FR 3102629 A1 20210430 FR 1911981 A 20191025 The invention is related to a method for managing image data in an automotive lighting device (10) and comprises the steps of providing the lighting module with a reference image pattern (1) and a further image pattern (2). Then, the control unit (6) calculates an alternative dataset (3) with a data number lower than the number of pixels of the further image pattern and sends the alternative dataset (3) to the light module (4). Then, the light module (4) calculates a correction pattern (30), which is related to the alternative dataset (3) and the reference image pattern (1) and calculates a projection pattern from the reference image pattern (1) and the correction pattern (30). Figure pour l’abrégé : Figure 5 Method for managing image data and automotive lighting device This invention is related to the field of automotive lighting devices, and more particularly, to the management of the electronic data derived from the control of the lighting sources. Current lighting devices comprises an increasing number of light sources which has to be controlled, to provide adaptive lighting functionalities. This number of light sources involves a big amount of data, which has to be managed by the control unit. The CAN protocol is often used, in some of their variants (CAN-FD is one of the most used ones) to transfer data between the PCM and the light module. However, some car manufacturers decide to limit the bandwidth of the CAN protocol, and this affects the management operations, which usually requires about 5 Mbps. Current compression methods are not very efficient for high beam patterns, and this compromises the bandwidth reduction which is requested by car manufacturers. Further, there are so-called “lossy methods”, which increase the compression rate but at the expense of generating data errors. These errors are sometimes negligible, but other times they turn out to be important. A solution for this problem is sought. The invention provides a solution for these problems by means of a method for managing image data according to claim 1 and an automotive lighting device according to claim 7. Preferred embodiments of the invention are defined in dependent claims. Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art. It will be further understood that terms in common usage should also be interpreted as is customary in the relevant art and not in an idealised or overly formal sense unless expressly so defined herein. In this text, the term “comprises” and its derivations (such as “comprising”, etc.) should not be understood in an excluding sense, that is, these terms should not be interpreted as excluding the possibility that what is described and defined may include further elements, steps, etc. In a first inventive aspect, the invention provides a method for managing image data in an automotive lighting device, wherein the automotive lighting device comprises a control unit and a lighting module, the method comprising the steps of - the control unit provides the lighting module with a reference image pattern comprising a plurality of pixels, wherein each pixel is characterized by a value related to the luminous intensity of the pixel; - the control unit provides a further image pattern, comprising a plurality of pixels, wherein each pixel is characterized by a value related to the luminous intensity of the pixel; - the control unit calculates an alternative dataset with a data number lower than the number of pixels of the further image pattern, wherein the alternative dataset is related to the values of luminous intensity of the pixels, - the control unit sends the alternative dataset to the light module - the light module calculates a correction pattern, which is related to the alternative dataset and the reference image pattern; and - the light module calculates a projection pattern from the reference image pattern and the correction pattern. This method is aimed to manage the image data which is exchanged between a control unit and a light module. The control unit is in charge of calculating the reference image pattern, each further image pattern and the corresponding alternative dataset and correction pattern, and may be located in any position of the automotive vehicle, not necessarily physically inside the lighting device. The lighting module is aimed to provide a projection pattern, either for lighting or signalling, and is located inside the lighting device. The main advantage of this method is the increasing in the compression rate but without losing data. The first reference image is considered as containing the correct initial values, and the correction pattern, which is easier to compress than the further image pattern, is enough for the light module to calculate, thanks to the reference image pattern, the correct version of the further image pattern. This is extremely useful in the cases of ADB (Adaptive Driving Beam) or DBL (Dynamic Bending Light), where the difference between a frame and the next frame is low. Sometimes, the requirement of compressing the images is not necessary, due to the fact that the alternative dataset size is small enough to be transmitted without being compressed. In any case, data bandwidth is saved and no error is present in the pixels due to the provision of the reference image pattern. In some particular embodiments, the method further comprises the step of buffering the reference image pattern in the light module. When the reference image pattern is buffered, taking advantage of the abilities of modern light modules, it is easy to prepare the further projection patterns based on the correction patterns which are being provided. In some particular embodiments, the light pixels of the reference image pattern and the light pixels of the further image pattern are greyscale pixels, and more particularly, the luminous intensity of each pixel is characterized by a number according to a scale from 0 to 255. Light modules usually define the light pattern on a grey scale, where the luminous intensity is graded from 0 to 255. This is a way of quantifying the light pattern so that it becomes able to be converted into light data, and then transmitted and managed by the control unit of the vehicle. In some particular embodiments, the alternative dataset is obtained by selecting strings of pixels of the further image pattern and replace each string of pixels by a linear approximation. In some particular embodiments, the correction pattern is obtained by dividing the value of a pixel of the alternative dataset by the value of the corresponding pixel of the reference image pattern, and the projection pattern is calculated by multiplying the value of the reference image pattern by the corresponding value of the correction pattern. This operation is easy to perform, and means an advantageous step, especially in the cases of ADB (Adaptive Driving Beam), when the values are fixed and only a groups of zeros means the difference between the reference image and the further image patterns. In some particular embodiments, the method further comprises the steps of - compressing at least a portion of the correction pattern before sending it to the light module, thus creating a compressed data; and - decompressing the compressed data by the light module. Sometimes it is advisable to compress the data, so that the bandwidth is reduced even more. In a second inventive aspect, the invention provides a lighting device comprising - a light module comprising a plurality of light sources; and - a control unit to carry out the steps of a method according to the first inventive aspect. This lighting device is able to operate with a lower bandwidth than the traditional ones, and without losing information. In some particular embodiments, the light module further comprises a processor unit, the processor unit being configured to calculate the correction pattern and decompress the compressed data. With a decompression stage in the proper light module, the bandwidth is narrowed until the module itself. In some particular embodiments, at least the processor unit comprises an image buffer to keep the first image. This way, the advantageous features of modern light modules are considered to improve the method of the invention. In some particular embodiments, the light sources are solid-state light sources, such as LEDs.The term "solid state" refers to light emitted by solid-state electroluminescence, which uses semiconductors to convert electricity into light. Compared to incandescent lighting, solid state lighting creates visible light with reduced heat generation and less energy dissipation. The typically small mass of a solid-state electronic lighting device provides for greater resistance to shock and vibration compared to brittle glass tubes/bulbs and long, thin filament wires. They also eliminate filament evaporation, potentially increasing the life span of the illumination device. Some examples of these types of lighting comprise semiconductor light-emitting diodes (LEDs), organic light-emitting diodes (OLED), or polymer light-emitting diodes (PLED) as sources of illumination rather than electrical filaments, plasma or gas. To complete the description and in order to provide for a better understanding of the invention, a set of drawings is provided. Said drawings form an integral part of the description and illustrate an embodiment of the invention, which should not be interpreted as restricting the scope of the invention, but just as an example of how the invention can be carried out. The drawings comprise the following figures: shows a first image of the photometry of a high beam module which is projected by an automotive lighting device according to the invention. shows a portion of a reference image pattern representing the photometry of [Fig 1]. shows a portion of a further image pattern, which corresponds to a second image of an embodiment of a method according to the invention. shows a portion of a pattern corresponding to an alternative dataset, which corresponds to an intermediate image of an embodiment of a method according to the invention. shows a portion of a coefficient pattern, which corresponds to an intermediate image of an embodiment of a method according to the invention. shows an automotive lighting device according to the invention. Elements of the example embodiments are consistently denoted by the same reference numerals throughout the drawings and detailed description where appropriate: 1 First image pattern 11 Pixel of the first image pattern 2 Further image pattern 21 Pixel of the second image pattern 3 Alternative dataset 30 Coefficient pattern 4 Light module 5 LEDs 6 Control unit 7 Processor unit 10 Automotive lighting device 100 Automotive vehicle The example embodiments are described in sufficient detail to enable those of ordinary skill in the art to embody and implement the systems and processes herein described. It is important to understand that embodiments can be provided in many alternate forms and should not be construed as limited to the examples set forth herein. Accordingly, while embodiment can be modified in various ways and take on various alternative forms, specific embodiments thereof are shown in the drawings and described in detail below as examples. There is no intent to limit to the particular forms disclosed. On the contrary, all modifications, equivalents, and alternatives falling within the scope of the appended claims should be included. shows a first image of the photometry of a high beam module which is to be projected by an automotive lighting device according to the invention. This first image may be divided into pixels and each pixel may be characterized by its luminous intensity, in a scale from 0, which would correspond to black, to 255, which would correspond to white. shows a portion of such a pixel matrix, called reference image pattern 1. Each pixel 11 of this reference image pattern 1 is characterized by a number according to the aforementioned scale. The compression of this reference image pattern 1 according to commercially available softwares would offer a compression rate lower than 50%, which is unacceptable by some car manufacturers. This reference image pattern 1 is sent to a light module, to be buffered. The importance of this step will be understood later. shows a portion of a further image pattern 2, which is calculated by the control unit and intended to be projected by the light module. It is similar to the one of [Fig 2], but with a group of zeros located in pixel 21 positions, which form a dark tunnel to be used in ADB. This figure just tries to represent an example of this method. For the sake of clarity, no real matrices are used, since they would be too large and complex. A simplification is used so that the method of the invention is clearly understood. If this further image pattern was to be compressed and sent directly to the light module, the compression rate would not be high enough to obtain an acceptable bandwidth. In this invention, instead of sending the further image pattern 2, a first lossy method is then applied to the further image pattern 2. These methods replace some strings of values of luminous intensity by a smaller amount of data, which represent the luminous evolution in this string. For example, a group of 20 values may be replaced by a linear approximation, to save data size. The linear approximation will not usually be identical to the original values, but in some cases will provide a valid approximation, with a low error, and a significant data size saving. The higher the compression rate achieved, the higher the maximum error obtained. An example of this alternative dataset 3 is shown in . In this case, the light values of the further image pattern 2 are replaced by linear approximations. The data for these approximations are sent to the light module, either compressed or not, depending on the data size and the car manufacturer’s requirements. The alternative dataset 3 is sent to the light module instead of the actual further image pattern 2. The light module receives this alternative dataset, but does not project it, since it has some errors, due to the approximations which have been carried out to save bandwidth. Instead, the light module calculates a coefficient pattern 30, shown in . Each pixel of this coefficient pattern 30 is calculated by the light module by dividing the corresponding pixel of the alternative dataset by the value of the corresponding pixel of the reference image pattern. This coefficient pattern 30 is then used to calculate the projection image pattern, which coincides with the further image pattern 2, by multiplying the value of the reference image pattern by the corresponding value of the correction pattern. shows an automotive lighting device according to the invention, this lighting device comprising: - a light module 4 comprising a plurality of LEDs 5; - a control unit 6 to carry out the steps described in the previous figures, sending the data to the light module 4; and - a processor unit 7, the processor unit 7 being configured to generate the correction pattern and decompress the compressed data, this processor unit 7being located in the light module 4. Both the control unit 6 and the processor unit 7 comprise a buffer to store the reference image pattern, so that this reference image pattern is used during the method. Method for managing image data in an automotive lighting device (10), wherein the automotive lighting device (10) comprises a control unit (6) and a lighting module (4), the method comprising the steps of: - the control unit (6) provides the lighting module with a reference image pattern (1) comprising a plurality of pixels (11), wherein each pixel is characterized by a value related to the luminous intensity of the pixel (11); - the control unit (6) provides a further image pattern (2), comprising a plurality of pixels (21), wherein each pixel (21) is characterized by a value related to the luminous intensity of the pixel (21); - the control unit (6) calculates an alternative dataset (3) with a data number lower than the number of pixels of the further image pattern, wherein the alternative dataset (3) is related to the values of luminous intensity of the pixels (21), - the control unit (6) sends the alternative dataset (3) to the light module (4); - the light module (4) calculates a correction pattern (30), which is related to the alternative dataset (3) and the reference image pattern (1); and - the light module (4) calculates a projection pattern from the reference image pattern (1) and the correction pattern (30). Method according to claim 1, further comprising the step of buffering the reference image pattern in the light module. Method according to any of the preceding claims, wherein the light pixels (11) of the reference image pattern (1) and the light pixels (21) of the further image pattern (2) are greyscale pixels, and more particularly, the luminous intensity of each pixel (11, 21) is characterized by a number according to a scale from 0 to 255. Method according to claim 3, wherein the alternative dataset (3) is obtained by selecting strings of pixels of the further image pattern and replace each string of pixels by a linear approximation. Method according to any of claims 3 or 4, wherein the correction pattern (30) is obtained by dividing the value of a pixel of the alternative dataset (3) by the value of the corresponding pixel of the reference image pattern (1), and the projection pattern is calculated by multiplying the value of the reference image pattern (1) by the corresponding value of the correction pattern (30). Method according to any of the preceding claims, further comprising the steps of: - compressing at least a portion of the correction pattern before sending it to the light module, thus creating a compressed data; and - decompressing the compressed data by the light module. Automotive lighting device (10) comprising: - a light module (4) comprising a plurality of light sources (5); and - a control unit (6) to carry out the steps of a method according to any of the preceding claims. Automotive lighting device (10) according to claim 7, wherein the light module (4) further comprises a processor unit (7), the processor unit (7) being configured to calculate the correction pattern and decompress the compressed data. Automotive lighting device (10) according to claim 8, wherein at least the processor unit (7) comprises an image buffer to keep the first image. Automotive lighting device (10) according to any of claims 7 to 9, wherein the light sources (5) are solid-state light sources, such as LEDs.