Abstract: Encoding can involve correcting chroma components representing the chroma of an input image according to a first component representing a mapping of the luminance component of said input image used for reducing or increasing the dynamic range of said luminance component, and a reconstructed component representing an inverse mapping of said first component. At least one correction factor according to said at least one scaled chroma components can also be obtained and transmitted. Decoding can involve scaled chroma components being obtained by multiplying chroma components of an image by at least one corrected chroma correction function depending on said at least one correction factor. Components of a reconstructed image can then be derived as a function of said scaled chroma components and a corrected matrix that depends on an inverse of a theoretical color space matrix conversion and said at least one correction factor.

Abstract: Different implementations are described, particularly implementations for processing a medium dynamic range video signal are presented. In a method for processing such a video signal a medium dynamic range video signal and associated metadata are received, wherein the metadata include data representative of a peak luminance value of the medium dynamic range video signal. In addition, data representative of a peak luminance value of a presentation display are received. It is determined whether the peak luminance value of the medium dynamic range video signal is greater or lower than the peak luminance value of the presentation display. A processor is configured based on the determination, wherein the processor has a first mode to reconstruct a high dynamic range video signal based on a received standard dynamic range video signal and associated metadata, and a second mode to optimize a received high dynamic range video signal for the rendering device.

Abstract: A method comprising modifying a color correction function intended to correct initial chroma components of a current image to obtain normalized corrected chroma components for avoiding the clipping of the initial chroma components while maintaining saturation and preserving hue.

Abstract: A device applies a pre-function w=P(x) to an input signal x to obtain a first result w and applies a LUT to the first result w, wherein the LUT represents a main function ƒw(w) defined for a second grid of values Gw such that the pre-function P(x) is piecewise defined on a first grid Gx of signal values, where Gw=P(Gx). The device can further obtain the pre-function P(x), piecewise defined on the first grid Gx of the signal x and calculate the LUT with the second grid Gw=P(Gx). The piecewise pre-function P(x) can be obtained from a second pre-function Q(x) by applying Q(x) to signal values x to calculate the second grid Gw=Q(Gx) and defining the pre-function P(x) piecewise on the first grid Gx by linear interpolation of the values of the second grid Gw such that P(Gx)=Q(Gx).

Abstract: A method for decoding an image enables to preserve artistic intent at the final rendering stage by adjusting the image to luminance characteristics of the content and of the presentation display that will display the image. Values representative of luminance of both the image and the display device are obtained. Parameters of a display adaptation function are adjusted according to these values and the adjusted display adaptation function is used to decode the image. In at least one embodiment, the adjusted display adaptation function relates to a tone mapping function. Corresponding apparatus implementing the method is also described.

Abstract: The present embodiments obtain chroma components representative of the chroma components of an output image from color components representative of an input image, and if a value of a pixel in at least one of said chroma components exceeds a given value, modify the value of said pixel in at least one of said color components in such a way that the value of said pixel in said at least one of said chroma components is lower than or equals to said given value.

Abstract: A method for inverse tone mapping includes obtaining a histogram of a low dynamic range image, called LDR image and obtaining an ITMO function, allowing obtaining a pixel value of a High Dynamic Range image, called HDR image, from a pixel value of the LDR image and a gain function depending on said pixel value of the LDR image. A search process is applied using the obtained histogram to identify areas of the LDR image producing bright areas in the HDR image when the ITMO function is applied on said LDR image. Information representative of the bright areas is used to determine when modifying the gain function to ensure the HDR image respects at least one predefined light energy constraint.

Abstract: Described are methods and devices for applying a color gamut mapping process on a first image to generate a second image, where the content of the first and second images is similar but the respective color spaces of the first and second images are different. The color gamut mapping process may be controlled using a color gamut mapping mode obtained from a bitstream where the color gamut mapping mode belongs to a set comprising at least two preset modes and an explicit parameters mode. If the obtained color gamut mapping mode is the explicit parameters mode and the color gamut mapping process is not enabled for the explicit parameters mode, the color gamut mapping process may be controlled by a substitute color gamut mapping mode determined from additional data.

Abstract: Different implementations are described, particularly implementations for processing a medium dynamic range video signal are presented. In a method for processing such a video signal a medium dynamic range video signal and associated metadata are received, wherein the metadata include data representative of a peak luminance value of the medium dynamic range video signal. In addition, data representative of a peak luminance value of a presentation display are received. It is determined whether the peak luminance value of the medium dynamic range video signal is greater or lower than the peak luminance value of the presentation display. A processor is configured based on the determination, wherein the processor has a first mode to reconstruct a high dynamic range video signal based on a received standard dynamic range video signal and associated metadata, and a second mode to optimize a received high dynamic range video signal for the rendering device.

Abstract: The present embodiments relate to a method and apparatus comprising: —deriving chroma components (I) of a third image by correcting chroma components (II) of a second image according to a luma component of said second image and a reconstructed component obtained by applying a mapping function to said luma component (III) of said second image, said chroma components (II) of the second image being obtained by applying a conversion matrix to components (IV) of a first image; and —adapting coefficients of the conversion matrix which are relative to a chroma component of said third image independently of coefficients of the conversion matrix which are relative to another chroma component of said third image to ensure that there is no clipping on chroma components of the third image.

Abstract: A medium dynamic range video signal and associated metadata are received, wherein the metadata include data representative of a peak luminance value of the signal. The medium dynamic range video signal is processed in a first mode to reconstruct a high dynamic range video signal based on a received standard dynamic range video signal and associated metadata if the peak luminance value of the medium dynamic range video signal is smaller than the peak luminance value of a presentation display, and in a second mode to optimize a received high dynamic range video signal for a rendering device if the peak luminance value of the medium dynamic range video signal is greater than the peak luminance value of the presentation display.

Abstract: A method for decoding an image enables to preserve artistic intent at the final rendering stage by adjusting the image to luminance characteristics of the content and of the presentation display that will display the image. Values representative of luminance of both the image and the display device are obtained. Parameters of a display adaptation function are adjusted according to these values and the adjusted display adaptation function is used to decode the image. In at least one embodiment, the adjusted display adaptation function relates to a tone mapping function. Corresponding apparatus implementing the method is also described.

Abstract: The present principles relate to a method and device for gamut mapping from a first color gamut towards a second color gamut. The method comprises, in a plane of constant hue, obtaining a target lightness for a color on the boundary of first gamut with maximum chroma, called first cusp color; and lightness mapping of the color from the first color gamut towards the second color gamut wherein the lightness mapped color is calculated from a parabolic function applied to the color, the parabolic function mapping the first cusp color to a color having the target lightness. According to a particular characteristic, a preserved chroma is also obtained; and in case the chroma of the color is lower than or equal to the preserved chroma, the lightness mapped color is the color, and in case the chroma of the color is higher than the preserved chroma, the lightness mapped color is calculated from the parabolic function applied to the color.

Abstract: The present embodiments obtain chroma components representative of the chroma components of an output image from color components representative of an input image, and if a value of a pixel in at least one of said chroma components exceeds a given value, modify the value of said pixel in at least one of said color components in such a way that the value of said pixel in said at least one of said chroma components is lower than or equals to said given value.

Abstract: A medium dynamic range video signal and associated metadata are received, wherein the metadata include data representative of a peak luminance value of the signal. The medium dynamic range video signal is processed in a first mode to reconstruct a high dynamic range video signal based on a received standard dynamic range video signal and associated metadata if the peak luminance value of the medium dynamic range video signal is smaller than the peak luminance value of a presentation display, and in a second mode to optimize a received high dynamic range video signal for a rendering device if the peak luminance value of the medium dynamic range video signal is greater than the peak luminance value of the presentation display.

Abstract: A system and method is provided for generating a tone mapping function to reduce dynamic range of a first image to produce a second image. A luma signal and a plurality of chroma components associated with the first and second image are then determined. A gamut color correction is then performed on the second image using an adaptive function. The adaptive function is generated by comparing said luma signal and at least one chroma component of said first and second image.

Abstract: According to at least one embodiment, there is provided a device configured to compare a first set bits of formatted metadata, the formatted metadata associated with first image data both being received from an uncompressed interface, with at least one second set of bits identifying a particular formatting of said formatted metadata; and to reconstruct second image data from said first image data and parameters obtained by parsing said formatted metadata according to a particular formatting identified from the result of said comparison.

Abstract: A method for color mapping a video signal into a mapped video signal responsive to at least one color mapping function is disclosed. To this aim, at least one black point offset is determined responsive to a color encoding system of the video signal and to a color encoding system of the mapped video signal. The at least one black point offset and the at least one color mapping function are then applied on the video signal to obtain the mapped video signal.

Abstract: Encoding can involve correcting chroma components representing the chroma of an input image according to a first component representing a mapping of the luminance component of said input image used for reducing or increasing the dynamic range of said luminance component, and a reconstructed component representing an inverse mapping of said first component. At least one correction factor according to said at least one scaled chroma components can also be obtained and transmitted. Decoding can involve scaled chroma components being obtained by multiplying chroma components of an image by at least one corrected chroma correction function depending on said at least one correction factor. Components of a reconstructed image can then be derived as a function of said scaled chroma components and a corrected matrix that depends on an inverse of a theoretical color space matrix conversion and said at least one correction factor.

Abstract: Applying a color gamut mapping process on a first image to generate a second image, where the content of the first and second images is similar but the respective color spaces of the first and second images are different, can involve controlling the color gamut mapping process at least by a color gamut mapping mode obtained from a bitstream where the color gamut mapping mode belongs to a set comprising at least two preset modes and an explicit parameters mode and, if the obtained color gamut mapping mode is the explicit parameters mode and the color gamut mapping process is not enabled for the explicit parameters mode, controlling the color gamut mapping process by a substitute color gamut mapping mode determined from additional data.