WO2018109421A1

WO2018109421A1 - Method of measuring a part of the body using digital photographs, and implementation of such a method for manufacturing customized shoes

Info

Publication number: WO2018109421A1
Application number: PCT/FR2017/053623
Authority: WO
Inventors: Maxime MOREAUD; Franck LE FRANC; Sophie ENGSTER; Frédéric ITTHIRAD
Original assignee: Chamberlan
Priority date: 2016-12-15
Filing date: 2017-12-15
Publication date: 2018-06-21
Also published as: EA201991588A1; FR3060735A1; EP3555559A1; FR3060735B1

Abstract

The invention relates to a digital photogrammetry method for measuring a part of the human body, preferably a foot, or a hand or a neck, without 3D reconstruction of said body part. In particular, the invention allows characteristic dimensions of a foot to be determined using digital images, in order to use them to manufacture customized shoes. The photographs are advantageously taken using a smartphone comprising a camera, by the person himself or herself, according to a simple image-shooting procedure.

Description

METHOD FOR MEASURING A PART OF THE BODY FROM DIGITAL PHOTOGRAPHS, AND IMPLEMENTING SUCH A METHOD FOR THE MANUFACTURE OF

CUSTOM SHOES

Field of the invention

The present application relates to the field of measurement from digital photographs, also called photogrammetry, in particular the measurement of a part of the human body, and more specifically the measurement of a foot. The invention is advantageously used in the context of the manufacture of tailor-made shoes.

General context and objectives of the invention

Measurement methods are known from digital images of an object, in particular the human body, using complex image processing procedures to provide a three-dimensional (3D) reconstruction of the object.

Numerous methods for 3D reconstruction of an object from digital photographs exist, some based on the use of a calibration chart for the sensor calibration step, and on the processing of several images of the object. for the reconstruction of it in space.

The present invention provides a simple and robust method for measuring a body part, such as a foot, hand or neck, from digital photographs, without using a 3D reconstruction of said body part. The proposed method can advantageously be implemented by the person himself who wishes to measure a part of his body, without a dedicated imaging device, that is to say for example by means of a simple smart phone comprising a camera.

The present invention aims in particular to provide measurements made according to this method for the custom-made manufacture of a shoe, in the case where a foot is measured, or a fashion accessory, typically a jewel, to from the measurement of the foot or other part of the body such as the hands or the neck of a person.

The invention makes it possible, in particular, to estimate only the characteristic dimensions of the part of the body which one wishes to measure which will be useful for the custom-made manufacture. Summary of the invention

The invention thus relates more specifically to a method of measuring a part of the human body from digital photographs, without 3D reconstruction of the body part, comprising the following steps:

the acquisition by means of a device for photographic acquisition of at least one photograph of the part of the body and of a known 2D pattern comprising at least three markers, so that the photograph contains at least one characteristic dimension of the part of the body that one wishes to determine and the three markers of the test pattern;

calibrating the photographic acquisition device from said at least one photograph and the at least three markers of the known 2D pattern, by establishing a calibration matrix allowing the correspondence between a point of the photograph and a point 3D expressed in a world landmark;

determining the characteristic dimension of the body part from said at least one photograph and the calibration matrix.

Preferably, the characteristic dimension of the body part is a Euclidean distance between two points of the body part or a perimeter of the body part.

According to one implementation, at least one characteristic dimension of the part of the body is determined from a single photograph and the calibration matrix, the matrix making it possible to carry out the correspondence between a point of the photograph and a 3D point situated in the plane of the sights and expressed in the world landmark.

According to one implementation, at least two photographs are acquired with the photographic acquisition device in two different positions so that each photograph contains said at least one characteristic dimension to be determined, it is estimated the transformation between the positions of the two photographs during of the calibration, and determining said at least one characteristic dimension knowing said transformation.

According to one implementation, at least one Euclidean distance characteristic dimension is determined between two points from two photographs, said two photographs being acquired in a translational movement of the photographic acquisition device.

According to one embodiment, at least one perimeter-type characteristic dimension is determined from n photographs taken in n different positions around the part of the body, n being greater than or equal to two, typically between 3 and 10 photographs. In this case, the length of the apparent diameter di in photograph i is preferably measured on each photograph i, i ranging from 1 to n, and the perimeter p is estimated by the following formula:

P = -Σ ^d i

n i = i

Advantageously, the photographic acquisition device is a camera of a smart phone.

According to one implementation, the photographs are transmitted to a remote computer to perform the steps of calibration and determination of the characteristic dimension (s) of the body.

According to one implementation, the following steps are performed:

- we express the plane formed by the 2D chart in the world landmark;

the at least one photograph is superimposed on a generic 3D model of the part of the body to be measured, the model being previously calibrated with real generic dimensions of the part of the body to be measured, and;

the 3D model is deformed on the photograph in order to coincide the characteristic points belonging to the plane formed by the 2D pattern of the photograph and the model

3D;

the characteristic dimension is determined from the deformed 3D model.

According to one implementation, the acquisition of the photographs is guided by means of visual indications, such as the transparency display in the photograph of a drawing of the part of the body and the sight, or by means of indications. sound such as a beep or tactile indications such as vibrations preferably signaling that the gesture made for the acquisition is not the right one.

According to one embodiment, a foot is measured, and the characteristic dimension of the measured foot is a characteristic dimension useful for a box, preferably chosen from a length, a width, a height, a perimeter of a part of the foot.

Preferably, at least one characteristic dimension of at least one measuring point of the following foot is determined:

- the shoe size ;

- the size of the fingers;

- the instep;

- the entrance

- malleolus;

- ankle ;

- the strong point of the calf; - the knee; and

- the little toe-heel,

and at least one characteristic dimension is preferably determined for each of said measuring points.

According to one implementation, at least two photographs are acquired during at least one of the following movements (a) to (d):

(a) a translational movement of the photographic acquisition device above the foot, preferably in a substantially horizontal plane and in a direction perpendicular to the length of the foot;

(b) a translation movement of the photographic acquisition device inside and outside the foot, preferably in a substantially vertical plane and in a direction parallel to the length of the foot;

(c) a rotational movement of the photographic acquisition device around the ankle;

(d) a rotational movement of the photographic acquisition device around the leg, and determining at least one of the characteristic dimensions of the following measurement points according to the movements of the photographic acquisition device during the acquisition of the photographs:

- the size at the fingers and / or the instep from the photographs acquired according to the movement (a);

- the size and / or the size of the fingers and / or the instep and / or the entrance and / or the malleolus from the photographs acquired according to the movement (b);

- the entrance and / or ankle from the images acquired according to the movement (c);

- the strong point of the calf and / or the under knee and / or the small toe-heel from the photographs acquired according to the movement (d).

According to one implementation, a hand or a neck is measured.

According to a second aspect, the present invention relates to a method of manufacturing a shoe, in which:

at least one characteristic dimension of the foot is determined by the measuring method according to the invention, preferably at least the size, and even more preferably the characteristic dimensions of all the following measuring points: the size, the size at the fingers, the instep, the entrance, the malleolus, the ankle, the strong point of the calf, the under-knee, and the little toe-heel; and

a tailor-made shoe is produced from said at least one characteristic dimension of the foot, and preferably from the characteristic dimensions of all said measurement points. According to a third aspect, the present invention relates to a method of manufacturing a fashion accessory adapted to the morphology of a part of the human body, wherein: at least one characteristic dimension of the part of the body, preferably of a hand, a neck or a foot, is determined by the method according to the invention, and preferably the diameter of a finger of the hand, the diameter of the wrist, the diameter of the neck, or the diameter of a part of the foot such as the ankle; and

said custom mode accessory is made from said at least one characteristic dimension.

Other objects and advantages of the invention will appear on reading the following description of examples of particular embodiments of the invention, given by way of non-limiting examples, the description being made with reference to the appended figures described herein. -after.

Brief description of the figures

FIG. 1A illustrates an exemplary implementation of the measurement method according to the invention comprising taking a photograph (s) with a smartphone of a human foot placed on a staff.

Figure 1B is an example of a 2D pattern used for calibrating the photographic acquisition device.

FIGS. 2A and 2B illustrate an implementation of the invention in which a length such as the length of a foot (size) is determined by means of a 2D pattern and a photograph. Figure 2A is a diagram of the shooting of the foot and the sight. FIG. 2B represents the photograph acquired during the shooting according to FIG. 2A.

FIGS. 3A and 3B illustrate an implementation of the invention in which a length such as the length of a foot (size) is determined by means of a 2D pattern and two photographs. Figure 3A is a diagram of the shooting of the foot and the sight. FIG. 3B represents two photographs acquired during the shooting according to FIG. 3A.

FIGS. 4A and 4B illustrate an implementation of the invention in which a perimeter of the foot, in particular the perimeter of the instep, is determined by means of a 2D pattern and three photographs. Figure 4A is a diagram of the shooting of the foot and the sight. FIG. 4B represents the three photographs acquired during the shooting according to FIG. 4A. FIG. 5 illustrates the different measurement points of a foot that can be determined by the method according to the invention.

Figure 6 illustrates the gesture made for the acquisition of the images according to an implementation of the invention.

In the figures, the same references designate identical or similar elements. Detailed description of the invention

The present invention relates to a method for measuring a portion of the human body from digital photographs using a digital photographic acquisition device, a test pattern and a specific algorithmic processing of the acquired photographs.

Advantageously, the measurement according to the invention does not rely on a 3D reconstruction of the part of the body, as may be the case with known methods. Such a 3D reconstruction of an object mainly means that the whole object of study is reconstructed, that is to say that a 3D representation of the object is obtained from a set of images of the object taken from different angles of view. By 3D reconstruction of an object from digital photographs, we mean a 3D digital reconstruction of the object, that is to say a 3D digital model reproducing the same or almost the real object. It is therefore conceivable that from this 3D reconstruction one could estimate any dimension that one would like to know about the object of study. However, the 3D reconstruction of an object generally makes use of complex procedures for acquiring and processing images, which are often expensive in terms of computation time. This approach by 3D reconstruction of the object has not been adopted by the inventors.

The present invention thus proposes a method of measuring a part of the human body from digital photographs, without 3D reconstruction of said part of the body, which allows the estimation of characteristic dimensions of said body part.

The method comprises the following steps:

the acquisition by means of a device for photographic acquisition of at least one photograph of the part of the body and of a known 2D pattern comprising at least three markers, so that the photograph contains at least a characteristic dimension of the part of the body that one wishes to determine and the three markers of the test pattern;

calibrating the photographic acquisition device from said at least one photograph by establishing a calibration matrix allowing the correspondence between a point of the photograph and a 3D point expressed in a world coordinate system;

determining the characteristic dimension of the part of the body from the said at least one photograph and the calibration matrix.

In particular, because the method according to the invention does not rely on a 3D reconstruction of said part of the body, but also because of the flexibility of shooting implemented and the type of image processing performed, detailed below in the description, the present method is simple and robust.

Several parts of the human body such as the feet, the hands or the neck can thus be measured with the method according to the invention. In particular, the present invention relates to a method of measuring a foot, allowing the determination of foot characteristic dimensions useful to a box for the manufacture of custom shoes.

In the following description, the method according to the invention is described in the case of measuring a foot.

Beforehand, certain terms used in the present description are hereinafter specified.

The term foot in the present description is understood to encompass the foot as such, and part of the leg up to the knee. The term included here all the parts of the foot and the leg whose measure is useful to a shoemaker.

Similarly, the term hand used in the present description encompasses the hand as such as well as the wrist, or even the part of the arm up to the elbow. It refers to all the parts of the hand and arm whose measurement is useful in the manufacture of a jewel type fashion accessory, for example a ring or a bracelet.

In the present description, the term smartphone, taken from English terminology, is used to designate a smartphone, which conventionally comprises a camera.

By photography is meant an image obtained by a photographic process, that is to say obtained by the action of light on a sensitive surface. The term image in the present description will also be used to designate a photograph. The present invention relates exclusively to the use of digital photographs.

By world reference means an orthonormal reference reference associated with the real three-dimensional space where the object of study is located, that is to say the part of the body that one wishes to measure. We can note this reference R ₀ , of origin 0: (? ₀ , AO, Y ₀ , Z _Q.

Figure 1A schematically illustrates a shooting of the method according to the invention. A foot 10 is placed on a two-dimensional (2D) pattern 30 bearing identifiable markers 40.

The shooting is for example carried out by means of a smartphone 20, conventionally comprising a camera. The use of such a non-dedicated and widespread image acquisition device is advantageous. In addition, the use of a smartphone allows easy shooting, freehand, can be performed by the person himself who seeks to measure a part of his body, or possibly by a third person.

The photographic sensor of the smartphone can be used in both photography mode and video mode, provided that the quality of the images and resolution allows it. In video mode, it exploits part of the images acquired by the sensor. The target 30 is placed so as to be visible by the image acquisition device, just like the foot 10 to be imaged. The target 30 may be placed under or next to the foot to be imaged.

At least one image of the foot 10 and the target 30 is acquired by the smartphone 20, so that the image contains all or the characteristic dimensions of the foot 10 that one wishes to determine, and at least three markers 40 of the test 30.

The target 30 serves to calibrate the image acquisition device. This calibration pattern includes reference elements of known geometry. Thus, the target 30 has at least three markers 40 which form patterns that can be identified in the image, for example black dots on a white background or vice versa, or any other identifiable pattern, preferably capable of being detected automatically. in the picture. An example of a pattern 30 is shown in Figure 1B. This is a simple sheet of A4 paper with identifiable markers 40 at the four corners of the sheet, referenced 1 to 4 in Figure 1B. The standardized dimensions of such a sheet are known. The markers can be placed differently on the sheet, as long as we know the distance between them and / or their size.

The 2D pattern 30 is known, that is to say that geometric information is available on the markers 40 (at least three) of the pattern, typically the distance between the markers 40 and / or the size of the markers, and allows the calculation of the position of the image acquisition device in the space, expressed in the world reference. This calibration step of the image acquisition device then makes it possible to determine the characteristic dimensions of the object studied, e.g. the foot, from the points in the image, that is to say allows a calibrated measurement. This type of calibration is known, and for example described in the book "Multiple View Geometry in Computer Vision" by Richard Hartley and Andrew Zisserman (Part I: Geometry and Single View Geometry Camera, Cambridge University Press, pp. 151-233). , 2004). The calibration of the image acquisition device consists in establishing, from at least one photograph taken as described above, and from and markers of the 2D pattern, a calibration matrix allowing the correspondence between a point of the image and a 3D point expressed in a world landmark.

For each acquired image, the positions in the image of at least three markers 40 of the target 30 are extracted. This extraction can be performed manually: an operator points with a pointing device, such as a mouse, or a finger or a conductive tip if a touch on a touch screen is used, the positions of markers 40. This extraction can also be performed automatically with certain image processing techniques, as for example described in Lowe, 1999 ("Object recognition from local scale-invariant features", Proceedings of the International Conference on Computer Vision , vol 2, 1999). Preferably, the automatic extraction is based on a technique as described in Lowe 1999, having the particularity to be able to match a pattern representing the marker without being sensitive to projective geometric transformations. Once these positions are extracted, it is possible to calculate a calibration matrix, as described for example in Hartley and Zisserman, 2004 ("Multiple View Geometry in Computer Vision", 2004, Part I "Geometry and Single View Geometry Camera" and Part II "Two-View Geometry", Cambridge University Press, pp. 151-233 and pp. 237-308), for mapping the positions of the points in the image to the 3D positions of the points in the plane. of the target 30 in the world landmark. Real distance measurements between two points are then feasible, as illustrated in FIGS. 2A / B, 3A / B, 4A / B described below.

Thus, once the calibration is performed, it is possible to determine the characteristic dimension of the foot from the calibration matrix and at least one image.

The method according to the invention makes it possible in particular to determine a length of a part of the body, that is to say a Euclidean distance between two points of a part of the body. It can be the length, the width or the height of a part of the body, according to the usual definition of these dimensions (length: distance between the two ends furthest from an object / width: dimension perpendicular to the length / height: dimension in the vertical direction, from the base to the top of an object). The measured characteristic dimension may also be a perimeter of the body part, which may be defined as a distance between two points being constrained to remain on a 3D surface.

The length of the part of the body, for example the length of the foot (size), can be determined directly from one or more images, knowing the length between two points in the image, and knowing the correspondence between the points of the image and 3D points in the world landmark with the calibration matrix.

The perimeter of a 3D surface of the portion of the body of interest is preferably calculated from several images according to a method based on a principle known in the field of stereology, described in Bobenko et al., 2008 ("Discrete Differential"). Geometry, Bobenko, "AI, Schroder, P., Sullivan, JM, Ziegler, GM (Eds.), Birkhauser, 2008, DOI 10.1007 / 978-3-7643-8621-4, 149). The method is described later in connection with FIGS. 4A and 4B. The perimeter can also be estimated from a single image. In this case, we measure a length in the image which is an approximation of the perimeter of the part of the body. This approximation can be satisfactory if, for example, it can be assumed that the body part to be measured is similar to a cylinder.

The calculations of the calibration step and the determination of the characteristic dimensions of the foot can be carried out directly by the image acquisition device, in the case where the latter comprises calculation means as is the case with a smartphone conventionally comprising a laptop. In this case the smartphone includes the program for processing images for calibration and for measuring the characteristic dimension of the foot. Alternatively, these calculations can be performed remotely, by an external computer-type device with the program for calibration and measurement. In this case, the information is transmitted from the image acquisition device to the computer by wire connection, for example via a USB key, a memory card, etc., or by wireless connection, for example WIFI, cellular etc. .

In the case of a transfer of images, it is conceivable to anonymize the images by removing on the images before their transfer any distinctive sign, for example moles or tattoos.

Figures 2A and 2B illustrate an implementation of the method of measuring a length according to the invention from an image.

According to this implementation, at least one characteristic dimension of the part of the body is determined from a single image and from the calibration matrix, the latter making it possible to carry out the correspondence between a point of the image and a 3D point. located in the plane of the sights and expressed in the world landmark.

As in FIG. 1A, a foot 10 is placed on a 2D chart 30 bearing identifiable markers 40. The picture is taken using the smartphone 20. A photograph of the stand 10 and the screen 30 is acquired by the smartphone 20 , so that the image contains entirely the characteristic dimension of the foot 10 that one wishes to determine, ie the length of the foot 50, corresponding to the size, as well as at least three markers 40 of the target. 30 is a single sheet of white A4 paper with markers 40 in the form of black circular pellets at the four corners, as shown in FIG. 1B.

For the calibration step, the positions in the image 21 of at least three markers 41 of the target 31 are determined, as previously explained. Knowing the position of the markers 40 of the target 30 in the world coordinate system, the calibration matrix of the photographic sensor is established which makes it possible to match the positions of the points in the image and the 3D positions of the points in the plane of the image. the target in the world landmark (also called object space or object landmark). This calibration method is known (Hartley and Zisserman, 2004: "Multiple View Geometry in Computer Vision", 2004, Part I "Geometry and Single View Geometry Camera", Cambridge University Press, pp. 151-233).

Once the calibration step is completed, the actual length of the foot 50 is determined from the length 51 extracted from the image 21. For this step, it is assumed that the observed object, ie the foot, is in the plane formed by the test pattern 30. The measurements are then very satisfactory for all the points of the foot present in the plane of the test pattern, and more and more approximate when the points are moving away from this plane.

According to this implementation, a dimension of length type is preferably determined, i.e a Euclidean distance between two points. In the case of the measurement of a foot, other types of dimensions characteristic of the length of the foot 50 (size) can be determined according to this implementation, such as for example the length and width of different parts of the foot of the foot. preferably measured at the base of the foot (points of the foot on the target), such as the dimensions referenced 2b, 2c, 2d, 3b, 3c, 3d, and 9 in Table 1 below, and partly illustrated in FIG. 5. According to this implementation, it is also possible to determine a perimeter of a part of the body, if we make a hypothesis on the geometrical shape of the part of the body in question, for example if we consider that said part has a cylindrical shape . In this case we can approximate the real perimeter by a single measurement of the apparent diameter of the body part in the image. Figures 3A and 3B illustrate an implementation of the method of measuring a length according to the invention from two images.

According to this implementation, at least two images are acquired with the image acquisition device placed in two different positions so that each image contains at least one characteristic dimension to be determined, and the characteristic dimension is determined by triangulation at from said at least two photographs.

This implementation is based on a triangulation approach for calibration, known and for example described in Hartley and Zisserman, 2004 ("Multiple View Geometry in Computer Vision", 2004, Part II "Two-View Geometry", Cambridge University Press, pp. 237-308).

As in FIGS. 1A and 2A, a foot 10 is placed on a 2D chart 30 having identifiable markers 40. The picture is taken using the smartphone 20.

At least two images 21 and 22 of the foot 10 and the test pattern 30 are acquired by the smartphone 20 placed in two different positions (a) and (b), so that each image (21, 22) completely contains the characteristic dimension of the foot 10 that one wishes to determine, ie the length of the foot 50 (size), and at least three same markers 40 of the test chart 30. In the images 21 and 22, the length of the actual foot 50 is referenced respectively 51 and 52, the foot 10 is referenced 11 and 12, the three markers 40 of the test pattern 30 are referenced 41 and 42. The pattern 30 is identical to that described for Figure 2A.

Thus, for each characteristic dimension that it is desired to determine, at least two images acquired by the smartphone 20 in different positions are available. By estimating transformation T (represented by a double arrow in FIG. 3A) between the two positions (a) and (b) of the two images 21 and 22 in the world coordinate with the aid of the target 30, the real coordinates 3D can be determined points of the image.

The estimation of the transformation T can be carried out according to different methods. The use of a 2D test pattern with at least 3 markers visible in the images is required. The estimation of the transformation T can be carried out as follows: in order to be able to estimate the movement of the smartphone between two shots, a paper pattern on which four markers are located is used. The movement of the image acquisition device, e.g. the smartphone, from one view to another is determined by the transformation matrix for passing four markers from the first image to the second image.

Let M be the displacement matrix 3x3 with my coefficient at line i and at column j:

m ₁₂ m ₁₃

M = m ₂₁ m ₂₂ m ₂₃

m ₃₁ m ₃₂ m ₃₃

Let Gl, G2, G3 and G4 be the markers of the image 1, and D1, D2, D3, D4 the corresponding markers of the image 2. The values of the coefficients my are obtained by mapping the markers between the two images. as a system and solving it by a less square type method.

The system to solve is written as:

Dl _x Dl _y 1 0 0 0 -G1 _X * D1 _X -Gl _x * Dl _y -Gl _y = 0

0 0 0 Dl _x Dl _y 1 -Gl _y * Dl _x -Gl _y * Dl _y -Gl _y = 0 etc.

The transformation in space is then defined as follows:

Rotation with respect to Z axis = asin (m ₂ i)

Translation with respect to the X axis = m ₁₃

Translation relative to the Y axis = m ₂₃

- Translation with respect to the Z axis = m ₃₃

Scale factor along the X axis = mu / cos (asin (m ₂ i))

Scale factor along the Y axis = m ₂ i / cos (asin (m ₂ i))

Knowing the correspondence between a 3D point in the world coordinate system and a point in each of the two images (calibration matrix), we can then determine a distance between two points of space from the two images. According to this approach, it is not assumed that the object must be in the plane formed by the target, unlike the implementation with a single image.

On the other hand, the measurement error evolves in the same way as for the implementation with an image described with reference to FIGS. 2A and 2B: the measurements are very satisfactory for all the points of the foot close to the plane of the sight, and more and more approximate when the points are moving away from this plane.

According to this implementation, it is thus possible to determine a characteristic dimension of the portion of the image body, preferably a dimension of length type, i.e. a Euclidean distance between two points, knowing the transformation between two images. In the case of the measurement of a foot, other types of characteristic dimensions that the length of the foot 50 (size) can be determined according to this implementation, such as for example the length, width, height of different parts. of the foot, such as the dimensions referenced 2b, 2c, 2d, 2e, 3b, 3c, 3d, 3e, 4b, 4c, 5a, 5b, 6b, 6c and 9 in Table 1 below, and partly illustrated in FIG. figure 5.

According to this implementation, it is also possible to determine a perimeter of a body part, if one makes a hypothesis on the geometric shape of the part of the body in question, for example if it is considered that said part has a cylindrical shape. In this case we can approximate the real perimeter by a single measurement of the apparent diameter of the body part in the image. According to one implementation of the measurement method, at least one perimeter-type characteristic dimension is determined from n photographs taken in n different positions around the part of the body to be measured, n being greater than or equal to two, typically between 3 and 10 photographs, preferably between 3 and 5 photographs.

In particular, the perimeter of a part of the body is determined by measuring on each photograph i, i ranging from 1 to n, the length of the apparent diameter di, and the perimeter p is estimated by means of the following formula (IV):

This estimate is based on a known principle of the field of stereology, for example mentioned in Bobenko et al., 2008 ("Discrete Differential Geometry, Bobenko," AI, Schroder, P., Sullivan, JM, Ziegler, GM (Eds .), Birkhauser, 2008, DOI 10.1007 / 978-3-7643-8621-4, p.149), based on a lemma according to which the length of a curve γ c S ^dl is equal to π times the mean intersections of γ with large hyperspheres S ^{d ~ 2} . This estimate provides a satisfactory measure, especially in the case where the 3D surface is convex and the number of images n tends to infinity.

FIGS. 4A and 4B illustrate an example of such an implementation, in which three images 21, 22 and 23 are acquired around a foot 10 placed on a target 30 carrying markers 40. The pattern is identical to that described in relation to the preceding figures. The smartphone 20 is therefore placed in 3 different positions (c), (d), and (e) around the foot 10. In each of the images 21, 22, 23, the instep to be measured is visible, and than the 3 markers 40 (references 41, 42, 43) of the target 30 (references 31, 32, 33).

The perimeter 60, at the instep, is determined by measuring in each image 21, 22, and 23, the apparent diameter 61, 62 and 63, and applying the formula (IV).

According to this implementation, the calibration step is performed as described in relation to FIGS. 2A and 2B. Once the calibration matrix is established, it is possible to determine the actual length of the apparent diameter di measured in the image, and thus to estimate the perimeter using the formula (IV). According to another implementation, the measurement method comprises the following steps:

the plane formed by the 2D target is expressed in the world marker, for example with the knowledge of the position of at least 3 markers of the target;

at least one acquired image is superimposed on a generic 3D model of the part of the body to be measured, the model being previously calibrated with real generic dimensions of the part of the body to be measured, and;

the projected 3D model is deformed on the image so as to make coincide characteristic points belonging to the plane formed by the 2D pattern of the photograph and the 3D model;

the characteristic dimension, length or perimeter, is determined from the deformed 3D model.

The deformation of the 3D model can be done manually, with the intervention of an operator who modifies the points of the model using a pointing device or automatically by implementing an algorithm that adjusts the position of the points to satisfy a given criterion. The deformation of the 3D model is global, that is to say that from the mapping of the characteristic points belonging to the plane formed by the 2D pattern of the photograph and the 3D model, the 3D model is modified da ns his outfit. For example, if we make the base of the 3D model coincide with the length of the foot, we deform the entire 3D model of the foot in proportion to the transformation of the base of the 3D model. According to another implementation of the method, the acquisition of the photographs is guided by means of visual indications, such as the transparency display in the photograph of a drawing of the part of the body and the sight, or by means of sound indications such as a beep or tactile indications such as vibrations. These indications may for example indicate that the gesture made for the acquisition is not the right one, in which case the person who manipulates the image acquisition device will modify the shooting.

The measuring method according to the invention is advantageously applied to the measurement of a foot, as illustrated in the various figures, and makes it possible to determine a characteristic dimension of the foot which is a characteristic dimension useful to a box, preferably selected from a length, a width, a height, a perimeter of a part of the foot.

At least one characteristic dimension of at least one measurement point of the following foot is determined with the method according to the invention:

- the shoe size ;

- the size of the fingers;

- the instep;

- the entrance

- malleolus;

- ankle ;

- the strong point of the calf;

- the knee; and

- the little toe-heel.

These different measurement points are listed in Table 1 below, referenced from 1 to 9, and their position is illustrated in Figure 5. In Figure 5, the diagram (A) shows a top view of the foot, and Diagrams (B), (C) and (D) foot profile views. The different characteristic dimensions associated with each measurement point are also listed in Table 1.

Preferably, at least the size is measured, even more preferably at least the size, the size at the fingers, the instep, the entry, and the malleolus are measured, and even more preferably, all these points of measurement are measured. measuring, that is to say, at least one characteristic dimension for each of said measurement points, and preferably all the dimensions listed in Table 1 associated with each measurement point. Point Designation Type

1 size

2a.périmètre

2b.Distance of the heel to the size at the fingers of the inside of the foot

2 Finger size 2c. distance from the heel to the size of the fingers of the outside of the foot

2d.width of the foot to the size of the fingers

2nd.Height of the foot to the size of the fingers

3a.périmètre

3b.Distance of the heel to the size of the fingers of the inside of the foot

3 Neck 3c. distance from the heel to the size of the fingers of the outside of the foot

3d.largeur

3rd. height

4a.périmètre

4 Input 4b.width

4c. height

Height of the internal malleolus

5 Malloleole

5b. height of the external malleolus

6a.périmètre

6 Ankle 6b.width

6c. height

7 Strong point of the Perimeter calf (can be approximated by an ellipse)

8 Sub Knee Perimeter (can be approximated by an ellipse)

9 Small toe-heel Distance from heel to toe

Table 1

According to one implementation of the method for the measurement of the foot, at least two images acquired in a simple gesture, which may comprise at least one of the following movements (a) to (d), are photographed:

(c) a rotational movement of the photographic acquisition device around the ankle; (d) a rotational movement photographic acquisition device around the leg.

At least one of the characteristic dimensions of the following measurement points is then determined according to the movements of the image acquisition device during the acquisition:

- the size of the fingers (2) and / or the instep (3) from the photographs acquired according to the movement (a);

- the size (1) and / or the size of the fingers (2) and / or the instep (3) and / or the entry (4) and / or the malleolus (5) from the photographs acquired according to the movement (b);

- the inlet (4) and / or the peg (6) from the images acquired according to the movement (c);

- the strong point of the calf (7) and / or the knee (8) and / or the little toe-heel (9) from the photographs acquired according to the movement (d).

Preferably, in order to determine a large number of characteristic dimensions of the foot, for example dimensions for all the measuring points 1 to 9, the images are acquired by performing 5 gestures corresponding to the movements (a) to (d).

Figure 6 illustrates the described gestures associated with the acquisition of images. In identifiable markers 40, before taking pictures. In diagrams (B) to (F), the movements of the smartphone 20 are indicated by arrows. Diagram (B) illustrates the translation movement 70 of the smartphone 20 above the foot 10 and the test pattern 30, performed in a substantially horizontal plane and in a direction perpendicular to the length of the foot so. This movement makes it possible to determine characteristic dimensions for the size of the fingers (2) and the instep (3). Diagram (C) illustrates the translation movement 71 of the smartphone 20 which is a translation movement inside the foot, in a substantially vertical plane and in a direction parallel to the length of the foot. Shooting according to this movement makes it possible to determine characteristic dimensions relating to the size (1), the size of the fingers (2), the instep (3), the entry (4) and the malleolus (5). Shooting according to an identical translational movement but outside the foot, as shown in diagram (D), makes it possible to determine characteristic dimensions of the same measurement points. Images taken according to the rotational movement 73 around the peg illustrated in the diagram (E), allow measurements of the inlet (4) and the peg (6). Finally, the diagram (F) illustrates a rotational movement 74 around the leg wider than that around the ankle, allowing measurements at the strong point of the calf (7), the sub-knee (8), and the small toe-heel (9).

It is understood that the images acquired according to different movements can be exploited to determine a given characteristic dimension. This very simple gesture, which can be carried out by the person himself, makes it possible to provide all the information necessary for the measurement according to the method, with a view to delivering the necessary measurements to a bootmaker for the manufacture of tailor-made shoes.

During gestures, the triggering of the taking of images can be carried out by the user or automatically by the image acquisition device. In this case, an automatic tracking in the image of the test pattern can be performed, and / or a tracking information inclinations and displacements through an accelerometer can also be achieved.

The various implementations described can be combined without departing from the scope of the present invention. By way of example, it is possible to implement in the same method both the determination of a length from a single image, and / or the determination of a length from several images, and / or determining a perimeter from n images. Many combinations are possible.

One aspect of the invention relates to a tailor-made manufacturing process of a shoe, in which at least one characteristic dimension of the foot is determined by the measurement method described, and a tailor-made shoe is produced from said less a characteristic dimension of the foot. Preferably at least the size is determined, and even more preferably the characteristic dimensions of all the following measuring points: the size, the size to the fingers, the instep, the entrance, the malleolus, the ankle, the strong point of the calf, the knee, and the small toe-heel, to provide these measures to the bootmaker for the manufacture of the shoe.

Preferably the tailor-made shoe is manufactured from the characteristic dimensions of all the measurement points listed above.

The measuring method according to the invention can advantageously be applied to the measurement of another part of the human body than the foot, such as a hand or a neck.

Another aspect of the invention relates to the manufacture of a fashion adapted to the morphology of a part of the human body, in which at least one characteristic dimension of said part of the body, preferably of one hand, is determined. neck or foot, by the measurement method described, and the tailor-made fashion accessory is made from said at least one characteristic dimension. Preferably, the diameter of a finger of the hand, the diameter of the wrist, the diameter of the neck, or the diameter of a part of the foot such as the ankle are measured, for example to make an over-sized jewel such as a ring. , a bracelet, a necklace, or any other finery. One can also measure the dimensions of a hand necessary for example to make tailor-made gloves.

Claims

1. Device for measuring a part of the human body from digital photographs, without 3D reconstruction of said part of the body, comprising the following steps: the acquisition with the aid of a photographic acquisition device of at least one photograph of said part of the body and a known 2D pattern having at least three markers, such that said photograph contains at least one characteristic dimension of said part of the body to be determined and the three markers of said test pattern;

calibrating the photographic acquisition device from said at least one photograph and at least three markers of the known 2D pattern by establishing a calibration matrix allowing the correspondence between a point of said photograph and a 3D point expressed in a world landmark;

determining said characteristic dimension of said body portion from said at least one photograph and said calibration matrix.

The method of claim 1, wherein said at least one characteristic dimension of said portion of the human body is a Euclidean distance between two points of said body portion or a perimeter of said body portion.

3. Method according to one of the preceding claims, wherein is determined at least one characteristic dimension of said body part from a single photograph and the calibration matrix, said matrix for performing the correspondence between a point of said photograph and a 3D point located in the plane of the target and expressed in the world landmark.

4. Method according to one of claims 1 to 2, wherein one acquires at least two photographs with the photographic acquisition device in two different positions so that each photograph contains said at least one characteristic dimension to be determined, it is estimated the transformation between the positions of the two photographs during the calibration, and determining said at least one characteristic dimension knowing said transformation.

5. Method according to the preceding claim, wherein there is determined at least one Euclidean distance characteristic dimension between two points from two photographs, said two photographs being acquired in a translational movement of the photographic acquisition device.

6. Method according to one of the preceding claims, in which at least one perimeter-type characteristic dimension is determined from n photographs taken in n different positions around the part of the body, n being greater than or equal to 2 and preferably between 3 and 10 photographs.

A method according to claim 6, wherein a perimeter of a body part is determined by measuring on each photograph i, i ranging from 1 to n, the length of the apparent diameter di in the photograph i, and the perimeter is estimated p by the following formula:

P = -Σ ^d i

n i = i

8. Method according to one of the preceding claims, wherein the photographic acquisition device is a camera of a smart phone.

9. Method according to one of the preceding claims, wherein the photographs are transmitted to a remote computer to perform the steps of calibration and determination of said at least one dimension characteristic of the human body.

10. Method according to one of the preceding claims, wherein:

we express the plane formed by the 2D chart in the world landmark;

the at least one photograph is superimposed on a generic 3D model of the part of the body to be measured, said model being previously calibrated with real generic dimensions of the part of the body to be measured, and;

said 3D model is deformed on the photograph in such a way as to coincide characteristic points belonging to the plane formed by the 2D pattern of the photograph and the 3D model;

said at least one characteristic dimension is determined from the deformed 3D model.

11. Method according to one of the preceding claims, wherein the acquisition of the photographs is guided by means of visual indications, such as the transparency display in the photograph of a drawing of the part of the body and the sight , or by means of audible indications such as a beep or tactile, such as vibrations preferably signaling that the gesture made for the acquisition is not the right one.

12. Method according to one of the preceding claims for the measurement of a foot, wherein said at least one characteristic dimension of the measured foot is a characteristic dimension useful to a box, preferably selected from a length, a width, a height , a perimeter of a part of the foot.

13. The method of claim 12, wherein determining at least one characteristic dimension of at least one measurement point of the following foot:

- the shoe size ;

- the size of the fingers;

- the instep;

- the entrance

- malleolus; - ankle ;

- the strong point of the calf;

- the knee; and

- the little toe-heel,

and preferably at least one characteristic dimension for each of said measuring points.

14. Method according to one of claims 12 and 13, wherein one acquires at least two photographs in at least one of the following movements (a) to (d):

(d) a rotational movement of the photographic acquisition device around the leg, and in which at least one of the characteristic dimensions of the following measurement points is determined according to the movements of the photographic acquisition device during the acquisition of the photographs:

the size of the fingers and / or the instep from the photographs acquired according to the movement (a);

the size and / or the size of the fingers and / or the instep and / or the entrance and / or the malleolus from the photographs acquired according to the movement (b);

the entrance and / or ankle from the images acquired according to the movement (c);

the strong point of the calf and / or the under knee and / or the small toe-heel from the photographs acquired according to the movement (d).

15. A method of manufacturing a shoe, wherein:

at least one characteristic dimension of the foot is determined by the method according to one of the preceding claims, preferably at least the size, and even more preferably the characteristic dimensions of all the following measuring points: the size, the size at the fingers, the instep, the entrance, the malleolus, the ankle, the strong point of the calf, the under knee, and the little toe-heel; and

a tailor-made shoe is produced from said at least one characteristic dimension of the foot, and preferably from the characteristic dimensions of all said measuring points.

16. Method according to one of claims 1 to 11 for measuring a hand or a neck.

17. A method of manufacturing a fashion accessory adapted to the morphology of a part of the human body, wherein:

at least one characteristic dimension of said part of the human body is determined by the method according to one of claims 1 to 11, preferably at least one characteristic dimension of a hand, a neck, or a foot, and preferably the diameter of a finger of the hand, the diameter of the wrist, the diameter of the neck, or the diameter of a part of the foot such as the ankle; and