Computer-implemented method for measuring an elongation of an object and associated device

Abstract

The present disclosure relates to a computer-implemented method for measuring an elongation of an object (100), the method comprising the following steps: acquiring an image (E1) comprising an object (100) in a deformed position and an impression (101) attached to the object (100), wherein the impression (101) is non-deformable relative to the object (100), and wherein the object (100) comprises a marker (102); and, on the basis of the acquired image and the resting dimensions of the object (100), determining (E2) an elongation ( / <) of the object (100) by tracking the marker (102) of the object (100) relative to the impression (101), wherein the resting dimensions of the object (100) are defined relative to the marker (102) and relative to the impression (101).

Description

[0001]Computer-implemented method for measuring an elongation of an object and associated device TECHNICAL FIELD This disclosure concerns computer-based image analysis methods, in particular image analysis methods for monitoring a deformation of a compression garment. STATE OF THE ART Certain computer-based image analysis methods make it possible to measure a deformation of an object. To do this, a visible marker in an image is associated with the object, for example by printing the marker on the object. Indeed, since the marker deforms at the same time as the object, it makes it possible to monitor its deformation. These methods could be used in particular in the medical field to monitor treatment for a chronic illness causing swelling of a limb, for example edema. In this case, to treat the illness, a patient wears a compression garment that covers the affected limb. However, to monitor the illness, a doctor measures with a tape measure,a scanner or by water displacement an evolution of a circumference of the affected limb. Thus, to implement this measurement, the tools used by the doctor could be substituted by a tracking of the landmark which deforms at the same time as the compression garment. However, these methods have limits in terms of precision. Indeed, the tracking can be distorted depending on the point of view with which the image was taken. Indeed, when the camera lens is not in front of the pattern, there can be a perspective effect which distorts the pattern in the image. Therefore, the distortion caused by the perspective effect can significantly affect the accuracy of the measurements. In addition, all landmarks must be captured by a sequence of images,which requires moving the camera around the object to scan its surface or rotating and tilting the object in front of a fixed camera. These methods also require either the presence of a second person (as is the case for 3D scanners), or a specific and calculated positioning of the camera in relation to the object. They are therefore unsuitable for medical use. Indeed, certain pathologies require regular monitoring and justify that it be carried out by the patient himself, that is to say without systematically going to a health establishment, in order to improve the treatment of the pathology but also the costs generated by this care. Some solutions which aim to choose a pattern less sensitive to this disturbance or to use an image processing method in order to restore the image in perspective in the measurement plane have been proposed. However,These solutions only limit this effect without eliminating it and partially address the aforementioned drawbacks. Another solution would be to keep the camera lens facing the pattern during image acquisition. However, such a solution can be difficult to implement when the object is moving during acquisition, particularly when the user of the compression garment moves his leg or arm. This solution lacks precision and may be incompatible in the case of treating pathologies such as edema. In addition, it does not address all the aforementioned drawbacks. Another solution consists of using a property of the cross-ratio (better known by the English acronym "cross-ratio"). Indeed,This is a mathematical equation that is invariant in projection. That is to say, a cross-ratio of four aligned points in a perspective image is equal to a cross-ratio of the same four aligned points in an image without perspective effect. However, although this method is effective for fixed objects, it becomes difficult to apply in the context of an object that is deformed due to the variations in lengths between these four points that are induced by the deformations of the object. Indeed, these variations add unknowns to the equality and make its resolution difficult. GENERAL DISCLOSURE An aim of the invention is therefore to improve the monitoring by image analysis of the deformation of the object. To this end, according to a first aspect of the present disclosure, a computer-implemented method is proposed for measuring an elongation of an object,the method comprising the following steps: acquiring an image comprising an object in a deformed position and an imprint connected to the object, the imprint being non-deformable relative to the object, the object comprising a reference frame; and from the acquired image and dimensions of the object at rest, determining an elongation of the object by tracking the reference frame of the object relative to the imprint, the dimensions of the object at rest being defined relative to the reference frame and relative to the imprint. Thus, by defining an non-deformable reference from which the object stretches, the mode of deformation of the object is changed to a mode in which an equality of the cross-ratios becomes an equation which now comprises only one unknown. Consequently, it is possible to determine the elongation from this equation which does not depend on the perspective effect. Thus,an error factor in the measurement of the elongation is eliminated, which has the effect of improving the monitoring by image analysis of the deformation of the object. The method also makes it possible to choose the points which define the deformable segments in the cross-ratio at any location of the object visible on the image. It also makes it possible to carry out the measurement with a minimum of data. Indeed, the measurement is implemented only from an image of a portion of the object. It can be provided that the method includes a determination of a segment in the image, the determination of the elongation of the object taking place in the segment. The object can therefore be meshed to take into account the variations in elongation within the object. Thus, the precision is further improved, as is the determination of the dimension of the object as well as its volume. It can also be provided that the imprint includes two markers,the segment being defined between the two markers. It may also be provided that the two markers are fiduciary markers, barcodes, or QR codes. Thus, it is possible to distinguish the segments in a simple and reliable manner in the context of a computer implementation. It may be provided that the method comprises a step of measuring, from the elongation, a dimension of the object. It is therefore possible to measure a dimension of the object for a set of states between a resting state and a breaking state. In addition, it is possible to carry out this measurement precisely, that is to say that the precision of the measurement is of the order of the pixel. In addition, the repeatability of the measurement is improved. The measurement error in the image is also between 2% and 4%. The repeatability is also improved. In the case where the object is a compression garment, it is also possible for the user to carry out the measurement himself,without, for example, the intervention of a doctor. Therefore, the treatment of a pathology such as edema is improved by regular monitoring of the patient made possible thanks to the method. It can also be provided that the method includes the following steps: from the elongation, measurement of a circumference of the object; and from the measurement, determination of a volume of the object. It is therefore possible to measure a volume of the object for a set of states between a state of rest and a state of rupture. In addition, it is possible to carry out this measurement precisely, that is to say that the precision of the measurement is of the order of the pixel. The measurement error in the image is also between 2% and 4%. In addition, the repeatability of the measurement is improved. In addition, it is possible to carry out the measurement with a minimum of data. Indeed,the volume is calculated from a portion of the object visible on the image instead of performing a complete scan of the object to determine its volume. It may also be provided to determine from the measurement of the circumference of the object a pressure field of the object. Thus, thanks to the pressure field it is for example possible to evaluate the effectiveness of the compression garment, in particular for the treatment of a pathology such as edema, in real time and in a dynamic environment. It may also be provided to determine a normalized pressure field, for example expressed between zero as the lowest measured value and one as the highest measured value. This solution is particularly advantageous when it is difficult or even impossible to determine the pressure value in Pascal, or even in mmHg (millimeter of mercury) which is a unit commonly used for compression garments,but that one still wishes to have an idea concerning the pressure distribution within the garment, for example to check whether the stocking applies strong pressure at the distal end and progressively weaker pressure towards the proximal end. It can be provided that the imprint comprises two distinctly connected patterns on the object. In this case, the use of two imprints makes it possible to position the aligned points on the imprints. Thus, the length of a single segment is unknown when using the cross-ratio which further improves the method. It can be provided that the method is implemented by a terminal and in which the object is a compression garment, the marker is formed by two lines and the imprint is formed by a strip. Indeed, the method is suitable for a medical application, for example in monitoring pathologies such as edema, lymphedema,deep vein thrombosis or any other pathology causing swelling or atrophy of a limb. In this case, the patient wears a compression garment on the arm or leg to treat these pathologies. He can then measure with a terminal, for example his mobile phone, his compression garment independently, without the intervention of a doctor, to monitor the evolution of his pathology. Consequently, the garment is quickly and easily analyzed by the phone which is capable of implementing the process. Thus, the process is implemented without the use of expensive and uncommon equipment and it makes it possible to make the monitoring of pathologies by a patient accessible. The measurement is precise, that is to say that the precision of the measurement is of the order of a pixel, unlike a measurement taken by a tape measure whose precision is of the order of ten millimeters,or even a few centimeters. The measurement error in the image is also between 2% and 4%. The repeatability of the measurement is also improved. In addition, the process improves the speed of the measurement compared to other existing methods. In fact, the time saving is estimated at 10 minutes on average compared to the use of a tape measure. In addition, the process improves the safety of the measurement because it is implemented without contacting a measuring tool with the arm or leg. It is also possible for the user to carry out the measurement themselves, for example without the intervention of a doctor. Therefore, the treatment of a pathology such as edema is improved by regular monitoring of the patient made possible thanks to the process. It can also be provided that the band is between the two lines, or the two lines are adjacent. Thus,it is possible to apply the method to any markers present on the image. It may also be provided that the imprint is formed of a first strip and a second strip, a first line being taken on one end of the first strip and a second line being taken on one end of the second strip opposite the end of the first strip. It may also be provided that the strip comprises markers, the markers being aligned on the strip. Thus, the accuracy of the measurement can also be further improved in the case of a medical application. According to a second aspect of the present disclosure, there is provided an assembly comprising: an object comprising a marker; and an imprint connected to the object, the imprint being non-deformable relative to the object, the assembly being configured to allow determination of an elongation of the object by tracking a marker of the object relative to the imprint. According to a third aspect of the present disclosure,a device for measuring a deformation of an object is proposed, the device comprising: an assembly comprising: an object comprising a reference mark; and an imprint connected to the object, the imprint being non-deformable relative to the object, the assembly being configured to determine an elongation of the object by tracking a reference mark of the object relative to the imprint; and a terminal configured to: acquire an image comprising the assembly; and from the acquired image and dimensions of the object at rest, determine an elongation of the object by tracking the reference mark of the object relative to the imprint, the dimensions of the object at rest being defined relative to the reference mark and relative to the imprint. DESCRIPTION OF THE FIGURES Other characteristics, aims and advantages will emerge from the description which follows, which is purely illustrative and non-limiting,and which must be read in conjunction with the attached drawings in which: Figure 1 schematically represents a device for measuring a deformation of a compression garment worn by a user; Figure 2a, Figure 2b, Figure 2c and Figure 2d schematically illustrate several geometric configurations of the imprint and the reference mark; Figure 3a, Figure 3b, Figure 3c and Figure 3d schematically illustrate markers respectively on the imprint of Figure 2a, Figure 2b, Figure 2c and Figure 2d; Figure 4 illustrates several types of markers; Figure 5 schematically illustrates a mode of implementation of a method for measuring a deformation of an object; Figure 6a, Figure 6b, Figure 6c and Figure 6d illustrate four aligned points positioned on a print and a reference mark in the case of an object at rest; andFigure 7a, Figure 7b,Figure 7c and Figure 7d illustrate four aligned points positioned on the imprint and the reference mark in the case where the object of Figure 6a, Figure 6b, Figure 6c and Figure 6d is deformed. DETAILED DESCRIPTION A device 1 for measuring an elongation of a compression garment 100 is illustrated as an example in Figure 1. The compression garment 100 is configured to be worn by a user 2 on a limb, for example an arm 21 and / or a leg 22, for example by fitting. It is suitable for a medical application, for example in monitoring pathologies such as edema, lymphedema, deep vein thrombosis or any other pathology causing swelling or atrophy of a limb,thanks to the compression force exerted by the garment on the limb affected by the pathology. The compression garment 100 is of substantially cylindrical geometry and is formed of a flexible fabric in order to be able to stretch the garment when fitting and to compress the limb when the garment is fitted. The measuring device 1 is also suitable for other compression garments, for example a t-shirt or trousers whose shape fits several parts of the user 2. In addition, the device 1 is neither limited by a type of fabric used (it can be a unidirectional or bidirectional textile fabric), nor by a material of the fabric (fiberglass, Kevlar, cotton, etc.). The device 1 is also suitable for other types of objects which have a Young's modulus, therefore which obey Hooke's law. It may be an object comprising an inflatable material, such as a balloon,a parachute or an inflatable structure. The device 1 may also be suitable for measuring an elongation of the skin of the user 2 in the context of monitoring an evolution of dimensions or a volume of a limb, for example in the case of a potential inflammation of the tissues of a limb or monitoring a recovery of muscle mass of an atrophied or injured limb. It may also be suitable for measuring an elongation of a civil construction, a sail or a material by tensile testing in general. The device 1 comprises an assembly 10 configured to monitor the elongation of the compression garment 100. The assembly 10 comprises: - the compression garment 100; and - an imprint, formed of two strips 101a, 101b in this example,connected to the compression garment 100. The print can be connected to the compression garment by weaving. It is also possible to connect the print to the garment by other methods. For example, by laser beam by applying glue to the print and heating the print positioned on the garment by air convection. Other heat sources can be used, such as laser. The print can also be connected by screen printing. The print is distinct from the garment 100. The print can be distinguished from the garment by its color. In the example in Figure 1, the print is black and can be distinguished from the white compression garment. Of course, the print can be any color, it can even be the same color as the garment but a different shade, for example by different gray levels. Other visual properties of the garment can also be used to distinguish the print from the garment,by using filters or different types of light, for example by highlighting the print under ultraviolet or infrared light. It is also possible to make it distinct by varying the contrast, the print protruding from the garment. The print is non-deformable relative to the garment 100. In other words, when the garment is stretched, the print remains fixed while a fabric of the garment stretches. To achieve this, a Young's modulus of the print is greater than that of the measured object. It can be greater by up to a factor of ten compared to that of the material of the measured object and, in the example of the compression garment 100, by up to a factor of eight compared to the fabric of the garment. For example, the impression can be made of nylon, whose Young's modulus is between 2 GPa and 4 GPa, or polyester, whose Young's modulus is between 3 GPa and 5 GPa, while the compression garment is made of elastane,whose Young's modulus reaches 0.6 GPa. In the case where the Young's modulus of the imprint is close to the Young's modulus of the object, for example when the imprint is also in a fabric having a Young's modulus close to that of the garment, it is possible to stiffen the imprint by increasing a density of the fabric by a factor of ten compared to a density of the fabric of the garment, for example by embroidery. It is also possible to stiffen the fabric imprint by using a different weave from that used for the compression garment. According to another example, in the case of an object comprising an alloy or a ceramic, it is possible to stiffen the impression by subjecting it to a heat treatment using quenching or tempering followed optionally by annealing. Thus, in this example, when the compression garment 100 deforms, it is possible to see the bands 101a, 101b move apart or move closer together relative to a position of the bands 101a,101b in a resting state of the compression garment 100. For example, when a volume of the user's limb 2 increases over time, the garment undergoes an elongation which will separate the bands. It is then possible to visually follow an evolution of the volume of the limb relative to a resting position, for example when the garment is worn for the first time, by monitoring a movement of the bands 101a, 101b on the garment 100. Figure 2a, Figure 2b, Figure 2c and Figure 2d illustrate in detail the assembly 10 according to several embodiments. In these figures, a portion of the compression garment 100 is shown. In the embodiment illustrated in Figure 2a, the garment comprises a marker,formed of two separate lines 102 of the band 101. A band 101 between the two lines is connected to the compression garment 100 instead of two bands as illustrated in Figure 1. In the embodiments illustrated respectively in Figure 2b and Figure 2c, the two lines 102 are adjacent on the garment and they follow each other. They can also be positioned in front of the band 101 or behind the band 101. The mark can be made by contrast ink which does not affect the elasticity properties of the garment, for example intersecting the lines 102 on the garment 101. Thus, the visual monitoring of the deformation is done by monitoring a displacement of the lines 102 relative to the band 101. The mark can also be a grid drawn on all or part of the garment 101. Of course, the mark can be any other geometric pattern which extends mainly or part of the garment. Of course,the imprint can also be any other geometric pattern. For example, a cross, a triangle, a square. The imprint and the mark can also have different thicknesses and dimensions on the object. The mark can also be any element projecting from the garment or from an object in general. Indeed, in the embodiment illustrated in Figure 2d which is similar to that of Figure 1, the mark is formed by two lines 102 facing each other and taken on one end of each of the strips 101a, 101b. Thus, the visual tracking is done in a manner similar to that described above in the example illustrated in Figure 1. Consequently, according to the aforementioned specific cases, the mark can be distinct from the imprint just as it can be confused with the imprint without departing from the scope of the present description. It can be provided that the mark is generated by computer,for example by superimposing the marker on an image of the object and the imprint obtained by image acquisition means. The marker may also be a combination of a portion visible on the garment and a computer-generated portion. It may also be provided to combine several patterns of imprints and markers for the same object. For example, on the same compression garment, a first portion of the garment may correspond to the embodiment of Figure 2a and a second portion of the garment may correspond to the embodiment of Figure 2d. The imprint may also comprise markers. In the embodiments illustrated in Figure 3a, Figure 3b and Figure 3c, the markers are placed on the strip 101. In the embodiment illustrated in Figure 3d, the markers are positioned on one of the strips 101a, 101b. They may also be positioned on both strips 101a, 101b.101b. The markers are geometrically identical in pairs and delimit a portion of the band. In these examples, the markers are QR codes. The markers may also be other fiduciary markers, a set of examples of which are illustrated in a non-limiting manner in Figure 4. The device 1 further comprises a terminal 11 configured to obtain an image of the assembly and to measure the elongation of the compression garment 100 from the image. In the example illustrated in Figure 1, the terminal 11 is a mobile phone. It may also be a computer,or an image acquisition device such as a camera or a video device. It may also be any other means capable of acquiring images. The terminal may further be connected to a database 12 remote from the terminal 11. The terminal may connect to the database 12 and exchange data with the database 12 via WiFi connection or via mobile telephone network (4G or 5G). The terminal may also be configured to display data on a screen, for example the deformed compression garment 100. To measure the elongation of the compression garment, the terminal is configured to implement a measurement method in which, with reference to FIG. 5, the following steps are implemented. The method is implemented as an example in the case of a compression garment. Of course, the measurement method may be implemented for any object that obeys Hooke's law. Furthermore, the method is implemented by a terminal. However,this is a non-limiting example and the method is suitable for being implemented by computer in a general manner. During a step E0, an authentication of a serial number of the garment 100 is implemented by querying the database 12. If the authentication is valid, an image comprising a portion of the compression garment 100 in a deformed position and the print is acquired during a step E1, preferably in an adequate resolution. If the authentication is not valid, the database 12 sends an error message to the terminal 11. During a step E11,the image is improved by applying at least one of the following operations: correction of the image resolution; filtering; smoothing; image thresholding (better known by the English acronym “thresholding”); noise removal; histograms; histogram modifications; linear transformations; non-linear transformations; contrast modification; image restoration to remove degradations. During a step E12, a validity check of the markers 103 is implemented. For example, the terminal connected to the database 12 can verify a correspondence of the markers 103 with marker models pre-recorded in the database 12. During a step E13, a segment in the image is determined. The segment can be determined by a detection of two markers 103. In the case where there are at least four markers 103,several segments are determined. Each segment can also be determined by image processing. The methods for segmenting the image are known to a person skilled in the art and will not be detailed further. During a step E14, the image is cropped at the segment level. For example, the image is cropped by rotation and translation so that it is defined between the markers 103. In the case where there are at least four segments, depending on the precision required by the method, the image can be cropped at the two markers at the ends of the image. Consequently, all the markers are visible. According to another embodiment, the image can be divided into several parts each comprising one or more segments according to the desired precision and each part is then cropped. A detection of contours in the image is implemented during a step E15. For example,the contours corresponding to the imprint and the markers 103 are determined. The contours are highlighted in the image by removing the background colors in the contours or by other means, for example by highlighting or by changing the color of the contours or by transforming them into a binary image, in this case black and white. During a step E16, the imprint, the markers 103 and the landmarks 102 are identified in the image. During a step E17, a virtual line 104 and intersection points ^ ^^, ^ , , ^^ ^^ and ^ ^ ^^virtual lines with the strips 101a, 101b and the mark 102 are added by superposition in the image. It may also be provided to superimpose several virtual lines 104a, 104b, 104c and intersection points for each of the lines. During a step E2, an elongation of the garment 100 by tracking the mark 102 relative to the imprint is determined from the image and the dimensions of the garment at rest. Indeed, when the garment deforms, the mark moves away from the imprint. In the embodiment illustrated in Figure 6a and Figure 7a, the lines 102 move away on either side of the strip 101 during the deformation. In the embodiments illustrated respectively in Figure 6b with Figure 7b, and in Figure 6c with Figure 7c, the lines 102 each move away from the strip 101. In the embodiment illustrated in Figure 6d and in Figure 7d, the lines 102 on each of the strips 101a, 101b move away from each other.The previous examples show a mode of deformation of the garment in which the garment elongates relative to the strips. By analogy, the previous examples also show a mode of deformation in which the garment shrinks relative to the strips. In the first case, the markers move away from the strip or move away from each other, while in the second case, they move towards the strip or move towards each other. Thus, the Applicant found that it was possible to deduce an expression for the elongation from an equality between a cross-ratio (better known by the acronym "cross-ratio") of four aligned points in the image and a cross-ratio of four aligned points in an image without perspective effect. Indeed, in these modes of deformation, the equality includes only one unknown which corresponds to the elongation.An example of solving the equality that allows the elongation to be obtained is presented below in the worst case, that is to say that in which the band 101 is between the lines 102. In the example of solving, the equality is stated as follows:^. ^^ ^^^ ^^ ^^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ × = ^ ^ ^ ^^ ^^ × ^ ^^ ^ ^ ^^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ With ^ ^^ ^ , ^ ^^ ^ , ^ ^^ ^ , ^ ^^ ^ the intersection points in pixels taken in the image having undergone a perspective effect and ^ ^ ^, ^ ^ ^, ^ ^ ^, ^^ ^ points of intersection with the strip 101 and the lines 102 of the deformed garment without perspective effect. Indeed, the points ^ ^^ ^ , ^ ^^ ^ , ^ ^^ ^ , ^^ ^^ are a reconfiguration of the points ^ ^^, ^ ^ ^, ^ ^ ^, ^^ ^ under the perspective effect. The lengths ^ ^ ^ ^ ^ ^ , ^ ^ ^ ^ ^ ^, ^^ ^ ^ ^ ^ and ^ ^ ^ ^ ^ ^ are determined from Chasles relations in the following manner. ^ ^ ^ ^ ^ ^ = ^^ ^ ^ ^ ^ + ^^ ^ ^^ ^ ^ ^ ^ ^ ^ ^ = ^^ ^ ^ ^ ^ + ^^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ = ^^ ^ ^ ^ ^ + ^^ ^ ^ ^ ^ + ^^ ^ ^^ ^ Now, by making an assumption of a uniformly distributed elongation in the garment which is valid because the garment obeys Hooke's law, the lengths ^ ^ ^ ^ ^ ^ and ^ ^ ^ ^^ ^ are equal. Moreover, as the strip 101 is non-deformable relative to the reference mark, here in this case the lines 102, then the length ^ ^ ^ ^ ^ ^ is equal to the length ^ ^ ^ ^ . Therefore, the lengths ^ ^ ^ ^ ^ ^ , ^ ^ ^ ^ ^ ^, ^^ ^ ^ ^ ^ and ^ ^ ^ ^ ^ ^ are expressed as follows.^ ^ ^ ^ ^ ^ = ^ ⋅ ^^^^ + ^^^^^ ^ ^ ^ ^ ^ = ^^^^ + ^ ⋅ ^^^^^ ^ ^ ^ ^^ = 2^ ⋅ ^^^^ + ^^^^With ^ the elongation which is greater than 1 in the case of an elongation of the garment 100 and which is less than 1 in the case of a retraction of the garment 100. The lengths ^^^^, ^^^^ and ^^^^ may be predetermined in an image comprising the garment 100 at rest, the strip 101 and the lines 102 previously acquired. They may also be predetermined by prior measurements by measuring means such as a tape measure. Thus, there remains only one unknown which corresponds to the elongation ^ which is expressed, from the cross-ratio, in the following manner which is a second-degree equation.^^^ + ^^ + ^ = 0With ^, ^ and ^ real-valued coefficients. Since all the lengths in the cross-ratio are known, then the coefficients ^, ^ and ^ are also known. Thus, by solving the second degree equation, it is possible to express the elongation ^ as a function of the coefficients ^, ^ and ^.It is therefore possible to obtain a value of the elongation ^. According to a numerical example, it is considered that the lengths ^^^^, ^^^^ and ^^^^ measured are the following:^^^^ = ^^^^ = 5 ^^^^^^ = 4 ^^the expression of the lengths ^. ^ ^ ^ ^ ^ , ^ ^ ^ ^ ^ ^, ^^ ^ ^ ^ ^ and ^ ^ ^ ^ ^ ^ become in the example:^ ^ ^ ^ ^ ^ = 5 ⋅ ^ + 4^ ^ ^ ^ ^^ = 4 + 5 ⋅ ^^ ^ ^ ^ ^ ^ = 2 ⋅ 5 ⋅ ^ + 4 = 10 ⋅ ^ + 4with ^ ^ ^ ^ ^ ^ ^ , ^ ^ ^ ^ ^, ^^ ^ ^ ^ ^ and ^ ^ ^ ^ ^ ^ in mm. Furthermore, in the numerical example, it is considered that the lengths , ^^ ^^ ^ ^ ^^ and ^^ ^^ ^^^ ^are as follows:^ ^ ^^ ^ ^^ ^ = 30 ^^^^^^^ ^ ^^ ^ ^^ ^ = 10 ^^^^^^^ ^ ^^ ^ ^^ ^ = 20 ^^^^^^Thus, the expression for the cross-ratio equality in expanded form is as follows. 30 + 10 10 + 20 5 ⋅ ^ + 4 4 + 5 ⋅ ^× 30 + 10 = × 10 + 20410 ⋅ ^ + 4The following quadratic equation is deduced. 25 ⋅ ^^ − 40 ⋅ ^ − 16 = 0After solving the quadratic equation, the elongation ^ is equal to 1.93. The elongation is much greater than 1 and therefore corresponds to an elongation of the garment 100. Of course, a similar reasoning can be applied for the embodiments illustrated in Figure 2b, Figure 2c and Figure 2d. The reasoning can also be applied beyond the compression garment 100, for any object that obeys Hooke's law. Indeed, the elongation ^ is expressed from an analysis of an image, predetermined measurements and the expression of the cross-ratio. Moreover, the expression of the cross-ratio and the assumption of uniform deformation remain valid as long as the object obeys Hooke's law. Therefore, the reasoning remains valid for any set that includes an object, a frame and an imprint that is undeformable relative to the frame.In a case where several lines 102 are superimposed in the image, a plurality of intermediate elongations ^. ^are determined according to the same reasoning then the elongation ^ is obtained by averaging the plurality of intermediate elongations ^^. In the case of several segments, the elongation ^ is determined for each segment. During a step E3, a circumference 301 of the deformed garment 100 is determined from the elongation ^ and a circumference of the garment at rest predetermined in an image of the garment 100 at rest or by measuring means such as a tape measure. Indeed, by assuming that the elongation is distributed uniformly in the garment, the circumference of the deformed garment is proportional to the circumference of the garment at rest. It is therefore possible to obtain the circumference of the deformed garment by multiplying the circumference of the garment at rest by the elongation. In the digital example, it is considered that the circumference of the garment at rest is 100 mm, then the circumference of the deformed garment is 193 mm.In the case where several segments are in the image, then a circumference of the deformed garment 100 is determined for each segment. It is thus possible to repeat steps E1 to E3 from a first end of the garment to a second opposite end of the support garment to obtain a surface 30 of the deformed support garment by concatenation of the circumferences 301. During a step E4, a volume 401 of the deformed garment 100 is determined from the circumference 301. A pressure field 402 applied to the deformed garment 100 is also determined from the circumference 301 independently of the determined volume 401.For example, each point of the pressure field 402 can be determined by applying Laplace's law in which the pressure at each point of the deformed garment 100 is equal to the ratio between a tension of the garment, defined as the product of the Young's modulus of the garment, given by the manufacturer or obtained by tensile testing, and the deformation of the garment deduced from the measurements obtained by implementing steps E1 to E2, and the radius of the circumference obtained in step E3. Assuming a uniform distribution of the Young's modulus in the garment, it is further possible to determine a normalized pressure field, for example expressed between zero as the lowest measured value and one as the highest measured value, by choosing the Young's modulus to be equal to one because the tension is proportional to the elongation.It is thus possible to repeat steps E1 to E4 from the first end of the garment to the second opposite end of the compression garment to obtain a volume and a total pressure field 40 of the compression garment deformed by concatenation of the volumes 401 and the pressure fields 402. Furthermore, the circumferences 301, the surface 30, the volumes 401, the pressure fields 402, the volume and the total pressure field 40 determined can further be displayed on a screen of the terminal 11. In order to improve the calculation speed, the database can be configured to measure the elongation of the compression garment 100 from the image by implementing steps E11 to E2 and then transmitting the results to the terminal 11 for display. Numerous modifications can be made to the device and the method without departing from the scope of the description.

Claims

CLAIMS 1. Procédé mis en œuvre par ordinateur de mesure d’un allongement d’un objet (100), le procédé comprenant les étapes suivantes : acquisition d’une image (E1) comprenant un objet (100) en position déformée et une empreinte (101) reliée à l’objet (100), l’empreinte (101) étant indéformable par rapport à l’objet (100), l’objet (100) comprenant un repère (102) ; et à partir de l’image acquise et de dimensions de l’objet (100) au repos, détermination (E2) d’un allongement (^) de l’objet (100) par un suivi du repère (102) de l’objet (100) par rapport à l’empreinte (101), les dimensions de l’objet (100) au repos étant définies par rapport au repère (102) et par rapport à l’empreinte (101).

2. Procédé selon la revendication 1, comprenant une détermination (E13) d’un segment dans the image, the determination of the elongation (^) of the object taking place in the segment.

3. Procédé selon la revendication 2, dans lequel l’empreinte comprend deux marqueurs (103), le segment étant défini entre les deux marqueurs (103).

4. Procédé selon la revendication 3, dans lequel les deux marqueurs (103) sont des fiducial markers, barcodes, or QR codes.

5. Procédé selon l’une des revendications 1 à 4, comprenant une étape de mesure (E3), à partir de l’allongement (^), d’une dimension de l’objet (100).

6. Procédé selon l’une des revendications 1 à 5, comprenant les étapes suivantes : à partir de l’allongement (^), mesure (E3) d’une circonférence de l’objet (100) ; et à partir de la mesure, détermination (E4) d’un volume de l’objet (100).

7. Procédé selon l’une des revendications 1 à 6, dans lequel l’empreinte comprend deux motifs reliés distinctement sur l’objet (100).

8. Procédé selon l’une des revendications 1 à 6, le procédé étant mis en œuvre par un terminal (11) et dans lequel l’objet (100) est un vêtement de contention, le repère (102) est formé de deux lignes et l’empreinte (101) est formée d’une bande.

9. Procédé selon la revendication 8, dans lequel la bande (101) est entre les deux lignes (102), or the two lines (102) are adjacent.

10. Procédé selon la revendication 8, dans lequel l’empreinte (101) est formée d’une première bande (101a) et d’une deuxième bande (101b), une première ligne étant prise sur une extrémité de la première bande et une deuxième ligne étant prise sur une extrémité de la deuxième bande (101b) en regard de l’extrémité de la première bande (101a).

11. Procédé selon l’une des revendications 8 à 10, dans lequel la bande comprend des marqueurs (103), les marqueurs étant alignés sur la bande.

12. Ensemble (10) comprenant : un objet (100) comprenant un repère (102) ; et une empreinte (101) reliée à l’objet (100), l’empreinte (101) étant indéformable par rapport à l’objet (100), l’ensemble étant configuré pour permettre une détermination d’un allongement (^) de l’objet (100) par un suivi d’un repère de l’objet (100) par rapport à l’empreinte.

13. Dispositif (1) de mesure d’une déformation d’un objet, le dispositif comprenant : un ensemble (10) comprenant : un objet (100) comprenant un repère (102) ; et une empreinte (101) reliée à l’objet (100), l’empreinte (101) étant indéformable par rapport à l’objet (100), l’ensemble étant configuré pour déterminer un allongement (^) de l’objet (100) par un suivi d’un repère (102) de l’objet (100) par rapport à l’empreinte (101) ; et un terminal (11) configuré pour : acquérir une image comprenant l’ensemble (10) ; et à partir de l’image acquise et de dimensions de l’objet au repos, déterminer un allongement (^) de l’objet (100) par un suivi du repère (102) de l’objet (100) par rapport à l’empreinte (101), les dimensions de l’objet (100) au repos étant définies par rapport au repère (102) et par rapport à l’empreinte (101).

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