FR 3102631 A1 20210430 FR 1911982 A 20191025 The invention provides a method for managing image data in an automotive lighting device (10). This method comprises the steps of providing an image pattern (1) and an alternative dataset with a data number lower than the number of pixels, wherein the alternative dataset is related to the values of luminous intensity of the pixels (11). Then, the maximum error is calculated and the alternative dataset is modified to reduce the maximum error, obtaining a modified alternative dataset. The modified alternative dataset is compressed and sent to a light module. The invention also provides an automotive lighting device (10) for performing the steps of such a method. Figure pour l’abrégé : Figure 3 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 8. 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, the method comprising the steps of - providing an image pattern comprising a plurality of pixels, wherein each pixel is characterized by a value related to the luminous intensity of the pixel; - providing an alternative dataset with a data number lower than the number of pixels, wherein the alternative dataset is related to the values of luminous intensity of the pixels, - calculating the maximum error for the alternative dataset against the values of luminous intensity of the pixels - modifying the alternative dataset to reduce the maximum error, obtaining a modified alternative dataset; - compressing the modified alternative dataset, obtaining a compressed data; and - sending the compressed data to a light module. 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 image pattern and the compression data, 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 light pattern, either for lighting or signalling, and is located inside the lighting device. The main advantage of this method is the decrease in the maximum error compared to other lossy methods which do not take into account the corrective step. A previous step of providing an alternative dataset is carried out. This alternative dataset may comprise a discretization and linearization of the luminous intensity values or any other step which may involve the loss of a small number of data in exchange of a significant decrease in the final data size. In some particular embodiments, the light pixels of the image pattern are grey scale pixels, and more particularly, the luminous intensity of each pixel is 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 modification comprises the creation of a polygonal zone where the modified alternative dataset coincides with the values of luminous intensity of the pixels. In some particular embodiments, the polygonal zone comprises pixels that provide the maximum error in the step of calculating the maximum error. The polygonal zone is a zone where the luminous intensity values of the alternative dataset are replaced by the original values of the pixels of the image pattern, so the error in this polygonal zone becomes zero. If the polygonal zone was extended to the whole region of the image pattern, there would not be any advantage in the compression rate, but combining some zones characterized by the alternative dataset with zones characterized by the original luminous intensity values, there is a possibility to customize the error threshold and the compression rate threshold. In some particular embodiments, the polygonal zone has a shape of a rectangle or a diamond. This shape is particularly advantageous, since it is easy to define and is suitable for catching the error values which are located in the centre of the image pattern, where luminous intensity is higher and therefore the errors are higher as well. In some particular embodiments, the method further comprises the step of decompressing the compressed data. This step is convenient when the original image is to be projected by the light module. In some particular embodiments, the compressed data is related only to a particular portion of the image pattern. This cropping step is useful when a big portion of the image is completely dark, so that the compression stage is focused only on the portion which include representative values. 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. In some particular embodiments, the light module further comprises a processor unit, the processor unit being configured to 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, 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 pixel matrix representing the photometry of [Fig 1]. shows an error map of a first lossy method which has been applied to the image pattern of [Fig 2]. shows an example of a polygonal zone used in a method according to the invention. shows an error map of a method according to the invention, once the step of the polygonal zone has been carried out. shows an automotive lighting device according to the invention. In these figures, the following reference numbers have been used: 1 Image pattern 11 Pixel of the image pattern 2 Polygonal zone 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 image pattern 1. Each pixel 11 of this image pattern 1 is characterized by a number according to the aforementioned scale. The compression of this image pattern 1 according to commercially available software products would offer a compression rate lower than 50%, which is unacceptable by some car manufacturers. A first lossy method is then applied to the image pattern 1. 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. shows an error map of a first lossy method which has been applied to the image pattern. This error map compares each value of luminous intensity provided by the first lossy method with the corresponding value of the original pattern of luminous intensity as in the image pattern 1. The difference is shown in this figure with a colour scale. As may be seen in the scale, the first lossy method provides a maximum error of 8 in a scale from 0 to 255, which is a good value. However, it is sometimes important to minimize the maximum error. For this purpose, the method of the invention further proposes the definition of a zone where the data for compressing is not taken from the first lossy method, but from the original image pattern. This decreases the compression rate, but also decreases the maximum error. The bigger the polygonal zone is, the higher will be both decreases. shows an example of a polygonal zone 2 which is applied in a method according to the invention. This polygonal zone 2 is a diamond shape zone which tries to include all the pixels which provide an error comprised between 4 and 8. This diamond shape is centred in the centre of the image pattern, because it is easier that the higher error pixels are located in this zone, since it is the zone with a maximum luminous intensity. In this polygonal zone 2, the values of luminous intensity of the first lossy method are directly replaced with the values of the original image pattern, so that the error in this zone becomes zero. shows an error map of the corrected method, once the step of the polygonal zone has been carried out. Inside this polygonal zone, the error is zero, and outside this polygonal zone, the error was low, so the final result is a low maximum error and a low average error. Once these steps are carried out the data is compressed, thus creating compressed data. The compression rate of this method is slightly lower than the compression rate achieved by the first lossy method without correction, but the average error and the maximum error are also lower. In any case, the compression rate is enough to fulfil some car manufacturers’ requests, so this compressed data may be sent to the light module compelling with restrictive conditions about the bandwidth. 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 compression steps described in the previous figures, generating the compressed data; and - a processor unit 7, the processor unit 7 being configured to decompress the compressed data, this processor unit being located in the light module 4. This light module would achieve a very good quality projection with an improved transmission bandwidth. Method for managing image data in an automotive lighting device (10), the method comprising the steps of: - providing an 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); - providing an alternative dataset with a data number lower than the number of pixels, wherein the alternative dataset is related to the values of luminous intensity of the pixels (11), - calculating the maximum error for the alternative dataset against the values of luminous intensity of the pixels (11) - modifying the alternative dataset to reduce the maximum error, obtaining a modified alternative dataset; - compressing the modified alternative dataset, obtaining a compressed data; and - sending the compressed data to a light module. Method according to claim 1, wherein the light pixels (11) of the image pattern (1) are greyscale pixels, and more particularly, the luminous intensity of each pixel (11) is characterized by a number according to a scale from 0 to 255. Method according to any claim, wherein the modification comprises create a polygonal zone where the modified alternative dataset coincides with the values of luminous intensity of the pixels (11). Method according to claim 3, wherein the polygonal zone comprises pixels that provide the maximum error in the step of calculating the maximum error. Method according to claim 4, wherein the polygonal zone has a shape of a rectangle or a diamond. Method according to any of the preceding claims, further comprising the step of decompressing the compressed data. Method according to any of the preceding claims, wherein the compressed data is related only to a particular portion of the image pattern (1). 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 8, wherein the light module (4) further comprises a processor unit (7), the processor unit (7) being configured to decompress the compressed data. Automotive lighting device (10) according to any of claims 8 or 9, wherein the light sources (5) are solid-state light sources, such as LEDs.