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    • 专利摘要:
    methods, apparatus, and systems for extended dynamic range (hdr) hdr to hdr tone mapping aspects of the present principles relate to methods and apparatus for mapping the tones of a wide dynamic range image. The apparatus includes a processor for performing the following steps, and the method includes the following steps: obtaining a luminance component of the wide dynamic range image; determining a curve mapping of hdr range tones to a lower hdr range; determining a compressed color image by applying hdr band tone curve mapping to a hdr range lower than the luminance component of the wide dynamic range image; wherein the hdr to hdr range tone curve mapping comprises a first part for medium and dark tone levels, and a second part for enhancements.
    公开号:BR102017005371A2
    申请号:R102017005371-7
    申请日:2017-03-16
    公开日:2018-04-03
    发明作者:Seifi Mozhdeh；Reinhard Erik；Poirier Guillaume
    申请人:Thomson Licensing；
    IPC主号:
    专利说明:

    (54) Title: METHODS, APPARATUS, AND SYSTEMS FOR EXTENDED TONE MAPPING OF WIDE DYNAMIC RANGE (HDR) HDR TO HDR (51) Int. Cl .: G06T 5/00 (52) CPC: G06T 5/00 (30 ) Unionist Priority: 16/03/2016 EP 16305291.3 (73) Holder (s): THOMSON LICENSING (72) Inventor (s): MOZHDEH SEIFI; ERIK REINHARD; GUILLAUME POIRIER (74) Attorney (s): DANIEL ADVOGADOS (ALT.DE DANIEL & CIA) (57) Summary: METHODS, APPARATUS, AND SYSTEMS FOR EXTENDED TONE MAPPING OF WIDE DYNAMIC BAND (HDR) HDR Aspects of These principles refer to methods and a device for mapping the tones of an image with a wide dynamic range. The device includes a processor to perform the following steps, in addition to the method includes the following steps: obtaining a luminance component of the image with a wide dynamic range; determining a tone mapping of hdr range tones to a lower hdr range; determination of a compressed color image when applying the hdr band tone curve mapping to a hdr band lower than the luminance component of the wide dynamic range image; the tone curve mapping from hdr range to hdr range comprises a first part for medium and dark tone levels, and a second part for highlights.
    Apply HDR2HDR tone mapping tocontent102
    Encode output 103
    1/36
    METHODS, APPARATUS, AND SYSTEMS FOR MAPPING
    EXTENDED TONE OF WIDE DYNAMIC RANGE (“HDR”) HDR TO HDR
    TECHNICAL FIELD [001] The present invention relates to image and video processing. In particular, the present invention relates to an extended wide dynamic range (HDR) to HDR tone mapping.
    BACKGROUND OF THE INVENTION [002] Luminosity by nature covers a huge range of luminance levels, from starlight to bright sunlight. However, traditional image generation technologies, both digital and analog, offer a weak experience, since they cannot parallel the wide range of luminance and contrast visible to human eyes. In response, HDR technologies are being developed to allow an extended range of color, luminance and contrast to be displayed.
    [003] HDR technologies pay attention to capture, processing and display content over a wider dynamic range than SDR technologies. Nowadays, HDR capacities of HDR screens can vary, mainly according to their maximum peak white luminance: some HDR screens can offer 500 nits, while others can reach 1000 nits or even 1500 nits.
    [004] Although HDR screens and cameras to capture HDR content are currently under development, HDR content needs to undergo a mapping of tones from HDR to LDR band in order for legacy screens to be able to reproduce the content. Similarly, HDR content prepared, for example, for a 1000 nits HDR screen needs to undergo tone mapping of a lower HDR range in order for, for example, a 500 nits HDR screen to be able to reproduce the content. Therefore, there is a need for mapping tones from a lower HDR range.
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    2/36 [005] Tone reproduction, also known as tone mapping, aims to map the original range of luminance values in an image to a lower range of luminance values that can be reproduced by a screen. Often, but not always, tone mapping is performed on a luminance channel derived from an incoming HDR color image. The output of the tone mapping can be recombined with the color information retained from the original input HDR image, so that a new color output image is produced with a dynamic range of HDR image smaller than that of the input HDR image .
    [006] The tone mapping algorithms can be classified into two broad classes. A first class can be defined as a global tone mapping. This involves applying a tone mapping function or compression functions (for example, sigmoidal functions or logarithmic functions) regardless of the luminance values of each pixel in the image or the image sequence. A second class can be defined as a local tone mapping (also known as a spatially variable tone mapping). The local tone mapping takes into account, for each pixel, the luminance value of that pixel, as well as the information of its neighboring pixels.
    [007] When the luminance value range of an input image is reduced, it is usually reduced by a very large amount, after using a tone mapping operator adapted for an HDR to LDR conversion. For example, existing tone mapping operators from HDR to LDR range compress the full luminance channel information (for example, a maximum content of 4000 nits) to fit in the very low ranges of legacy LDR screens (from, for example, 100 nits content). In contrast, an HDR tone mapping operator for
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    3/36 lower HDR range may need to reduce the range by a significantly smaller factor, for example (from a maximum of 4000 nits to 1000 nits by compressing tracks between different HDR screens). Existing HDR tone mapping operators to a lower HDR range cannot fully reproduce the HDR feel, as they compress the entire luminance range and re-scale it in a linear direction to fit the luminance range of target screen, resulting in a feeling of LDR content. Another problem is that existing HDR tone mapping operators to a lower HDR range can also reduce the contrast in the highlight pixels, the effect of which can become especially noticeable when highlights are a prevalent part of the image.
    SUMMARY OF THE PRINCIPLES OF THE INVENTION [008] Therefore, there is a need for a solution that addresses the problem of reducing the dynamic range of an HDR content in a lower hdr content corresponding to the supported range of the target screen.
    [009] One aspect of the present principles refers to methods, apparatus, systems, and a computer-readable storage medium for obtaining a luminance component of the image with a wide dynamic range; determining a tone curve mapping from hdr to hdr range; for the determination of a compressed color image when applying the hdr band tone curve mapping to a hdr band lower than the luminance component of the wide dynamic range image; the tone curve mapping from hdr range to a lower hdr range comprises a first part for medium and dark tone levels and a second part for highlights, and the first part has a slope s determined based on a measurement uniformity of a section of an image histogram corresponding to a region of image brightness.
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    4/36 [01 OJThis method for mapping the tones of a wide dynamic range input image having a peak input luminance to a lower dynamic range output image having a lower peak output luminance comprises notably the steps in:
    - obtain a luminance component of the input image;
    - determine a tone mapping of hdr range tones to a lower hdr range;
    - determining said output image by applying the hdr band to hdr band tone mapping to the luminance component of the input image;
    - the hdr range tone mapping for a lower hdr range comprises a first linear part for medium and dark tone levels and a second non-linear part for highlights, and
    - the first linear part has a slope s which is a decreasing monotonic function of a measure of uniformity of distribution of the luminance values obtained in a brightness region of a luminance histogram of the luminance values obtained from the input image such that the slope s is less than or equal to 1, but greater than or equal to the ratio of the peak output luminance and the peak input luminance / ηι “-.
    [011] Preferably, the luminance histogram's brightness region is defined as being delineated between a lower limit ζι and an upper limit í positioned in the luminance range of the input image, the lower limit being proportional to the ratio s ; peak output luminance and peak input luminance 7 ni £ Llt -.
    [012] Preferably, a medium to high limit T is defined as separating the first linear part, and the second non-linear part of the tone curve mapping is less than the peak output luminance. This medium to high T limit is
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    5/36 preferably large enough to cover more than - «1% of the pixels in that frame or image, where n is greater than or equal to 2.
    [013] Preferably, the measure of uniformity of distribution of the luminance values obtained in the brightness region is determined as a ratio between the mean deviation μ and the standard deviation υ of the number of pixels of said input image along the compartments of the brightness region of said luminance histogram.
    In a specific embodiment, the slope s is determined as follows:
    zi (-3 t 3 + 2 t a + lXl-s, D + vTG and L *! 01 <t <01 t = - where: 02 - 01, and
    - with parameters 01,02 defining the transition points of the curve that represents the slope J as a function of parameter t.
    [014] Information representing the tone curve mapping from hdr range to hdr range can be signaled. Signaling can be done using at least one element of syntax included in at least one of a Set of Image Parameters (PPS), a Set of Sequence Parameters (SPS), a Supplemental Enrichment Information message, Usability Information Video (VUI), a message from the Consumer Electronics Association (CEA), or in a header. The information from the previous video frames can be applied using a radiant integration based on a boundary between the first part and the second part.
    BRIEF DESCRIPTION OF THE DRAWINGS [015] The features and advantages of the present invention can be evident from the following detailed description, when taken in conjunction with the Figures described below:
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    6/36 [016] Figure 1 is a diagram illustrating an exemplary method of encoding an image according to the present principles.
    [017] Figure 2 is a diagram illustrating an exemplary method of encoding an image and parameters according to the present principles.
    [018] Figure 3 is a diagram illustrating an exemplary method for decoding an image or video in accordance with these principles.
    [019] Figure 4 is a diagram illustrating an exemplary device in accordance with these principles.
    [020] Figure 5 is a diagram illustrating an exemplary graph in accordance with the present principles.
    [021] Figure 6 is a diagram illustrating an exemplary graph in accordance with the present principles.
    [022] Figure 7 illustrates a histogram of luminance values of an input image to be mapped according to the diagram in Figure 3, delineating, between a lower limit ζι and an upper limit, a region of brightness of that histogram, being that the weighted values of this histogram are used to calculate the slope s of the linear part of the tone mapping curve.
    DETAILED DESCRIPTION OF THE INVENTION [023] The present principles refer to methods, apparatus and systems for mapping tones from the HDR range to a lower HDR range. An example is aimed at solving the problem of reducing the dynamic range of HDR content in relation to the lower supported range of the target screen.
    [024] An example concerns the determination of a compression factor of medium and dark tones for the pixels of medium and dark tones for an operator of mapping tones from HDR range to a lower HDR range, that is, a slope of a linear part of the luminance compression curve. An example concerns methods and an apparatus for determining the ideal slope for
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    7/36 a linear part of a tone mapping, the determination being based on the content. The similarity with an HDR input can be maintained after tone mapping, while balancing the contrast in the highlights in order to optimally reproduce the feeling of viewing HDR content, albeit on screens with a wide lower dynamic range. A director's intention may, in this case, be reproduced, since, for example, content may be graduated on a 4000 nits reference HDR screen to be optimally reproduced on a lower 1000 or 1500 hdr consumer screen. nits.
    [025] One aspect of these principles concerns the problem of decreasing the quality of the dynamic range of an HDR content when converted to a target screen with a wide lower dynamic range. One aspect of the present principles concerns the reproduction of the HDR sensation despite the compression of tones in order to fit in the target screen range.
    [026] One aspect of the present principles concerns methods, devices and systems for maintaining HDR content similar to that of an HDR source, while compressing HDR content only for very high ranges of information. This will give you the feeling of viewing HDR content, albeit on screens with a lower dynamic range. This will also allow the maintenance of a director's intention. For example, content graded on a 4000 nits reference screen will play in good quality for display on a 1000 or 1500 nits consumer screen.
    [027] The tone mapping operator which, according to the present principles, has a linear part in the middle and dark tones part of the luminance range, can be used in a variety of applications. For example, the tone mapping operator can be used in a post-production studio to assist in the process of grading HDR content and producing a secondary HDR degree with a lower peak luminance. Alternatively, from the side
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    8/36 consumer, an operator of HDR tone mapping to a range
    Lower HDR can be incorporated into an HDR consumer screen or can be integrated into a converter device.
    1. Definition of the tone mapping curve:
    [028] The luminance information for a pixel of content mapped in tones from a hdr range to a lower hdr range can be determined based on a transformation of the received content into HDR. In one example, the received HDR content can be formatted to a standard RGB color space. In one example, when the color content of a pixel / is represented in the RGB color space by values Ri, Gí, Bí, the calculation of a luminance value / per pixel / can be determined in a manner known per se:
    Equation N ° 1: U = 0.2126 XJ É + 0.7152 x ff É + 0.0722 x [029] Luminance values can be derived from any other RGB color spaces in a similar way, although with different constants that depend on the definition of each individual RGB color space. Examples of RGB color spaces are ISO RGB, ISO Extended RGB, scRGB, Adobe RGB 98, Adobe Wide Gamut RGB, Apple RGB, ROMM RGB, ProPhoto RGB, CIE (1931) RGB, as well such as the RGB spaces defined in the ITU-R Rec. BT 709, ITU-R Rec. BT 2020, ITU-R Rec. BT 470, SMPTE RP 145, and SMPTE 170M standards.
    [030] Alternatively, the luminance channel of any suitable color space, such as Yuv, Yu'v ', YCbCr, YPbPr, Y'DbDr, Y'CC, CIE Yxy, CIE Lab, CIE Luv, CIE LCh, IPT, YTQ ', EBU Y'U'V', may be used in return. In this case, the image will be transformed into such a color space, the processing of which is applied to the luminance channel, and then another color space transform can convert the image into a destination color space (which, in a example, it may be an RGB color space).
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    9/36 [031] The range of luminance values of colors in an image can be divided into three sub-bands classified in general as “dark tones”, “very light” and “midtones”. These bands intuitively correspond to the darkest parts of the image, the lightest parts of the image (usually the light sources and highlights), and the midtones, which are somewhere other than a highlight or a dark tone. The crossing point between the dark tones and the mid tones is difficult to determine analytically, and can be left as a diffuse transition region. The same applies to the crossing point between the medium and very light tones. However, approximate crossing points can be determined in a manner known per se based on the analysis of the luminance histogram of an image, which leads to three sections of the image's histogram that correspond to dark tones, midtones and very clear ones. An important aspect of mapping tones from the hdr range to a lower hdr range described below relates to the linear compression of the mid and dark tones levels (or no changes, if possible), so that the photographer's intention remains as unchanged as possible at these tone levels, and to compress the highlights in a non-linear manner. The proposed tone mapping can be applied to a color luminance channel, and the chromatic color information is corrected right afterwards in a manner known per se.
    [032] In one example, the underlying tone mapping curve from HDR range to a lower HDR range may include a “first” part of a curve for pixels with medium and dark tones and a “second” non-compressive part. highlights. The first and second parts can be separated by a medium to high crossing point corresponding, for example, to a fixed medium to high limit.
    [033] The mapping of hdr tones to a lower hdr range can be represented by a two-part tone mapping curve, with (i)
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    10/36 a first linear part for the medium and dark tones and (ii) a second non-linear part for the other highlights. The first linear part is, in this case, characterized by its dark slope and mean s. The determination of this two-part tone mapping curve can remarkably comprise the following steps:
    [034] 1. Analyze an image or video frame in order to determine if the slope s of the first linear part of the curve should have a value of 1 (no luminance compression) or if it should have a value less than 1 (current luminance compression).
    [035] 2. If the slope of the first linear part has a value less than 1, determine the value s of that slope of the first part of the tone mapping curve for the pixels in the current frame.
    [036] 3. Apply a radiant integration to the current frame to avoid flickering between frames (an option that is recommended).
    [037] 4. Adjust the second part of the tone mapping curve that will reduce the dynamic range of the highlights according to the target dynamic range. The second part of the curve is adjusted so that it connects smoothly with the first part of the tone mapping curve that was adjusted in steps 1 and 2 above.
    [038] A way for the slope s of the first linear part to be calculated according to the present invention will be detailed below in section 3.
    [039] In one example, the maximum luminance value of the input HDR content is θ the maximum luminance value that can be produced by the output HDR screen is
    In one example, the values of these variables are / mQi ¥ = 4000 nit ^ θ ip ax = 1500 Ilits.
    [040] The HDR range tone mapping operator for a lower HDR range can use a C1 tone mapping function designed for
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    11/36 full range of input luminance. As used in this document, a C1 tone mapping function is defined as a function with its first derivative being defined and continuous throughout the open range of the derivative function domain entry. Of course, the smoothness criterion is not defined in the luminance values / = ° and / = Ι 010 '.
    [041] In one example, the desired input tone mapping function is a function indicated as -UvA-d In an example, for a given frame or image of a content, this -UvA-d function linearly scales the values of input luminance 1 smaller than a medium to high limit T by means of a compression factor J (often 5 = 1 ), and compresses the luminance values greater than this limit T according to a variation of the function d „ 0W . In one example, the tone mapping operator is defined as follows:
    s / if / <τ a (l - r) + c
    Equation N ° 2:
    otherwise [042] In this example, it should be noted that the second nonlinear part of the tone mapping curve corresponds to a well-known photographic tone mapping operator “/ +1.
    [043] In one example, the three parameters Q ' c -d need to be adjusted to meet the following three conditions in order to obtain parameter C1 of the tone mapping function -Uew [044] The maximum input must be mapped for maximum output, in this case:
    r / r max Li τ-λ ι πιω LJ
    Equation N ° 3: V ') c
    In / = T , the tone mapping needs to be continuous, in this case:
    Equation N ° 4: <4.0 = sr [045] Also, at 1 = T , the gradient of the tone mapping needs to be continuous, in this case a:
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    12/36
    Equation N ° 5: di '[046] The system solution for the three unknown parameters,, results in the following:
    _ (J max - τ] X (sr - 7 ^ “°)
    Equation N ° 6: -si ™ * Equation N ° 7: c = st â
    Equation N ° 8: a ~ l max - τ [047] In another example, the methodology described above in relation to Equation N ° 2 can be implemented through a tone mapping research table with sampled input luminance values and corresponding output luminance values for real-time tone mapping.
    2. Calculation of medium to high limit for each frame of video content:
    [048] The medium to high limit T of a frame or image can be remarkably determined to be less than a standard limit t d , defined by:
    [049] Equation N ° 9: t d = if 7 ™ “-, with an example of íj = Ο.β, θ as being large enough to cover more than -« 3% of the pixels in that frame or image (with n> 0, and, in one example, n = 2 ), in order to avoid cutting very high input luminance values. Such a condition is equivalent to having less than n % of these pixels with luminance values between rM »and 7 ni £ Llt -. In one example, for the most natural scenes, the very high luminance values of a frame or image contribute to a sparse set of pixels (scene histograms with a wide dynamic range tend to show a highly curtotic distribution). For such content, the following choice of limit tends to leave less than n % of the pixels (in an example n = 2 ) to be compressed in the range of the i ™ ax [050] In the 7 ™ CJ example : = 1500 nits, The standard limit T n can be initialized to 1200. These choices of Ί and n = 2 have been experimentally
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    13/36 shown, resulting in subjectively pleasing output images.
    [051] To formulate the condition “large enough to cover more than (100 - n)% of the pixels, in a first example, the cumulative histogram of the content is used. The frequency of the input luminance / is indicated by. The value can be determined by calculating the histogram of the input luminance image with any number of compartments chosen. The cumulative histogram for the value / is indicated by U and can be found by the following:
    c 1 = yh s
    Equation N ° 10:
    [052] In one example, the final limit T of a frame or image can be defined as equal to the initial value J = t 0 when:
    rmazLi
    C * - Γ τ ·
    100 - = - <n
    Equation N ° 11:
    [053] This condition formulates the case in which there are less than n % pixels with luminance values between t d , e / m £ Llt_ . This allows changing the luminance values of more than (100- «5% of the pixels only linearly. When the condition in Equation No. 10 is not met, the breaking point (ie the knee point on the mapping curve tones) is reduced in order to increase the range of luminance values in which the input image is compressed in tone.
    [054] In an example, a value of P is indicated as follows:
    rmasiJ tf ~ C T · p = 100 - = -,
    Equation N ° 12: c , ra, ELJ [055] This parameter P indicates the percentage of pixels that have luminance values above the medium to high limit T.
    [056] Based on the determination of Equation No. 11, an example of estimating the value of the medium to high limit τ is shown below, and comprises the linear reduction of the standard limit τ π ·, as follows:
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    14/36
    Equation N ° 13:
    n <ρ <a p> a
    - being that it indicates the maximum percentage of pixels that can be compressed in only a small part of the dynamic range by mapping tones without the introduction of artifacts.
    [057] It should be noted that, according to this equation, the final limit T is equal to τ π'when P is less than n . The limit T is set to 0 when P is greater than. Whenever P is between «and, the final limit will be obtained by linear interpolation between T o and 0.
    [058] As a consequence, for any choice of, the value for the medium to high limit T for P> will be set to 0 (this determination can be made at an image level, at a block level, etc.). The value for the final limit T becomes beneficial, since more than a % of the pixels are touched when any limit greater than 0 is chosen.
    [059] In the example above, the medium to high limit T is content dependent and less than or equal to the standard limit τ π ·. The medium to high limit T prevents compression of a very large number of pixels in a small range of pixels.
    max o
    ], and results in a better visual experience.
    [060] For a set of different frames or images, that is, for video content, the estimated medium to high T limits can be different for consecutive frames, and notable variations in the intensity of consecutive video frames (“flickering”) undesirable can occur. This jitter problem can be advantageously treated by providing a correction of the medium to high TI limit for each f frame of video content. In one example, a radiant integration can be applied in order to obtain a medium to high limit 4 ™ for a frame f . The medium to high limit 4 ™ is estimated using the medium to high limit TÍ and the average to high radiant limit estimated for the
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    15/36 previous table, that is, T «.êw. An example of such an estimate is as follows:
    Equation N ° 14: = A Tt + (1 - β) τ £ βά [061] The iterative nature of Equation N ° 9 implies the fact that, for each new table below, the entire history of previous estimates is considered. The user medium to high limit parameter [hi] controls the smoothness of Uw between frames.
    [062] In one example, the luminance values are derived from the RGB color values according to Equation 1. In order to reconstruct a color mapped map in tones, a simple approach at the pixel level is used. The pixel-level approach scales the RGB R ', G', B 'values of the colors of the original HDR image according to the scale change in the luminance channel defined by the tone mapping function defined in Equation 2, as follows :
    Equation N ° 15a: Roilt Equation N ° 15b: Gmit Equation N ° 15c:
    [063] The reconstruction of a color image can be parameterized by parameter that controls the amount of saturation as follows:
    Equation N ° 16a:
    Equation N ° 16b:
    Equation N ° 16c:
    [064] In one example, the tone mapping operator can be incorporated into a consumer electronic device, such as a converter device, a television, a monitor, a laptop, a phone, a tablet computer, a smartphone screen , etc. In this case, the tone mapping algorithm can be supplied with metadata in order to determine the
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    16/36 visual appearance of your output.
    3. Calculation of the slope s of the linear part of the tone mapping curve:
    [065] Once again, an example of the present principles refers to a tone mapping from hdr range to a lower hdr range that changes a slope 5 of the first part of the tone mapping curve based on the content of the input image or of the video frame.
    [066] In one example, the slope s of the first part can be determined based on a form of a luminance histogram of the input image or a video frame, notably based on the shape of a long tail in a region of brightness of this histogram.
    [067] An aspect of the present principles is then directed to the analysis of a luminance histogram in order to determine the presence of a uniform distribution of the luminance values in a brightness region of that histogram. The slope J can, in this case, be determined based on a measure of uniformity of distribution of the luminance values in that region of brightness.
    [068] In one example, a hi luminance histogram (UB, 0 of the input image / is determined for a given number of histogram compartments b distributed over the entire dynamic range of the input image. In one example, the number of histogram compartments b can have a value of 40. The * parameter indicates a vector of the centers of the histogram compartments A histogram is usually represented as an arrangement that has a value in each arrangement element. that the array index corresponds to a small range of luminance values, and the value stored in that array element (the 'compartment value') represents the number of pixels that fall within that range of luminance values. compartment can correspond to the number of pixels of a histogram that falls
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    17/36 in the respective compartment. The histogram is previously calculated and indicated in the preceding text by, a, O.
    [069] In one example, the brightness region of the image histogram is defined by the CACl · limits corresponding to the lowest luminance value and the highest luminance value of that brightness region, respectively. These limits outline the range of tones that will be analyzed for the measurement of distribution uniformity and, thus, also outline the brightness region of the histogram to be considered in order to calculate the slope s.
    In one example, the lower limit ζι is determined as follows:
    Equation N ° 17: Ω = J ni “-,
    - giving, when combined with Equation N ° 9, the index;
    J □>
    , β η-—
    Equation N ° 18: Ci = i ™ - where B is the number of compartments in the histogram, with the maximum luminance value of the input HDR content θ provided, for example, as metadata with the video content, the value being maximum output luminance output A 1 ** - is typically derived from the peak screen luminance of the target screen. Equation N ° 18 means that the lower limit Ci is proportional to the ratio N of the peak output luminance A 1 ** - and the peak input luminance.
    In one example, the upper limit C ^ is determined as follows:
    Equation N ° 19: Α = β £ [070] The parameters h (already defined above) and £ must both be in the range J-— between 0 and 1. In addition, £ must be greater than. Based on the observations of graduated content, a good value of h will be 0.8. A default value of the £ parameter can be set to 0.75.
    [071] In addition, it will be possible to use metadata in order to adjust the parameters η and £ , instead of using default values. This can be useful in cases where the cinematographer wants to provide guidance as to how content
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    18/36 can be mapped in tones in such a way as to preserve the director's intention. In that case, these parameters will be specified during (post-) production and will be attached to the content as metadata. A device that receives this content, in this case, will be able to adjust the tone reproduction parameters on that basis.
    [072] It should be noted that the medium to high limit that outlines the first and second parts of the tone mapping curve, as described above, is, in general, different from the lower limit and the upper limit that outlines the brightness region.
    [073] In one example, the luminance histogram compartments of the input image are analyzed between the ζι, ζκ limits, that is, in the so-called brightness region. See Figure 7.
    [074] In an alternative example, a weighting function can be remarkably determined based on these limits. The weighting function can determine a weighting for each compartment B of the luminance histogram, such that, when applied to each compartment B , the effect of histogram values that have a value less than the lower limit ζι or greater than the limit top is removed. The dotted line in Figure 7 illustrates such a weighted distribution of luminance values in the region of brightness.
    [075] For the manufacturer of Systems on a Chip (SOC), it can be expensive to implement conditional phrases, depending on what it can be expensive to use both limits (iSu on SOC devices. In one example, the entire histogram can be weighted with weights equal to 1 between the two limits (ι / u, eOem at any point. Obtaining the weights may provide a more robust solution for the variation of content than with the use of the two rigid limits (i / u.
    [076] In one example the weighting function is determined as the convolution of a square window function (í - íi B ) (with defined values
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    19/36 in 1 for f between ζι and Ά and 0 at any point) with a discrete symmetric Hamming window Q tf A) from the support of Equation N ° 15.
    Equation N ° 20: L 'Sxb.
    [077] In an example, Figure 5 illustrates certain weights for a histogram with b = 4o [078] The weights «GAiAií- b ) can be determined using the following equation:
    Equation N ° 21: * GAi A- B ) = φ, ζι-u- B ) * 0. tf A]
    - where * indicates the convolution operator, and the discrete Hamming window (Q tfA) is determined as follows:
    q L) = 0.S + - 0.46 x cos
    Equation N ° 22:
    [079] In one example, a histogram is multiplied by the weightings M GAi Au-b) resulting in the following weighting with respect to the histogram compartments:
    Equation N ° 23: kl 'Ú -B, O = hi <Z, b GAi Ab) [080] Figure 5 illustrates certain weights ^ GAiAu-b) to be applied to the image histogram for b = 40, ζ, = τ α ,, ζ η = 0.75 / ^ -, 1 = 6.
    [081] The histogram compartments between the fiAu limits or the weighted histogram of Equation No. 18 form an adequate basis for measuring the uniformity of the distribution of luminance values in order to calculate the slope s. Although any method for determining the uniformity of the corresponding set of luminance values can be applied, in one example, uniformity can be determined based on the mean deviation M and the standard deviation υ of the weighted histogram (or the histogram between the limits iAh ), which can be determined as follows:
    Equation N ° 24: P = avg t [ln '(/, B, i)}
    Equation No. 25: = std ; [IA (/, b, i)}
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    20/36 [082] In one example, the measure of uniformity is then given by the ratio of the mean deviation and the standard deviation of the weighted histogram (or of the unweighted histogram between the limits), as follows.
    μ
    Equation N ° 26: measure of uniformity = u.
    [083] The measure of uniformity can correlate with an adequate determination of the slope s of the first linear part of the tone mapping operator. In more specific terms, this slope s becomes a decreasing monotonic function of this measure of uniformity. In an example illustrated μ in Figure 6, the relationship between slope J and the measure of uniformity u is determined in a non-linear manner, for example, as follows.
    [084] In one example, slope 5 can be determined as a μ function of u, as follows:
    • 1 (-3 ^ + 2 ^ + lXl-sJ + s, and L <t <θι
    Equation N ° 27: 5i [085] In one example, parameter N can be determined as follows:
    JTJIQÍ J
    Equation N ° 28: _ [086] Parameter N (<1 according to the definitions above e) ensures that the slope J of the linear part of the tone mapping curve is not less than the peak output luminance ratio _ e of the input luminance peak F 1 1 . this may result in the prevention of an undesirable large reduction in contrast in dark tones.
    μ [087] The parameter t is based on the uniformity measure u, as follows:
    u t = -——
    Equation N ° 29: - Si [088] This equation used to apply a re-scale to the measure of μ uniformity u using the constants ei-ez. In one embodiment, these constants can be defined as 61 = 0.5 ^ = 0.85. In Equation 27, these same
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    21/36 constants lend themselves as the transition points that outline the non-linear part of the constant parts.
    [089] In one example, Figure 6 illustrates the given slope 5 as £ a function of υ.
    Block diagram of the tone mapping method described above:
    [090] The examples described above can be implemented within the figures described below.
    [091] Figure 1 is a diagram illustrating an exemplary method 100 for encoding video or image content in accordance with the present principles.
    [092] Method 100 may include receiving and encoding an image. The image can be encoded in a bit stream using any encoding technique (for example, HEVC, AVC). Method 100 can be performed on any type of workflow, such as distribution workflows based on the DVB or ATSC standard, production or authoring workflows, on digital video camcorder devices.
    [093] In one example, method 100 includes the receiver of an image in block 101. The image can be part of a sequence of video images or screens, for example, for an HDR video. Block 101 can receive information regarding image properties, including RGB linear light information. The image can be captured using trichromatic cameras in RGB color values composed of three components (Red, Green and Blue) (Red, Green and Blue). The RGB color values depend on the trichromatic characteristics (the primary colors) of the sensor. The image can include image information, such as primary sensor colors, maximum and minimum peak luminance of the captured scene. Block 101 can then pass control to block 102, including the provision of any information related to the image received.
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    22/36 [094] Block 102 can apply a hdr range tone mapping to a lower hdr range than the content received from block 101. The hdr range tone mapping to a lower hdr range can be determined according to the gifts Principles. Mapping hdr tones to a lower hdr range converts the dynamic range of the content to fit the dynamic range of the screen.
    [095] The mapping HDR tonal range to a lower range HDR can be determined based on the principles described above also with respect to Equations Nos 1 to 8 and 15 to 16. In particular, the mapping HDR tonal range for a lower hdr range it can be used when the amount of range reduction is limited. The mapping HDR tonal range to a lower range HDR can be determined in accordance with the principles described above, including the principles described with reference to Equations Nos 1 to 24.
    [096] Block 103 can encode the output of block 102. Block 103 can encode the output according to any existing encoding / decoding standard. For example, block 103 can encode according to the High Efficiency Video Coding (HEVC) standard organized by the International Telecommunication (ITU) organization or the Moving Picture Experts Group (MPEG). Alternatively, block 103 can encode according to the H.264 or MPEG-4 Part 10 standard, the Advanced Video Encoding (MPEG-4 AVC) established by the International Organization for the International Standardization Electrotechnical Commission (ISO / IEC ) of the Moving Picture Experts Group-4 (MPEG-4). Alternatively, block 103 may encode with any other known coding technique.
    [097] Figure 2 is a diagram illustrating an exemplary method 200 for encoding an image and parameters. Method 200 includes a block 201 for the
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    23/36 receiving parameters for a content dependent limit. The received parameters can be as follows:
    - the peak luminance of the output content or the target screen can be supplied by the television / monitor itself. If a converter device is used, this value can be signaled by a connected video device, for example, via an HDMI message.
    - the peak luminance of the input content can be encoded as metadata together with the content. It may be provided as a single value per frame, per shot, or per program (television episode, film, advertisement, etc.). In an alternative example, the value of can be interpreted as the peak luminance of a video device used to generate the input content (for example, in a post-production house), or as the peak luminance of a live camera used in a broadcast scenario in order to create the input content.
    - the parameter η, defined as the ratio of the standard limit T ne of the maximum luminance value produced by the output HDR image (See Equation N ° 9), can be sent together with the content as metadata. In an alternative example, the limit T , which determines the crossing between the linear and non-linear parts of the tone mapping curve, can be sent in return.
    - the parameter «, which determines the percentage of pixels to be subjected to non-linear compression, can additionally be supplied as metadata.
    - the parameter can also be supplied as metadata.
    - the parameter β that is used in the radiant integration of the limit of the limit for video content can also be included in the metadata.
    - parameter b which is the number of histogram compartments can also be supplied as metadata.
    - the parameter ; indicates a vector of the centers of the compartments of the
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    24/36 histogram that can also be supplied as metadata.
    - the parameter £ that controls the upper limit in the midtone region of the histogram can also be supplied as metadata.
    [098] The parameters received in block 201 can be used so that the intention of a content producer (director of photography, colorist, studio) is reproduced on a wide variety of screens.
    [099] Block 202 can determine the tone mapping curve parameters. The tone mapping curve parameters may be determined based on Equation 6 to C 8 and 27. The block 208 may encode the parameters determined by block 202.
    [0100] Block 203 can receive an image. In one example, block 203 can receive an image according to the principles outlined with respect to block 101 of Figure 1.
    [0101JO block 204 can obtain luminance channel information from the received image. In one example, block 204 may apply a preliminary color transform in order to obtain luminance channel information from the received image. In one example, block 204 can apply a preliminary color transform in order to obtain luminance channel information. In one example, block 204 can determine luminance channel information according to the principles described in relation to Equation No. 1. In another example, block 204 can be optional and luminance information can be directly received from the block. 203.
    [0102] Block 205 can apply hdr range tone mapping to a lower hdr range. In one example, block 205 can apply hdr range tone mapping to a lower hdr range according to the principles described in relation to block 102 of Figure 1. In one example, block 205 can apply tone tone mapping. hdr range to hdr range to determine an image
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    25/36 processed Io output.
    [0103] Block 206 can make a color correction at the output of block 205. Block 206 can send a color corrected output image. Block 207 can code the output of block 206.
    [0104] Block 209 can send to the bit stream the parameters encoded by block 208 and the output image encoded by block 207.
    [0105] Figure 3 is a diagram illustrating an exemplary method 300 for decoding an image or video in accordance with the present principles.
    [0106] Block 301 can receive a bit stream corresponding to a video or image sequence. The received bit stream is encoded (for example, using AVC, HEVC, etc.). Block 301 can then pass control to block 02.
    [0107] Block 302 can analyze and decode the bit stream received from block 301. In one example, block 302 can analyze and decode the bit stream using HEVC-based decoding. Block 302 can then pass control to block 303.
    [0108] Block 303 can obtain luminance channel information. In one example, block 303 may be optional. In one example, block 303 may obtain the luminance channel information according to the principles described with reference to Equation No. 1. The block 303 may then pass control to the blocks 304 and 305.
    [0109] Block 304 can determine the parameters for mapping tones from hdr range to a lower hdr range according to the present principles. The parameters can be any parameters described in this document in accordance with these principles. In one example, parameters are determined on a basis outside the syntax contained in the bit stream (for example, a SEI message). The parameters can be the parameters described with
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    26/36 with respect to block 202. These parameters can be transmitted via the bit stream, or they can also be determined in the decoder. These parameters are estimated in an example from the histogram of the luminance information.
    [0110] Block 305 can process a video signal. In one example, block 305 can process a Y'CbCr decoded video signal. In one example, block 305 can convert a Y'CbCr video signal to a R'G'B 'video signal. In another example, block 305 can process a R'G'B 'video signal.
    [0111] Block 306 can apply hdr range tone mapping to a lower hdr range than the video signal. Block 306 can be done frame by frame using the corresponding estimated parameters. In one example, block 307 can apply tone mapping from hdr range to a lower hdr range according to the principles described in relation to blocks 102 and 205. In one example, block 307 can create or receive a Lookup Table (LUT) with tabulated values and apply the LUT table to the content to be mapped / unmapped.
    Architecture of a device configured to implement the tone mapping method:
    [0112] Figure 4 depicts an exemplary architecture of a device 400 that can be configured to implement the methods described with reference to Figures 1 to 3 and Equation Nos 1 to 24. In an example, Figure 4 represents a apparatus that can be configured to implement the coding method according to the present principles, including the principles described in relation to Figures 1 to 3. In an example, Figure 4 represents a device that can be configured in order to implement the decoding method according to the present principles, including the principles described in relation to Figure 3.
    [0113] The device 400 comprises the following elements that are linked together by means of a data bus and address 401:
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    27/36
    - a 402 microprocessor (or CPU), which is, for example, a DSP (or a Digital Signal Processor);
    - a ROM (or Read-Only Memory) 403;
    - a RAM memory (or Random Access Memory) 404;
    - an I / O 405 interface for receiving and transmitting data from an application; and
    - a 406 battery (or other suitable power source).
    [0114] According to a variant, the 406 battery is external to the device. In each of the aforementioned memories, the word register used in the specification can correspond to an area of small capacity (a few bits) or to a very large area (for example, an entire program or a large amount of data received or decoded) . ROM 403 comprises at least one program and its parameters. The algorithm of the methods according to the present invention is stored in ROM 403 memory. When activated, CPU 402 loads the program from RAM memory and executes the corresponding instructions.
    [0115] RAM 404 comprises, in a register, the program executed by CPU 402 and sent after the activation of device 400, the input data in a register, the intermediate data in the different method states in a register, in addition to other variables used to execute the method in a register.
    [0116] The implementations described in this document can be implemented, for example, in a method or in a process, in an apparatus, in a software program, in a data flow, or in a signal. Even if only described in the context of a single form of implementation (for example, described only as a method or a device), the implementation of the described features can also be done in other ways (for example,
    Petition 870170017487, of 03/16/2017, p. 47/56
    28/36 through a program). A device can be implemented, for example, in appropriate hardware, software, or firmware. The methods can be implemented, for example, on an apparatus, such as, for example, a processor, which refers to processing devices in general, including, for example, a computer, a microprocessor, an integrated circuit, or a device programmable logic. Processors also include communication devices, such as, for example, computers, cell phones, portable / personal digital assistants (PDA), as well as other devices that facilitate the communication of information between end users.
    [0117] According to a specific example of encoding or encoder, the image or scene I is obtained from a source. For example, the source belongs to a set comprising:
    - a local memory (403 or 404), for example, a video memory or a RAM memory (or Random Access Memory), a flash memory, a ROM memory (or Read Only Memory), a hard disk;
    - a storage interface (405), for example, an interface with mass storage, a RAM memory, a flash memory, a ROM memory, an optical disk or a magnetic medium;
    - a communication interface (405), for example, a physical interface (for example, a bus interface, a remote network interface, a LAN interface) or a wireless interface (such as an IEEE 802.11 interface or a Bluetooth® interface); and
    - an image capture circuit (for example, a sensor, such as, for example, a CCD (or Coupled Load Device) or a CMOS (or Complementary Metal Oxide Semiconductor).
    [0118] According to different decoding or decoding modalities, the decoded image I is sent to a destination; in terms
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    29/36, the destination belongs to a group comprising:
    - a local memory (403 or 404), for example, a video memory or a RAM memory, a flash memory, a hard disk;
    - a storage interface (405), for example, an interface with mass storage, a RAM memory, a flash memory, a ROM memory, an optical disk or a magnetic medium;
    - a communication interface (405), for example, a physical interface (for example, a bus interface (for example, USB (or Universal Serial Bus)), a remote network interface, a LAN interface, an interface HDMI (High Definition Multimedia Interface)) or a wireless interface (such as an IEEE 802.11 interface, Wi-Fi ® or a Bluetooth ® interface); and
    - a screen.
    [0119] According to different coding or encoder examples, the BF and / or F bit stream is sent to a destination. As an example, one of the F or BF bit streams or both F and BF bit streams are stored in a local or remote memory, for example, a video memory (404) or a RAM memory (404), a hard disk (403). In a variant, one or both of the bit streams are sent to a storage interface (405), for example, an interface with mass storage, flash memory, ROM memory, optical disk or magnetic media and / or transmitted by a communication interface (405), for example, an interface to a point-to-point link, a communication bus, a point link to multiple points or a broadcast network.
    [0120] According to different decoding or decoder examples, the BF and / or F bit stream is obtained from a source. In an exemplary way, the bit stream is read from a local memory, for example, a video memory (404), a RAM memory (404), a ROM memory (403), a
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    30/36 flash memory (403) or a hard disk (403). In a variant, the bit stream is received from a storage interface (405), for example, an interface with mass storage, RAM, ROM, flash memory, optical disc or media magnetic and / or received from a communication interface (405), for example, an interface for a point-to-point link, a bus, a point for a multi-point link or a broadcast network.
    [0121] According to different examples, the device 400 which is configured to implement an encoding method according to the present principles, belongs to a set comprising:
    - a mobile device;
    - a communication device;
    - a gaming device;
    - a tablet (or tablet computer);
    - a portable computer;
    - a still image camera;
    - a video camera;
    - an encoding chip;
    - a still image server; and
    - a video server (for example, a broadcast server, a video on demand server or a web server).
    [0122] According to different examples, the device 400 which is configured to implement a decoding method in accordance with the present principles, belongs to a set comprising:
    - a mobile device;
    - a communication device;
    - a gaming device;
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    31/36
    - a converter device;
    - a TV set;
    - a tablet (or tablet computer);
    - a portable computer;
    - a screen; or
    - a decoder chip.
    [0123] The implementations of the various processes and features described in this document can be incorporated into a variety of different equipment or applications. Examples of such equipment include an encoder, a decoder, a post-processor that processes the output of a decoder, a pre-processor that provides input to an encoder, a video encoder, a video decoder, a video codec, a web server, converter device, laptop, personal computer, cell phone, PDA, or other communication devices. Of course, this equipment can be mobile or even installed in a mobile vehicle.
    [0124] In addition, methods can be implemented through instructions that are performed by a processor, and such instructions (and / or data values produced by an implementation) can be stored in a processor-readable medium, such as, for example, an integrated circuit, a software carrier or other storage device, such as, for example, a hard disk, a compact diskette (“CD”), an optical disc (such as, for example, a DVD, many sometimes referred to as a digital versatile disk or digital video disk), a random access memory (“RAM”), or a read-only memory (“ROM”). Instructions can form an application program tangibly embedded in a processor-readable medium. Instructions can be, for example, on hardware, firmware, software, or a
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    32/36 combination thereof. The instructions can be found, for example, in an operating system, in a separate application, or in a combination of these two. A processor can therefore be characterized, for example, either as a device configured to execute a process or a device that includes a readable medium per processor (such as a storage device) having instructions for executing a process. In addition, a processor-readable medium can store, in addition to or instead of instructions, data values produced through an implementation.
    [0125] As will become apparent to a person skilled in the art, these implementations can produce a variety of formatted signals in order to carry information that can, for example, be stored or transmitted. The information may include, for example, instructions for carrying out a method, or data produced by one of the described implementations. For example, a signal may be formatted to load as data the rules for writing or reading a syntax from a described example, or to load as data the current recorded syntax values as described. This signal can be formatted, for example, as an electromagnetic wave (for example, using a radio frequency portion of a spectrum) or as a baseband signal. Formatting can include, for example, encoding a data stream and modulating a carrier with the encoded data stream. The information that the signal carries can be, for example, analog or digital information. The signal can be transmitted via a variety of different wired or wireless links, such as known. The signal can be stored in a readable medium per processor.
    [0126] Several implementations have been described. However, it must be understood that several modifications can be made. For example, elements from different implementations can be combined, supplemented, modified, or
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    33/36 withdrawn in order to produce other implementations. In addition, a person with simple knowledge in the art may understand that other structures and processes may be replaced by the process structures described in this document and that their resulting implementations may perform at least substantially the same functions, at least substantially in the same ways, in the achieve at least substantially the same results as the described implementations. Therefore, these and other implementations are contemplated by the present application.
    [0127] Numerous specific details have been described in this document in order to provide a complete understanding of the present invention. It should be understood by those skilled in the art, however, that the examples above can be practiced without these specific details. In other instances, well-known operations, components and circuits have not been described in detail so as not to obscure the present invention. It can be appreciated that the specific structural and functional details described in the present document can be representative and do not necessarily limit the scope of the present invention.
    [0128] Various examples of the present invention can be implemented using hardware elements, software elements, or a combination of both. Some examples can be implemented, for example, using a computer-readable medium or article that can store an instruction or set of instructions that, when executed by a machine, may cause the machine to perform a method and / or operations according to the examples. Such a machine may include, for example, any processing platform, computing platform, computing device, processing device, computing system, processing system, computer, processor, suitable or the like, or may be
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    34/36 implemented using any suitable combination of hardware and / or software. The computer-readable medium or article may include, for example, any suitable type of memory unit, memory device, memory article, memory medium, storage device, storage article, storage medium and / or storage unit . The instructions can include any suitable type of code, such as, a source code, a compiled code, an interpreted code, an executable code, a static code, a dynamic code, an encrypted code, or the like, can be implemented using any high-level, low-level, object-oriented, visual, compiled and / or interpreted programming language.
    [0129] The implementations described in this document can be implemented, for example, in a method or in a process, in an apparatus, in a software program, in a data flow, or in a signal. Even if only presented in the context of a single form of implementation (for example, presented only as a method), the implementation of the characteristics presented can also be done in other ways (for example, as an appliance or program). An apparatus and its constituents included in this document, for example, a processor, an encoder or a decoder, can be implemented, for example, in appropriate hardware, software, or firmware. The methods can be implemented, for example, in a device, such as, for example, in a processor, which refers to processing devices in general, including, for example, a computer, a microprocessor, an integrated circuit, or a programmable logic device. Processors also include communication devices, such as, for example, computers, cell phones, portable / personal digital assistants (PDAs), as well as other devices that facilitate the communication of information between end users.
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    35/36 [0130] In addition, this application or its claims may refer to the “determination” of various information. Determining information can include one or more of, for example, estimating information, calculating information, predicting information, or retrieving information from memory.
    [0131] In addition, this application or its claims may refer to “access” to various information. Access to information may include one or more, for example, receiving information, retrieving information (for example, from memory), storing information, processing information, transmitting information, moving information, copying information, deleting information, calculating information, determining information, predicting information, or estimating information.
    [0132] In addition, this request or its claims may refer to the "receipt" of various information. Receipt should be understood, in broad terms, as "access". Receipt of information may include one or more of, for example, access to information, or retrieval of information (for example, from memory). In addition, “receiving” typically refers, in one way or another, during operations, for example, as storing information, processing information, transmitting information, moving information, copying information , deleting information, calculating information, determining information, predicting information, or estimating information.
    [0133] According to different modalities, the parameterized transfer function is signaled in the encoded or decoded image according to the present invention, or in a flow that includes the image. In some modalities,
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    36/36 information representative of the parameterized transfer function is signaled in the image or in the flow including the image. This information is used by a decoding or decoding method in order to identify the parameterized transfer function that is applied in accordance with the present invention. In one embodiment, this information includes a known identifier for encoding and decoding. According to other modalities, this information includes the parameters used as a basis for the parameterized transfer functions. According to a variant of the present invention, this information comprises an indicator of the parameters in the image or in a bit stream including the image, based on a set of defined values. According to a variant of the present invention, this information comprises an indication based on whether the parameters are explicitly flagged or whether the parameters are implicitly flagged based on a set of defined values. According to different variants of the present invention, this information is included in at least one element of syntax included in at least one of a Set of Image Parameters (PPS), a Set of Sequence Parameters (SPS), an Information message Supplemental Enrichment, Video Usability Information (VUI), a message from the Consumer Association of Electronic Products (CEA), or in a header.
    [0134] The present invention also relates to an encoding and decoding apparatus adapted for carrying out, respectively, the above encoding and decoding methods.
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    权利要求:
    Claims (13)
    [1]
    1. Method for mapping the tones of a wide dynamic range input image having a peak input luminance f maxLJ to a lower dynamic range output image having a lower peak output luminance, the method being CHARACTERIZED by understanding the steps of:
    - obtain a luminance component of the input image;
    - determine a tone mapping of hdr range tones to a lower hdr range;
    - determining said output image by applying the hdr band to hdr band tone mapping to the luminance component of the input image;
    - the hdr range tone mapping for a lower hdr range comprises a first linear part for medium and dark tone levels and a second non-linear part for highlights, and
    - the first linear part having a slope s that becomes a decreasing monotonic function of a measure of uniformity of distribution of the luminance values obtained in a brightness region of a luminance histogram of the luminance values obtained from the input image such that said slope s is less than or equal to 1, but greater than or equal to the ratio of the peak output luminance and the peak input luminance.
    [2]
    2. Method according to claim 1, wherein the brightness region of the luminance histogram is defined as being delineated between a lower limit ζι and an upper limit ζυ. positioned in the luminance range of the input image, the method being CHARACTERIZED by the fact that the lower limit ζι is proportional to the ratio of the peak output luminance and the peak input luminance f maxLJ .
    [3]
    3. Method, according to claim 1 or 2, CHARACTERIZED by
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    2/3 the fact that a medium to high limit T defined as separating the first linear part and the second non-linear part of the tone curve mapping is less than the peak output luminance.
    [4]
    4. Method, according to claim 3, CHARACTERIZED by the fact that the medium to high limit T is large enough to cover more than <i °° -% of the pixels in this frame or image, where n is greater than or equal to 2.
    [5]
    5. Method according to any one of claims 1 to 4, CHARACTERIZED by the fact that the measure of uniformity of distribution of the luminance values obtained in the brightness region is determined as a ratio between the mean deviation Meo and standard deviation v of the number of pixels of said input image along the compartments of the brightness region of said luminance histogram.
    [6]
    6. Method according to any one of claims 1 to 5, CHARACTERIZED by the fact that the relationship between the slope s and the uniformity measure is non-linear.
    [7]
    7. Method, according to claim 6 when dependent on claim 5, CHARACTERIZED by the fact that the slope s is determined as follows: ri (-3 ^ + 2 ^ + lXl-s,] + sj <t <Qi
    - where: Qi, and
    - the parameters ei.ez define the transition points of the curve that represents the slope J as a function of the parameter t.
    [8]
    8. Method, according to any one of claims 1 to 7, CHARACTERIZED by the fact that it also comprises the step of signaling the representative information of the tone curve mapping from hdr range to a lower hdr range.
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    [9]
    9. Method, according to claim 8, CHARACTERIZED by the fact that the signaling step is performed using at least one element of syntax included in at least one of a Set of Image Parameters (PPS), a Set of Parameters of Image Sequence (SPS), a Supplemental Enrichment Information message, Video Usability Information (VUI), A Consumer Electronics Association (CEA) message, or in a header.
    [10]
    10. Device for mapping the tones of a wide dynamic range input image having a peak input luminance f maxLJ in an output image of a wide dynamic range, but lower having a lower peak output luminance, the device being CHARACTERIZED by the fact that it comprises at least one processor configured to implement the method according to any one of claims 1 to 9.
    [11]
    11. Electronic device, CHARACTERIZED by understanding the device according to claim 10.
    [12]
    12. Electronic device, according to claim 11, CHARACTERIZED by the fact that it is selected from the group consisting of a mobile device, a communication device, a gaming device, a tablet computer, a portable computer, a camera, a encoder chip, and a server.
    [13]
    13. Computer program product comprising program code instructions, the computer program product being CHARACTERIZED by the fact that it performs the steps of the method according to any one of claims 1 to 9, when that program is executed on a computer.
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    100
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    同族专利:
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    EP3220349A1|2017-09-20|
    KR102291954B1|2021-08-23|
    EP3220350B1|2018-11-28|
    CN107203974B|2021-11-23|
    US20170272690A1|2017-09-21|
    JP2017168101A|2017-09-21|
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    KR20170107929A|2017-09-26|
    CN107203974A|2017-09-26|
    EP3220350A1|2017-09-20|
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    法律状态:
    2018-04-03| B03A| Publication of a patent application or of a certificate of addition of invention [chapter 3.1 patent gazette]|
    2019-07-16| B25G| Requested change of headquarter approved|Owner name: THOMSON LICENSING (FR) |
    2019-07-30| B25A| Requested transfer of rights approved|Owner name: INTERDIGITAL VC HOLDINGS, INC. (US) |
    2021-08-10| B25A| Requested transfer of rights approved|Owner name: INTERDIGITAL MADISON PATENT HOLDINGS, SAS (FR) |
    优先权:
    申请号 | 申请日 | 专利标题
    EP16305291.3A|EP3220349A1|2016-03-16|2016-03-16|Methods, apparatus, and systems for extended high dynamic rangehdr to hdr tone mapping|
    EP16305291.3|2016-03-16|
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