the number of graphies and/or the set of predefined positions of the first and second patterns being different. Preferably, the first image corresponds to a decryption key of information encoded in at least one pattern comprised in the second image.

In several embodiments of the method of the présent invention, the said symbols vary in colour and/or shape.

Also an object of the présent invention is an illustration with coded information comprising a first image and a second image obtained from the above described method, with a first image obtained according to the said dithering-based scheme whose symbols are of the pixel type, and a second image whose symbols consist of géométrie and complex forms.

Additionally, it is an object of the présent invention a digital image with encoded information obtained from the above described method, in any of its configurations, the said digital image being preferably rectangular.

On the other hand, an object of the présent invention is an image printed on a physical support with coded information, which is obtained from the above described method, in any of its configurations, and a subséquent step of:

• printing on physical support, the latter being preferably cellulose-based or • engraving onto a physical support, the latter being preferably metalbased, more preferably a métal alloy, or consisting of a metallised or non-metallised polyester film, optically variable, or made from a basically polymeric material, this digital image being preferably rectangular. Such a physical support may consist of a stamp, a label or a tag or any other document, such as a card, an identification card or a certificate/attestation or a postcard. Another feasible alternative is engraving/printing in money.

Additionally, it is also an object of the présent invention an illustration with coded information comprising at least one digital image as described above or at least one image on a physical support as described above, and a peripheral area, the said image being disposed within the peripheral area, not intersecting it, and preferably comprising a substantially linear contour, arranged in such a way that it séparâtes the peripheral area and the said image. Preferably, such a substantially linear contour consists of a linear sequence of white cells with black centre and black cells with white centre, yet more preferably these cells forming squares.

The présent invention further comprises another object reiated to the reading of images as disclosed above, or otherwise obtained from the génération method as described above.

It is thus an object of the présent invention a computational method for reading information encoded in an image comprising the following steps:

i) obtaining an image, which in its turn is obtained from the method for generating an image as described above;

ii) identifÿing symbols on said image;

iii) going through the symbols identified in the image in a predetermined order and comparing sets of symbols with a plurality of stored patterns.

This allows the existence of tables that match certain sets of information to symbols, that is, stored patterns to information, thus forming a dictionary.

In a preferred and advantageous mode of the reading method of the présent invention, the said obtainment of an image comprises the digital acquisition of a printed image, said printed image comprising a peripherai area, the said image with symbols being disposed within the peripherai area, not intersecting it, and comprising a substantially linear contour, arranged in such a way that it séparâtes the peripherai area and the said image. Such a configuration makes it possible to better identify the région where patterns are found and, consequently, those same patterns. Preferably, the said Symbol identification comprises identifÿing the said peripherai area and the conséquent identification of symbols within said peripherai area.

In another preferred and advantageous embodiment of the reading method of the présent invention, said identification of symbols in an obtained image further comprises a pixel repositioning step of the obtained image, the said pixel repositioning comprising:

• identifying a neighbouring set of N pixels adjacent to a first set of K x K pixels, N and K consisting of non-negative integers;

• comparing the neighbour set with an expected neighbour set, said expected neighbour set consisting of a stored pattern;

• determining the position that minimizes a norm of the différence between the neighbour set and the expected neighbour set;

• positioning of a new pixel in the position of the previous step;

• propagating the previous steps by ail the pixels of the obtained image; thus obtaining a repositioned obtained image.

This set of steps consists of a highly efficient symbol récognition methodology, unlike other methods known in the art in which there is a subdivision of an image into blocks with the same amount of pixels, quite susceptible to distortions during an image acquisition phase, such as in a photo. Preferably, this method is implemented by comparing at least a first pixel having a distinct colour from adjacent P pixels of the same colour, P consisting of a non-negative integer, with conséquent colour change from that first pixel to the colour of the adjacent P pixels, where P is preferably equal to 8.

In a preferred embodiment of the reading method of the présent invention, it comprises identifying the colour and/or the shape of symbols contained in an obtained image.

Also an object of the présent invention is a computational System for generating at least one image with coded information, comprising computational means and image génération means that are configured to implement the method for generating at least one image with coded information of this invention, in any of the configurations thereof. Preferably configured, the said means are additionally configured to generate at least one illustration and/or at least one image according to the présent invention as described above.

It is also an object of the présent invention an apparatus for reading information encoded in a computer image, which comprises computational means and preferably optical reading means, preferably consisting of a photo caméra, configured to implement the method designed for reading the information encoded in an image ofthe présent invention, in any of its described configurations.

DESCRIPTION OFTHE FIGURES

Figure 1 - représentation of an embodiment of an illustration (10) obtained from the method of the présent invention. In this case, the illustration (10) contains two images (20), each one of them comprising a pattern obtained from said method. The two images (20) may be related, in particular by the same number of graphie éléments and an identical set of pre-defined positions. The left-hand image comprises a set of pixel-like symbols (11) and the right-hand image a set of symbols (11) consisting of géométrie and complex shapes. The characteristics of the two types of symbol (11) are distinct, it being readily understood that the pixel-like symbols (11) are of smaller size (typically) and the symbols (11) consisting of complex and géométrie shapes allow for a variety of shapes.

Figure 2 - représentation of an embodiment of an image (20) obtained from the method of the présent invention. This image comprises pixel-like symbols (11) consisting of black or white pixels, an image (20) being thus obtained which represents a tree. In this image a pattern is comprised which is obtained by the method described, and which corresponds to the coded information.

Figure 3 - représentation of an embodiment of an image (20) obtained from the method of the présent invention. This image comprises symbols (11) which consist of géométrie and complex shapes, which specifically consist of triangles and squares (and which may also vary in colour), an image (20) being thus obtained which contains not only a pattern but also a set of symbols (11) randomly obtained, therefore hiding or embedding the pattern in a general image (20). Also this pattern is obtained by the disclosed method, and corresponds to the coded information.

Figure 4 - représentation of a set of patterns and images (20) obtained from the method ofthe présent invention. It should be noted that figures a) and c) are related, since they contain the same pattern, which only varies in the symbols (11) used. Figures (b) and (c) are also related because they consist of divisions of two patterns that relate to each other, with cells being thus obtained, these patterns varying only in the symbols (11) used. These divisions may be embedded in secondary graphie éléments, thus obtaining a composite pattern, as is the case of Figure d) containing the pattern of figure c), or of figure e), which comprises two cells of Figures b) and d). Figure f) represents a certain set of predefined positions in a cell constituting a pattern, and figures g) and h) represent, respectively, two patterns with distinct symbols (g) but sharing the same sequence, associated to the coded information contained in h).

Figure 5 - représentation of an embodiment of images (20) obtained from the method ofthe présent invention, the left-hand image (20) consisting of the substantially linear contour, arranged in such a manner as to separate the peripheral area (15) and said image, with the spécifie configuration of a linear sequence of white cells with black centre and black cells with white centre, these cells forming squares. In the right-hand image (20), this substantially linear contour is comprised in an illustration (10) according to the présent invention delimiting two images (20).

Figure 6 - représentation of an embodiment of part of the process for decoding the information in an image, including an acquired image (on the left, acquired via, for example, a photo caméra) and an image (20) where the substantially linear contour, in this case consisting of a rectangle, has already been identified.

DETAILED DESCRIPTION OFTHE INVENTION

The more general advantageous configurations of the présent invention are described in the Summary of the invention. These configurations are detailed below in accordance with other advantageous and/or preferred embodiments ofthe présent invention.

In one embodiment ofthe présent invention, it comprises generating a pattern, and consequently an image, through an array of graphie éléments (e.g., pixels of an image (20) or géométrie shapes of a hologram) so as to encode information without this being intelligible to a human seeing such an image. In this embodiment, the symbols (11) constituting the graphie éléments constituting the images (20) which in turn may be of two kinds: Pixel (PM) and

Shape Map (SM), i.e. the latter (SM) consist of géométrie and complex forms. Figure 1 illustrâtes these two types of visual éléments. On the left, the représentation of a tree is based on symbols (11) of PM type (composed only by black and white pixels, although when viewed from a distance we hâve the sensation that there are pixels of other shades of grey); while the représentation on the right, consisting of triangles and squares, is ofthe SM type.

A PM-based image (20) may consist of a digital image (20) created with a suitabie résolution for the printing technique to be used, as well as the ability of a common photo caméra to recognize such pixels from a photograph of such image printing. An SM-based image (20) may consist of an image (20) composed of small géométrie shapes or small drawings. The said image (20) may normally be printed (for example, using a laser printer on a paper, offset), or printed on other materials (for example, a security hologram generated by électron beam lithography).

A pattern consists of an array of graphie éléments that comprise an image (20) or visual element, or at least part of that image. In one embodiment, the position ofthe éléments is defined from a reading-and-writing structure, which détermines the position of the graphie éléments. A pattern comprises graphie éléments which in turn consist of symbols (11) out of a plurality of symbols (11), and such association is stored in what may be referred to as a dictionary. Once the dictionary is defined, it is possible to create a pattern and thus a visual element with a coded message, as well as décodé a message contained in an image.

A pattern is composed of graphical éléments which may consist of symbols (11) out of a plurality of symbols (11). For example, the symbols (11) of a black and white image (20) consist of a black pixel and a white pixel. In addition to the symbols (11), it is necessary to define a structure of predefined positions of the graphie éléments corresponding to symbols (11). This structure defines the position of each graphie element. Once the positions hâve been defined, it is possible to obtain several patterns.

Figure 4 shows two patterns among which only the symbols (11) corresponding to the graphie éléments vary. The image 4a shows a visual element composed of symbols (11) ofthe SM type. The graphie éléments are divided into sets of 4 units, as highlighted in figure 4b (cells). Similarly, the images 4c and 4d show patterns composed of black and white pixels, as well as their division into cells, according to an embodiment of the présent invention. Such images (20) contain 4 cells, each one of them with 4 graphie éléments. Ail cells conform to a pattern, that is, a spécifie distribution of the graphie éléments. The cells highlighted in image 4e 5 were created using the structure shown in image 4f. In this way, the éléments of a cell are interpreted sequentially, as shown in image 4g. Finally, in this embodiment each graphie element is associated to an index (the position of the graphie éléments, in sequence). Therefore, this graphie sequence can be interpreted abstractly as a numerical sequence. In this example, black pixels and triangles are associated to index 0, while white pixels and squares are 10 associated to index 1. This numerical sequence allows a dictionary to be defined.

In one embodiment, it is possible to represent a dictionary in a more generic way by replacing the pattern applied to a set of symbols (11) with a sequence of indexes. Accordingly, a same dictionary can be used to encode and décodé information in patterns 15 generated with graphie éléments to which distinct symbols (11) correspond (with the restriction that the two patterns contain an equal number of graphie éléments).

In one embodiment, the pattern contains a distribution of graphie éléments to which a given quantum value can be associated. For example, in a 2x2 pattern formed by two 20 graphie éléments, to which two distinct symbols (11) correspond, we can hâve the following configurations:

Amount of	Amount of	Quantum
symbol 1	symbol 2
0	4	0
1	3	1
2	2	2
3	1	3
4	0	4

From the quantization of a base image (20) we can establish a relation between a pattern and a quantum. For instance, in the examples, considering graphie éléments corresponding to black (symbol (11) 1) and white (symbol (11) 2) pixels, it is possible to quantize a grey scale image (20) in five grey tones (0, 64, 127, 192, 255). Each tone can be associated with a spécifie quantum. In this way, it is possible to start from a greyscale image (20), quantizing that image (20) and encoding a message at the positions associated to the pixels/symbols (11) whose colour is associated to the quantum used in a dictionary.

In an embodiment ofthe decoding method ofthe présent invention, it comprises the step of going through an image obtained (e.g., by a photo caméra) in a spécifie order by looking for sets of graphie éléments defining a pattern in a dictionary, this dictionary being stored. Once the said pattern has been identified, it is possible to identify a message associated with it by referring to said dictionary.

For the purposes of the présent embodiment, it is considered that the image (20) to be decoded is printed. Thus, in a first step, a photograph of this image (20) must be captured and then one or more existing patterns therein shall be obtained in order to perform a decoding process.

In this embodiment, and as regards the image acquisition details, raw data captured by a photo caméra are used.

From these raw data, a rectangular image (20) is obtained whose resolution is an integer multiple of the resolution of a possible image, obtained according to this invention, contained in the captured photograph. Since the images (20) may hâve different aspect ratios according to the symbols (11) / graphie units / patterns therein - it is necessary to identify a layout from that photograph.

To that end, in this embodiment, the said substantially linear contour is used, in the présent embodiment consisting of an edge around the image (20) that can be efficiently identified. This can be implemented by searching for contours in the captured image (20). Among the contours found, a contour is selected that is well approached by a quadrilatéral and whose area is preferably proportional to the resolution ofthe photograph. Then, a homography is estimated from the vertices of this rectangle. From this homography, it is possible to apply a warping or rectification on the photograph and, finally, to make a eut based on the identified rectangle. This process results in an image (20) that may be larger than the visual identity, but its dimensions keep the said aspect ratio.

Figure 6 shows on the left side a photographie image (20) which contains an image obtained according to the method of the présent invention, with two patterns. This image (20) comprises an edge such as the one in the left image (20) of Figure 5. On the right, an image (20) is shown which results from the edge identification process ofthe above-described embodiment.

The edge ofthe image (20) of Figure 6 contains a continuous black rectangular contour which is positioned in the outermost portion. This contour consists of two sets of 3x3 graphie éléments, these graphie éléments consisting of symbols (11) which in turn consist of white or black pixels (a set with the 8 external graphie éléments consisting of black pixels, and the internai of white pixels or vice versa). The method ofthe above-described embodiment is based on the edge, i.e. on the outer continuous contour.

The approach of this embodiment of the decoding method of the présent invention comprises repositioning the samples of the pixels passing through the centre of the patterns of said edge. For each of these pixels, a set of neighbouring KxK pixels is tested and a neighbourhood is compared around this neighbour set with the expected neighbourhood (since the edge pattern is known). The position ofthe pixel that minimizes the norm ofthe différence between neighbourhoods will be the new position ofthe respective sample.

This repositioning is propagated to the pixels within the image (20) by an interpolation process. The horizontal variations of the upper and lower edges will be interpolated to correct the abscissae of the samples, while the vertical variations of the right and left edges will be used to correct the ordinates ofthe samples.

In addition to said overall repositioning performed from the edge repositioning of this embodiment, a local repositioning approach is also implemented. This approach is accomplished by identifying isolated points along the image (20) with coded information. These points are either black pixels in which the closest 8 neighbours are white, or white pixels whose closest 8 neighbours are black (similar to those used at the edge). Among ail detected contours, the chosen ones are those which satisfy a rule based on pre-defined diameter and occupied area.

In this embodiment, the most direct approach for recognizing the colour of a pixel is to use a predefined threshold. Thus, after determining the position of the sample, the colour of the respective pixel will be black if the sample's grey level is less than the threshold, otherwise the colour ofthe pixel will be white.

In this embodiment, after identifying the area containing the image (20) with encoded information, a search and identification of shapes contained therein, i.e., the graphie éléments, is initiated. These may consist of symbols (11) which are basic shapes (such as squares, triangles, circles, etc.) or more complex and elaborate shapes (such as blazons, shields, etc.).

In the case of simple shapes, a segmentation ofthe area ofthe acquired image (20) is performed into sections and with the aid of a contour detector the graphie unit in the section is identified and recorded.

In the case of more complex shapes, the same process is used, associated to a detector and descriptor of characteristics. Each graphie element must hâve a unique set of characteristics, enablingthe identification of which one is présent in each field ofthe cell. Such identification may be carried out by any means known in the State ofthe art.

Said caméra consists of any type of equipment capable of capturing images, which may include a mobile phone or a scanner.

As will be évident to the person skilled in the art, this invention should not be limited to the embodiments described herein, and a number of changes are possible which remain within the scope ofthe présent invention.

Obviously, the different configurations and embodiments shown above are combinable, in the different possible forms, the répétition of ail such combinations being herein avoided.

Claims (24)

1. A computational method for generating at least one image (20) with coded information characterized in that it comprises the steps of:

5 i) associating an information to be encoded with a plurality of graphie éléments, each of the graphie éléments consisting of a symbol (11) out of a plurality of symbols (11), thus generating a pattern of graphie éléments;

ii) generating at least one image (20) comprising at least one pattern obtained from step i); and wherein

10 the symbols (11) constitute the graphie éléments and the graphie éléments constitute the images (20); and wherein the symbols (11) consist of two kinds selected from Pixel (PM) and/or Shape Map (SM), wherein the Shape Map (SM) consist of géométrie and complex forms.

2. The computational method for generating at least one image (20) with coded information according to the previous claim, characterized in that the génération of the said pattern from step i) comprises:

• obtaining a plurality of graphie éléments, each one having a predefined position;

20 · associating the information to be encoded to the plurality of graphie éléments, thus determining the symbol (11) of each graphie element and thereby obtaining the graphie element pattern.

3. The computational method for generating at least one image (20) with

25 coded information according to the previous claim, characterized in that step i) further comprises:

• obtaining at least a first pattern comprising a plurality of graphie éléments, each graphie element consisting of a first symbol (11) out of a plurality of first symbols (11) and

30 · obtaining at least a second pattern comprising another plurality of graphie éléments, each other graphie element consisting of a second symbol (11) out of a plurality of second symbols (11), wherein:

o the pre-defined positions of the graphie éléments of the first pattern are identical to the pre-defined positions of the graphie éléments of the second pattern and

5 o the first pattern comprises the same number of graphie éléments as the second pattern.

4. The computational method for generating at least one image (20) with coded information according to any one of the previous claims, characterized in that the step ii) 10 for generating at least one image, comprises:

• sectioning the pattern in a plurality of cells of equal size, each cell being comprised of a number of graphie éléments constituting the pattern and • inserting each of said cells into a secondary graphie element of a plurality of secondary graphie éléments, thus obtaining a composite pattern.

5. The computational method for generating at least one image (20) with coded information according to the previous claim, characterized in that said insertion consists of overlapping each of the said cells to a secondary graphie element, each secondary graphie element having a size larger than each cell of the same size.

6. The computational method for generating at least one image (20) with coded information according to any of the previous claims, characterized in that the step ii) for generating at least one image comprises filling the entirety of a predefined area with said at least one pattern, and with a plurality of filling units consisting of a symbol (11) from the same 25 plurality of symbols (11) as the graphie éléments, the symbol (11) of each filling unit being randomly selected from the plurality of symbols (11).

7. The computational method for generating at least one image (20) with coded information according to any of the claims 1-3, characterized in that the step ii) for 30 generating at least one image further comprises the steps of: — • obtaining a greyscale base image (20) and the greyscale value of each pixel of the base image (20);

• converting each pixel of said base image (20) into a square cell with side K pixels, each pixel consisting of a graphie element, and each of said graphie éléments consisting of a symbol (11), which in turn consists of a white pixel or a black pixel, the number of white or black graphie éléments in a square cell corresponding to the greyscale value of the pixel to be converted, thus obtaining a black and white converted image;

• replacing an area of the converted black and white image with the pattern obtained from step i), the said pattern comprising a plurality of graphie éléments consisting of a symbol (11), which in turn consists of a white pixel or a black pixel;

• generating at least one image (20) comprising the said black and white converted image.

8. The computational method for generating at least one image (20) with coded information according to any of the daims 2-7 characterized in that the génération of at least one pattern from step i) comprises:

• obtaining at least two distinct symbols (11), and • obtaining a predefined number of pattern-constituting graphie éléments grouped in one same cell and consisting of one of said distinct symbols (11), each cell being comprised of an equal number of graphie éléments, the coded information being associated to the plurality of graphie éléments by the ratio of the distinct graphie éléments in one same cell.

9. The computational method for generating at least one image (20) with coded information according to the previous claim, characterized in that the said at least two distinct base units consist of a white pixel or a black pixel, and the said value corresponding to encoded information consisting of a greyscale value, which is obtained according to the ratio of white pixels and black pixels in one same cell.

10. The computational method for generating at least one image (20) with coded information according to any of the previous daims, characterized in that it comprises generating a first image (20) from any of the daims 1-6 whose symbols (11) consist of géométrie and complex shapes and generating a second image (20) from claim 7 whose symbols (11) are of the pixel type, the first image (20) containing at least one pattern whose graphie éléments hâve a predefined position which is identical to the predefined position of the graphie éléments of at least one pattern of the second image (20).

11. The computational method for generating at least one image (20) with coded information according to the previous claim, characterized in that the first image (20) corresponds to a decryption key of information encoded in at least one pattern comprised in the second image (20).

12. The computational method for generating at least one image (20) with coded information according to any of the previous claims, characterized in that the said symbols (11) vary in colour and/or shape.

13. An illustration (10) with coded information, characterized in that it comprises a first image (20) and a second image (20) obtained from the computational method for generating at least one image (20) with coded information according to any of the claims 11-12.

14. A digital image (20) with coded information, characterized in that it is obtained from the computational method for generating at least one image (20) with coded information of any of the claims 1-12, the said image being preferably rectangular.

15. An image printed on a physical support with coded information, characterized in that it is obtained from the computational method for generating at least one image (20) with coded information according to any of the claims 1-12 and from a subséquent step of:

• printing on physical support, the latter being preferably cellulose-based or • engraving onto a physical support, the latter being preferably metal-based, more preferably a métal alloy, or consisting of a metallised or non-metalljsed polyester film, optically variable, or made from a basically polymeric material, this digital image being preferably rectangular.

16. An illustration (10) with coded information, characterized in that it comprises at least one digital image (20) with coded information from claim 14 or at least one image printed on a physical support with coded information from claim 15, and a peripheral area (15), the said image (20) being disposed within the peripheral area (15), not intersecting it, and preferably comprising a substantially linear reference, arranged in such a way that it séparâtes the peripheral area (15) and the said image.

17. A computational method for reading information encoded in an image (20) characterized in that it comprises the following steps:

i) obtaining an image, which in its turn is obtained from the computational method for generating at least one image (20) with coded information according to any of claims 1-12;

ii) identifying symbols (11) on said image;

iii) going through the symbols (11) identified in the image in a predetermined order and comparing sets of symbols (11) with a plurality of stored patterns.

18. The computational method for reading information encoded in an image (20) according to the previous claim, characterized in that the obtainment of an image (20) comprises the digital acquisition of a printed image, the latter comprising a peripheral area (15), the said image (20) with symbols (11) being disposed within the peripheral area (15), not intersecting it, and comprising a substantially linear contour, arranged in such a way that it séparâtes the peripheral area (15) and the said image.

19. The computational method for reading information encoded in an image (20) according to the previous claim, characterized in that the identification of symbols (11) comprises identifying the said peripheral area (15) and the conséquent identification of symbols (11) within said peripheral area (15).

20. The computational method for reading information encoded in an image (20) according to any of the claims 18-19, characterized in that the said identification of symbols (11) in an obtained image further comprises a pixel repositioning step ofthe obtained image, the said pixel repositioning comprising:

• identifying a neighbouring set of N pixels adjacent to a first set of K x K pixels, N and K consisting of non-negative integers;

• comparing the neighbour set with an expected neighbour set, the said expected neighbour set consisting of a stored pattern;

• determining the position that minimizes a norm ofthe différence between the neighbour set and the expected neighbour set;

• positioning of a new pixel in the position ofthe previous step;

• propagating the previous steps by ail the pixels of the obtained image; thus obtaining a repositioned obtained image.

21. The computational method for reading information encoded in an image (20)according to the previous claim, characterized in that it is implemented by comparing at least a first pixel having a distinct colour from adjacent P pixels ofthe same colour, P consisting of a non-negative integer, and with a conséquent colour change from that first pixel to the colour ofthe adjacent P pixels, where P is preferably equal to 8.

22. The computational method for reading information encoded in an image (20) according to any ofthe previous claims, characterized in that it comprises identifying the colour and/or the shape of symbols (11) contained in an obtained image.

23. A computational system for generating at least one image (20) with coded information, characterized in that it comprises computational means and image (20) génération means that are configured to implement the computational method for generating at least one image (20) with coded information according to any of the claims 1-12, being preferably configured to generate at least one illustration (10) with coded information according to claim 13 and/or at least one digital image (20) with coded information according to claim 14 and/or at least one image printed on a physical support with coded information according to claim 15 and/or at least one illustration (10) with coded information according to claim 16.

24. A computational apparatus for reading information encoded in an image (20) characterized in that it comprises computational means and, preferably, optical reading means, which preferably consist of a photo caméra, configured to implement the computational method for reading information encoded in an image (20) according to any of the claims 17-22.