Method for calibrating colors between the real world and the virtual world

Abstract

The invention relates to a computer-implemented color calibration method, the method comprising: the selection of a real body area sample (3), in particular hair, colored by a real reference target color (31), each real sample being associated with a real identifier; the visual determination, by an expert, of the real reference target color (31); the reception, by a computer color management system, of one or more inputs (5) indicative of the real reference target color (31); and the storage, by the computer color management system, of an updated virtual color profile. Figure 1

Description

Title of the invention: Method for calibrating colors between the real world and the virtual world

[0001] The present invention relates to a computer-implemented method for calibrating the colors of a screen based on the observation of colors in real-world mode. It also relates to the use of such a calibrated screen to reproduce and visualize, in the virtual world, a color applied in the real world to a body area, particularly to hair.

[0002] More generally, a cosmetic product is a product as defined in Regulation (EC) No 1223 / 2009 of the European Parliament and of the Council of 30 November 2009 on cosmetic products.

[0003] The body area may be the skin, lips, eyelashes, eyebrows, nails and especially the hair. Technological background

[0004] While our eye is a wonderful partner in showing us the world, it is unfortunately quite incapable of helping us calibrate a graphics chain. However, good color management between a photograph of an object displayed on a screen and the real object can only be achieved if the screen is calibrated.

[0005] All color management is centered on this step: calibration. It is thanks to the calibration of the different devices and the knowledge of colorimetric characteristics that it will be possible to virtually reproduce the color closest to the real color.

[0006] The purpose of calibration and then characterization is to know precisely the colorimetric characteristics of a given device or, to put it figuratively, how the different devices "distort" colors - what colors they "see" for a given signal - in order to be able to "correct" them afterwards and what colors they are able to reproduce.

[0007] For example, we know of ICC profile creation software sold with probes and other colorimeters which compare a coloured target whose characteristics are precisely known, that is to say the one and only colour L*a*b* of a coloured sample, to the colour actually printed by default by a printer, at the exact wavelength of RGB displayed on the screen.

[0008] US patent 9924778B2 discloses an apparatus for measuring the optical properties of skin, comprising:

[0009] a spectrometer and a light source under the control of a processing circuit;

[0010] an optical cavity in which illumination from the light source is provided, the cavity having an opening to illuminate a part of the skin to be measured;

[0011] a calibration / normalization reference having a surface to be positioned such that the opening illuminates the calibration / normalization reference;

[0012] a storage circuit coupled to the processing circuit which stores linearization coefficients and spectral data for the calibration / normalization reference and stores data for a classifier prediction algorithm;

[0013] a display under the control of the processing circuit; and

[0014] a wireless module under the control of the processing circuit;

[0015] the processing circuit controls the display of control information on the display;

[0016] In response to user activation based on the displayed command information, a measurement of the calibration / normalization reference is performed and stored in the storage circuit.

[0017] Patent EP2661222B1 discloses a system for analyzing at least one skin characteristic by means of optics and computer image processing, in particular for detecting skin cancer or for proposing at least one product suitable for the skin and / or hair, comprising:

[0018] a consumer electronic device, comprising a lens, capable of acquiring at least one image by digital means and capable of producing data relating to said at least one acquired image; and characterized in that it comprises:

[0019] specific means, distinct from said consumer electronic device (4) for producing an optical magnification of the image capable of analyzing at least one skin characteristic; and

[0020] means for introducing at least one piece of information into the image, these means being included in said specific means for achieving optical magnification of the image; and

[0021] means for processing said data in relation to said at least one image acquired for the purpose of producing information relating to at least one skin characteristic,

[0022] said specific means for producing an optical magnification of the image further include means for calibrating at least one characteristic of the image.

[0023] However, the calibration and visualization methods known to date can still be improved from the point of view of their real-world reliability.

[0024] The problem posed by the invention is to provide a system enabling:

[0025] To digitally visualize all possible colorings, particularly hair colorings, so that the user can visualize the result of a coloring on different media, including but not limited to straight and curly media, i.e. in particular more or less straight hair and more or less wavy hair (i.e. (on the whole head, or in simple samples);

[0026] To explore different colors on a support by starting with a selected color and adjusting it to achieve the desired result by selecting different parameters (ash, gold, matte etc);

[0027] To link each digital color visualization to a result characterized in the real world via standard measurements (such as Lab values, brightness or other) to link the two worlds;

[0028] To propose a color formula that produces the desired color on a given substrate;

[0029] To reproduce any color of a body area, in particular hair in real life on a calibrated screen by providing an accurate digital representation that can be adjusted to obtain any desired color;

[0030] To predict the result of a coloring on different substrates, in particular on hair. Definition of the invention

[0031] The invention relates to a computer-implemented color calibration method, the method comprising:

[0032] the selection of a real sample of body area, in particular hair, colored by a real target reference color, each real sample being associated with a real identifier,

[0033] the visual determination, by an expert, of the actual target reference colour;

[0034] the reception, by a computer color management system, of one or more indicative inputs of the actual target reference color;

[0035] the display on a screen, by the color management computer system, of a virtual image of the body area colored by a digital reference color determined by the color management computer system in response to the indicative inputs of the actual reference color;

[0036] the storage, by the color management computer system, of an updated virtual color profile comprising the real identifier and the virtual image of the body area colored by the digital reference color obtained in response to the indicative inputs of the real reference color, in order to match the appearance between the virtual image and the real sample (or calibrate the appearance between the virtual image and the real sample taking into account the color profile of the screen).

[0037] Thanks to the integration of advanced rendering algorithms and meticulous color mapping, the system ensures that every color of a virtually rendered body area, including hair, aligns with the real world. By leveraging real-time 3D rendering capabilities, the method makes it possible to obtain physically accurate results. realistic, setting a new standard for hair color representation. The ability to instantly and seamlessly visualize and reproduce every color of a body area, including hair in real life on a calibrated screen, opens up new possibilities in various industries, such as beauty, fashion, and entertainment, offering a truly immersive and realistic digital experience.

[0038] Thanks to the invention, it is now possible to instantly visualize and reproduce each hair color in real life on a calibrated screen equipped with an appropriate expert interpretation user interface.

[0039] The invention also relates to a computer-readable medium comprising instructions which, when executed by a computer, cause the computer to execute the process as described above.

[0040] The invention also relates to a computer program product comprising instructions which, when the program is executed by a computer, cause the computer to

[0041] the reception, by a computer color management system, of one or more indicative inputs of an actual target reference color;

[0042] the display on a screen, by a computer color management system, of a virtual image of the body area colored by a digital reference color, in response to indicative inputs of the actual reference color;

[0043] the storage, by the color management computer system, of an updated virtual color profile comprising the real identifier and the virtual image of the body area colored by a digital reference color, obtained in response to indicative inputs of the real reference color, in order to match the appearance between the virtual image and the real sample.

[0044] The invention also relates to a data processing system comprising:

[0045] a memory in which a plurality of virtual reference images associated with virtual digital reference parameters are stored,

[0046] a processing unit configured to implement the computer program product as defined above,

[0047] a screen configured to display virtual reference images, optionally associated with virtual digital reference parameters,

[0048] a storage unit configured to store an updated virtual color profile.

[0049] The invention also relates to a screen calibrated by a system as described above.

[0050] The invention also relates to the use of the screen as described above, to predict the result of a coloring from a three-dimensional virtual rendering of hair.

[0051] The invention also relates to the use of the screen as described above, to recommend a colour on a body area.

[0052] The invention also relates to the use of the screen as described above, to align interactively with a person on a desired colour and, possibly, associate a cosmetic composition with the desired colour.

[0053] The invention also relates to the use of the screen as described above, for a virtual fitting in photo or video.

[0054] The invention also relates to the use of the screen as described above, to display a virtual half-head section and compare live the result of two colorings.

[0055] The present invention introduces an advanced technique that leverages the power of a state-of-the-art, real-time 3D rendering product to accurately characterize the vast color space of a body area, particularly hair, present in the real world. By collecting a diverse dataset including actual samples of a body area, particularly hair, whether obtained from a medium, such as real or synthetic hair, the proposed method enables expert analysis and mapping of hair color information onto a digital representation.

[0056] From a limited number of samples from a body area, in particular carefully selected hair, the process constructs a colorimetric space model, and this model allows an instant and transparent visualization of any hair color in real life on a properly calibrated screen.

[0057] The method for constructing an interactive 3D model according to the invention comprises three components:

[0058] 1) A realistic 3D rendering of hair in real time

[0059] State-of-the-art technologies use physics-based rendering techniques to accurately simulate light diffusion, light absorption, reflection and transmission in media, including strands of hair of various types, ensuring that the rendered hair looks visually convincing and exhibits realistic shades, shadows and highlights.

[0060] 2) A synthesis and mapping of expertise

[0061] The characterization of the physical color space of a body area, in particular of hair, makes it possible to ensure the correspondence between a real hair color and its digital representation.

[0062] 3) Construction of a color space model through samples of data validated by expert physical-visual experiments. Preferred modes of implementation

[0063] Preferably, the method according to the invention has one or more of the following characteristics, taken alone or in combination:

[0064] The virtual reference image is obtained from a realistic real-time 3D rendering of the colored body area, by "path tracing" or "ray tracing" or "inverse rendering" or generative AI or diffusion AI;

[0065] Each indicative input of the actual reference color is associated with the virtual reference image by modeling a color space;

[0066] The digital color of the virtual reference image can be modified with color space levers, in particular CIELAB, or by intrinsic 3D rendering levers;

[0067] The indicative entries for the actual reference colour include expert language, including gloss, tone height, ash, iridescence, gold, copper, virtual mahogany, red and matte;

[0068] The expert varies the digital colors of virtual reference images until a visual match is obtained between a virtual digital reference color and the real target reference color, using an interface that has levers to vary the colors.

[0069] The expert records indicative inputs of the actual target reference colour suitable for defining the body area, such as dimensions, hue, quality, hair flexibility, skin or hair type.

[0070] The process is repeated for several real samples of colored body area with a real reference target color, in order to match the appearance between the virtual image and the real sample for a full range of colors. Description of the figures

[0071] Other features and advantages of the invention will become apparent from the following detailed description, non-limiting examples of its implementation, and from examination of the accompanying schematic and partial drawing, in which: Description of Figures

[0072] [Fig.1]

[0073] Fig. 1 represents a display unit presenting a virtual reference image and virtual reference digital parameters, before determining the reference 3D rendering associated with the actual strand according to Fig. 2.

[0074] [Fig.2]

[0075] Figure [Fig. 2] represents a real lock of hair,

[0076] [Fig.3]

[0077] Figure 3 represents a 3D model in Lab space,

[0078] [Fig.4]

[0079] Figure [Fig. 4] represents a tetrahedron associated with a point of the 3D model of Figure [Fig. 3],

[0080] [Fig.5]

[0081] Figure 5 represents a color chart in the real world,

[0082] [Fig.6]

[0083] Figure 6 represents a list of expert concepts on the user interface,

[0084] [Fig.7]

[0085] Figure 7 represents a target photograph in the real world,

[0086] [Fig. 8]

[0087] Figure 8 represents a user interface after selection of a reference 3D rendering associated with the actual wick according to Figure 2.

[0088] [Fig.9]

[0089] Figure [Fig. 9] represents a block diagram of the process according to the invention.

[0090] In order to obtain accurate color replication, a first step consists of establishing a connection between the real world 1 and the virtual world 2, that is, between the domain of digital colors and the domain of physical colors. To do this, synthetic or real hair strands 3 that simulate real hair colors 31 are used as tangible references for hair coloring in the real world 1.

[0091] In the real world 1, a strand of hair 3, on which a real target color 31 has been applied, is placed on a support 40.

[0092] Figure 2 shows such a wick 3 carefully arranged in a predefined environment, subjected to predetermined lighting conditions. In the example shown, each wick 3 of actual target color 31 is suspended from a support 40 placed in the interior space of a closed box 41, one front side wall 42 of which is transparent so that the wick 3 is visible to an expert.

[0093] 3D Rendering

[0094] In [Fig.1], a display unit 4 displays a virtual reference image 21 of colored hair (or 3D rendering) having a digital reference color 22. The unit 4 further presents virtual digital reference parameters 5 in relation to each virtual reference image 21. The virtual digital reference parameters 5 are the user-selectable menu entries.

[0095] In practice, the expert modulates the digital reference color 22 of the virtual reference image 21 (3D rendering) by modifying the virtual reference parameters 5, until a visual match is obtained with the actual target color 31 of the strand 3.

[0096] As illustrated in [Fig.3], a 3D model is constructed in the CIELAB color space, based on calibrated hair color references.

[0097] As a reminder, the CIE Lab 1976 color space, generally called CIELAB, is a color space particularly used for characterizing surface colors. Three quantities characterize colors: lightness L, derived from the surface luminance; and two parameters a and b that express the difference between the color and that of a gray surface of the same lightness. The existence of a gray, uncolored, achromatic surface implies explicitly stating the composition of the light illuminating the colored surface.

[0098] The parameters of the Lab system are:

[0099] the brightness L takes values ​​between 0 (black) and 100 (reference white);

[0100] the parameter a represents the value on an axis going from green to red;

[0101] The parameter b represents the value on an axis ranging from blue to yellow.

[0102] In the example shown, the 3D model defines nodes 35, 36, 37, 38, 39, with segments indicating the distance between colors digitally calibrated according to LAB values.

[0103] The 3D model is transformed, for example, into a 3D Delaunay triangulation (tetrahedralization), where each tetrahedron (A, B, C, D) is composed of four shades ([Fig. 4]), which makes it possible to obtain the LAB value of any point. Because the color of each strand in shade guide 7 of [Fig. 5] has been calibrated, as evidenced by the hair rendering images of [Fig. 1], it is possible to generate any desired hair color in real time by exploiting this 3D model of the CIELAB color space. The tetrahedron 46 of [Fig. 4] is associated with any point 45 of the 3D model.

[0104] In [Fig. 5], a color chart 7 has been schematically represented without showing the shades but in reality, all the hair colors in the color chart are represented with shades that are more or less dark or colored.

[0105] Several libraries exist for triangulation, such as CGAL.

[0106] For each node 35, 36, 37, 38, 39 in the 3D space, its Lab value was measured (it can be measured in any other color or appearance space; CIELAB was used for simplicity). Navigation within this color space can be performed directly via the Lab values.

[0107] To be more concrete, this 3D space is translated into expert notions in the field of hair color, by introducing "semantic" orientations into this colorimetric space, such as different dimensions like:

[0108] Shade of color ranging from darkest to lightest,

[0109] Copper ranging from the most coppery to the least coppery,

[0110] Gold ranging from the most golden to the least golden.

[0111] We can then move along these dimensional axes of semantic orientations, instead of using Lab values, which is more intuitive for the end user.

[0112] Figure 6 represents a user interface offering examples of concepts experts in connection with the 3D space represented in [Fig.3].

[0113] In [Fig. 7], a photograph 32 is shown depicting hair 3 with a new shade constituting a real target color 31. This photograph could, for example, be a selfie or an image captured from the internet. The photograph could be replaced by a textual description. In the example shown, the hair is wavy.

[0114] An expert searches in the color chart of real colors 7, for a real color 310 which visually corresponds best to the color 31 of the target represented by the hair 3.

[0115] On [Fig.8], a color approximately close to the color 31 of the target 3 is displayed on the screen, then the expert refines the color until the desired and visually satisfying shade closest to the actual target color 31 is obtained, by modulating the expert notions 5, until the desired color 310 is obtained.

[0116] Figure 9 illustrates the process according to the invention by means of a block diagram.

[0117] To calibrate the colors in the virtual world 2, a real hair sample 3, to which a real target color 31 has been applied, is provided in the real world 1 shown on the right of [Fig. 9]. This real sample 3 is placed under predetermined lighting and spatial placement conditions. In the virtual world 2 shown on the left of [Fig. 9], a display unit 4 is provided for displaying a plurality of virtual reference images 21 of hair colored with a digital reference color 22. These virtual reference images 21 are 3D renderings. The unit 4 initially presents virtual digital reference parameters 5 related to each rendering 21.

[0118] An expert selects, from among the plurality of reference virtual images 21, the reference virtual image 210 presenting the reference digital color 220 which is visually closest to the real target color 31 and which constitutes the selected reference rendering 220.

[0119] The selected reference rendering 220 undergoes a transformation 8 comprising the determination 9 of a 3D model from the selected rendering 200 and an interpolation 10 of the 3D model, in order to determine the virtual numerical parameters 50 associated with the selected reference rendering 220.

[0120] The invention is not limited to the illustrated embodiments. Other presentations of the display are in particular part of the present invention. Those skilled in the art will understand that the embodiments described above can be combined to form new embodiments provided they are technically compatible.

Claims

Demands

1. A computer-implemented color calibration method, the method comprising: selecting a real sample of body area (3), in particular hair, colored by a real target reference color (31), each real sample being associated with a real identifier; visually determining, by an expert, the real target reference color (31); receiving, by a computer color management system, one or more inputs (5) indicative of the real target reference color (31); displaying on a screen (4), by the computer color management system, a virtual image (21) of the body area (3) colored by a digital reference color (22) determined by the computer color management system in response to the indicative inputs of the real reference color (31);the storage, by the color management computer system, of an updated virtual color profile comprising the real identifier and the virtual image (21) of the body area colored by the digital reference color (22) obtained in response to the inputs (5) indicative of the real reference color (31), in order to match the appearance between the virtual image (21) and the real sample (3).

2. A computer-implemented method according to claim 1, characterized in that the virtual reference image (21) is obtained from a realistic real-time 3D rendering of the colored body area, by "path tracing" or "ray tracing" or "inverse rendering" or generative AI or diffusion AI.

3. A computer-implemented method according to any one of the preceding claims, characterized in that each input (5) indicative of the actual reference color is associated with the virtual reference image (21) by modeling a color space.

4. A computer-implemented method according to any one of claims 2 or 3, characterized in that the digital color (22) of the virtual reference image (21) is modifiable with color space levers, in particular CIELAB, or by intrinsic 3D rendering levers.

5. A computer-implemented method according to any one of the preceding claims, characterized in that the indicative inputs of the actual reference color (5) include expert language, including gloss, tone height, ash, iridescence, gold, copper, virtual mahogany, red, and matte.

6. A computer-implemented method according to any one of the preceding claims, characterized in that the expert varies the digital colors (22) of virtual reference images (21) until a visual match is obtained between a virtual digital reference color (21) and the actual target reference color (31), using an interface that has levers to vary the colors.

7. A computer-implemented method according to any one of the preceding claims, characterized in that the expert records inputs (5) indicative of the actual target reference color (31) capable of defining the body area (3), such as dimensions, hue, quality, hair suppleness, skin or hair type.

8. A computer-implemented method according to any one of the preceding claims, characterized in that it is repeated for several real samples of body area (3) colored by a real reference target color (31), in order to match the appearance between the virtual image (21) and the real sample (3) for a full range of colors.

9. Computer-readable medium comprising instructions which, when executed by a computer, cause the computer to perform the process according to any one of the preceding claims.

10. Product: A computer program comprising instructions which, when the program is executed by a computer, cause the computer to: receive, by a computer color management system, one or more inputs (5) indicating an actual target reference color (31); display on a screen (4), by a computer color management system, a virtual image (21) of the body area (3) colored by a digital reference color (22), in response to the inputs indicating the actual reference color (31); store, by the computer color management system, a updated virtual color profile including the real identifier and virtual image (21) of the body area colored by a digital reference color (22), obtained in response to the inputs (5) indicative of the real reference color (31), in order to match the appearance between the virtual image (21) and the real sample (3).

11. Data processing system comprising: a memory in which is stored a plurality of virtual reference images (21) associated with virtual digital reference parameters, a processing unit configured to implement the computer program product according to the preceding claim, a screen configured to display virtual reference images (21), optionally associated with virtual digital reference parameters (5), a storage unit configured to store an updated virtual color profile.

12.

13. A screen calibrated by a system according to the preceding claim. Use of a screen calibrated according to claim 12, to predict the result of a coloring from a three-dimensional virtual rendering of hair (21).

14. Use of a screen calibrated according to claim 12, to recommend a colour on a body area (3).

15. Use of a screen calibrated according to claim 12, to interactively align with a person on a desired color and, optionally, associate a cosmetic composition with the desired color.

16. Use of a screen calibrated according to claim 12, for virtual fitting in photo or video.

17. Use of a screen calibrated according to claim 12, to display a virtual half-head section and compare live the result of two colorings.