WO2015022274A1 - Image processing method and device, image restitution method and device, and corresponding computer program and system - Google Patents

Image processing method and device, image restitution method and device, and corresponding computer program and system Download PDF

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Publication number
WO2015022274A1
WO2015022274A1 PCT/EP2014/067102 EP2014067102W WO2015022274A1 WO 2015022274 A1 WO2015022274 A1 WO 2015022274A1 EP 2014067102 W EP2014067102 W EP 2014067102W WO 2015022274 A1 WO2015022274 A1 WO 2015022274A1
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WIPO (PCT)
Prior art keywords
image
gamut
belong
images
mask
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PCT/EP2014/067102
Other languages
French (fr)
Inventor
Corinne Poree
Emmanuel Jolly
Patrick Morvan
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Thomson Licensing
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Publication of WO2015022274A1 publication Critical patent/WO2015022274A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/46—Colour picture communication systems
    • H04N1/56—Processing of colour picture signals
    • H04N1/60—Colour correction or control
    • H04N1/6027—Correction or control of colour gradation or colour contrast
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T5/00—Image enhancement or restoration
    • G06T5/50—Image enhancement or restoration by the use of more than one image, e.g. averaging, subtraction
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/90—Determination of colour characteristics
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/46—Colour picture communication systems
    • H04N1/56—Processing of colour picture signals
    • H04N1/60—Colour correction or control
    • H04N1/603—Colour correction or control controlled by characteristics of the picture signal generator or the picture reproducer
    • H04N1/6052—Matching two or more picture signal generators or two or more picture reproducers
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/10—Image acquisition modality
    • G06T2207/10024—Color image
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/20—Special algorithmic details
    • G06T2207/20172—Image enhancement details
    • G06T2207/20208—High dynamic range [HDR] image processing

Definitions

  • the field of the invention is that of image processing and restitution, and notably processing and restitution of a video stream comprising a succession of images.
  • the invention relates to the colourimetry of the restituted images and proposes a technique making it possible to extend the colourimetry simply in certain regions of an image, that is to say to restitute the image using a wider range of colours in certain regions of the image.
  • the invention notably finds applications in the restitution of images on terminals which can display a wide range of colours, and more specifically in the restitution of HD (high dynamic range) images, or the restitution of WCG (wide colour gamut) images.
  • the range of colours of the content to be restituted is often limited during the creation or the transmission of the content to be restituted.
  • the images composing the video have colours belonging to a standard range of colours, called a standard gamut.
  • the colours of the content to be restituted are modified, in order to "extend" the colours of the content to be restituted to the extended gamut.
  • the primary colours blue, red and green of the standard gamut of the content to be restituted and the primary colours blue, red and green of the extended gamut of the restitution terminal are matched, and the colour space defined between these two gamuts is extended.
  • a disadvantage of this technique is that it performs a global extension of the whole of the image to be restituted, which notably leads to an oversaturation of flesh, pastel or neutral colours.
  • a character restituted on a terminal with an extended gamut will have a particularly red face, which degrades the quality of the perception of the content to be restituted.
  • the invention proposes a new solution in the form of a method for obtaining images representative of a scene and for processing the images obtained.
  • such a method implements the following steps:
  • the first image obtaining at least one image representative of a scene, whose colours belong to a first colour gamut, called the first image
  • the method also comprises the transmission and/or the storage of the first image and the mask.
  • the invention is based on a new and inventive approach for processing a content to be restituted, with a view to its transmission and/or storage, based on the construction of a mask making it possible to identify, within a first image to be restituted, the regions which comprise colours which it is desirable to extend and the regions which comprise colours which it is desirable to leave unchanged during the restitution of the image on a terminal able to restitute a wider range of colours than that of the first gamut.
  • the mask constructed according to the invention can therefore be used by a restitution terminal capable of restituting colours in an extended gamut, such as the second gamut, during a step of extension/saturation of the colours of the first image to be restituted, from the first gamut to the second gamut.
  • the second gamut comprises the first gamut and at least one colour not belonging to the first gamut.
  • the step of extension is not implemented arbitrarily or globally, but optimally, by extending/saturating the colours only in regions "authorised" by the mask.
  • the transmission and/or storage of the mask and the first image representative of the scene to be restituted, whose colours belong to the first gamut is generally less costly in terms of resources than the transmission and/or storage of both the first image with the first gamut and the second image with the second gamut. Even by only stocking the first image with the first gamut and the mask, it is possible to restitute the scene in an extended gamut such as the second gamut, at least on a restitution device capable of restituting colours in this extended gamut.
  • the invention is notably adapted to the processing of standard video contents defined in a standard gamut, such as described in the ITU- BT.709 standard, and enables the transmission of additional information, in the form of the mask, enabling an optimised restitution of these items of content in an extended gamut.
  • the first gamut is the gamut of the Rec 709 colour space, as defined in the ITU-R BT.709 standard.
  • the first and second images are captured by distinct capture devices.
  • first device of standard still or video camera type for example making it possible to capture the first images
  • second device of still or video camera type making it possible to capture the second images, located in the same place and making it possible to capture the same scene.
  • the first device is capable of providing colours which are inside the first gamut, i.e. first images whose colours are inside the first gamut.
  • the second device is capable of providing colours which are inside the second gamut, i.e. second images whose colours are inside the second gamut.
  • the step of detection implements an algorithm for registration of the first and second images.
  • the first and second images are captured by a same device, by using two distinct settings of this device.
  • the step of obtaining at least one second image is implemented at predetermined instants and/or after obtaining a predetermined number of first images.
  • the method preferably comprises a step of updating the mask.
  • N an integer greater than or equal to 2
  • the mask is binary, a first value being associated with the regions of the second image whose colours belong to the first gamut and a second value being associated with the regions of the second image whose colours belong to the second gamut but do not belong to the first gamut.
  • Such a mask according to the invention therefore corresponds to a third image, which may be superimposed (for example by multiplication) with the first image during the restitution in order to define the regions of the first image wherein the colours can be extended.
  • the invention in another embodiment, relates to a device for obtaining images representative of a scene and for processing these images.
  • such a device also comprises:
  • a module for detecting the regions of the second image whose colours belong to the second gamut but do not belong to the first gamut a module for constructing a mask, corresponding to a third image identifying the detected regions.
  • the device also comprises a module for transmission and/or storage of the first image and the mask.
  • Such a device is notably adapted to implement the method for obtaining and processing images previously described. It is for example integrated into a transmitter or a head-end of a broadcasting system.
  • This device could of course comprise the different characteristics relating to the image processing method according to the invention, which may be combined or taken separately. Thus, the characteristics and advantages of this device are the same as those of the image processing method. Consequently, they are not detailed further.
  • the invention also relates to a method for restituting at least one image.
  • Such a method comprises the following steps:
  • the second colour gamut is therefore distinct from the first colour gamut.
  • Such a mask is thus configured to identify at least one region of the received image or images, also called the first images. More specifically, by applying such a mask to the received images, it is possible to select at least one region of the received image or images and to extend the colours of the received image or images only in the selected region or regions.
  • such a restitution method is adapted to receive a mask constructed by using an image processing method as described above. It therefore has the same characteristics and advantages as those of the processing method presented above. Consequently, they are not detailed further.
  • the invention in another embodiment, relates to a device for restitution of at least one image.
  • such a device comprises:
  • a module for applying the mask to the at least one image a module for extending the colours of the at least one image in the regions identified by application of the mask, delivering an image whose colours belong to a second colour gamut, and in which at least one colour does not belong to the first gamut.
  • the second colour gamut is therefore distinct from the first colour gamut.
  • Such a restitution device is notably adapted to implement the restitution method previously described. It is for example integrated into a terminal of a user (television set, computer, mobile telephone, tablet, etc.), possibly combined with a set-top box.
  • This device could of course comprise the different characteristics relating to the restitution method previously described, which may be combined or taken separately. Thus, the characteristics and advantages of this device are the same as those of the restitution method. Consequently, they are not detailed further.
  • the invention relates to one or more computer programs comprising instructions for implementing an image processing method and/or instructions for implementing a method for restituting at least one image as described above, when this or these programs are executed by a processor.
  • the methods according to the invention can therefore be implemented in various ways, notably in wired form or in software form.
  • the invention also relates to an image processing system comprising:
  • At least one image capture device able to capture at least one image representative of a scene whose colours belong to a first colour gamut, called the first image, and at least one image representative of said scene whose colours belong to a second colour gamut, called the second image, and in which at least one colour does not belong to the first gamut,
  • a device for obtaining and processing images comprising:
  • a device for restituting at least one image comprising:
  • the device for obtaining and processing images comprises a module for transmission and/or storage of the first image and the mask.
  • Such a system notably comprises an image processing device and an image restitution device as previously described.
  • image processing device notably comprises an image processing device and an image restitution device as previously described.
  • image restitution device as previously described.
  • the different characteristics of the present invention can be implemented in the form of a system, devices, methods or computer-readable media. Consequently, the different characteristics of the present invention can take the form of an entirely hardware embodiment, entirely software embodiment or an embodiment combining software and hardware aspects.
  • certain characteristics of the present invention can take the form of a computer-readable storage medium. Any combination of one or more computer-readable storage media can be used.
  • figure 1 shows the main steps implemented by an image processing method according to an embodiment of the invention
  • figure 2 shows the main steps implemented by an image restitution method according to an embodiment of the invention
  • FIG. 3 shows an image processing system according to a particular embodiment of the invention
  • FIGS. 4 and 5 show respectively the simplified structure of an image processing device and the simplified structure of an image restitution device according to a particular embodiment of the invention.
  • the general principle of the invention is based on the construction of a mask, during the creation of a content of image or video (succession of images) type or the transmission/broadcast of this content, making it possible to identify within an image of this content the regions composed of colours which it is worthwhile extending, i.e. for which it is possible to modify the colourimetry during restitution, so as to restitute these regions using a wider range of colours.
  • At least one image representative of a scene is obtained, whose colours belong to a first colour gamut, called the first image.
  • the first image captured at instant t is denoted l x (t).
  • a second step 12 at least one image representative of the same scene is obtained, with substantially the same viewpoint, whose colours belong to a second colour gamut, called the second image, this image here comprising at least one colour not belonging to the first gamut.
  • the second image captured at instant t is denoted l 2 (t).
  • the second gamut comprises the first gamut and the at least one colour not belonging to the first gamut.
  • the operations for capturing the first and second images at instant t are performed simultaneously.
  • the processing of these two images can be deferred.
  • the two obtaining steps 11 and 12 can correspond either to the actual capture of the first and second images, or to the receipt of the first and second images by an image processing device following the capture of the first and second images. These two obtaining steps 11 and 12 can therefore be implemented simultaneously or possibly one after the other.
  • a mask is constructed, corresponding to a third image l 3 (t) identifying the detected regions.
  • Such a mask is for example a binary mask, whose pixels take the value '0' in the regions corresponding to the regions of the second image whose colours belong to the first gamut (i.e. in the regions wherein the colours of the pixels are identical between the first and second image) and the value ⁇ in the regions corresponding to the regions of the second image whose colours belong to the second gamut but do not belong to the first gamut (i.e. in the regions wherein the colours of the pixels are different between the first and second image).
  • the first image (whose colours belong to the first gamut) and the mask can be transmitted and/or stored, in order to be able to restitute the first image and the second image, for example as specified later.
  • the main steps implemented by a restitution method according to an embodiment of the invention are shown in figure 2.
  • a first step 21 at least one first image representative of a scene is received, whose colours belong to a first colour gamut, and a mask configured to select at least one region of the image or images.
  • a mask configured to select at least one region of the image or images.
  • such a may have been constructed by using an image processing method as described above.
  • the first image li(t) and the third image l 3 (t), also called the mask are received.
  • the mask is applied to the first image.
  • the first and the third image are multiplied, so as to identify the regions of the first image whose colours can be extended.
  • a third step 23 of extension of colours the colours of the first image in the regions identified by application of the mask are extended.
  • a new image I is thus obtained whose colours belong to a second colour gamut and in which at least colour does not belong to the first gamut. If we consider the above example according to which the mask is a binary mask, the colours of the first image are extended in the regions of this image corresponding to the regions of the mask having a value equal to ⁇ and the colours of the first image are not extended in the regions of this image corresponding to the regions of the mask having a value equal to ⁇ '.
  • a scene 31 to be captured is for example composed of a character 310, a table 311 and a shrub 312.
  • Two capture devices 321 and 322 are considered positioned so as to capture the same scene 31, for example positioned one on top of the other.
  • a same capture device can be used to capture the first and second images.
  • a camera for example adapted to capture images having colours in a wide range is used, and the settings of this camera are modified to also capture images having colours in a standard range.
  • the first capture device 321 makes it possible to capture images whose colours belong to a first gamut.
  • the first capture device 321 is of broadcast camera type capable of providing an item of content whose colours belong to the first gamut, for example the gamut defined in the ITU-R BT.709 standard.
  • the second capture device 322 makes it possible to capture images whose colours belong to a second gamut, where the second gamut is wider than the first gamut (i.e. comprises at least one additional colour with respect to the range of colours of the first gamut).
  • the second capture device 322 is a sensor of still camera type.
  • the second capture device 322 may notably have a lower definition/spatial resolution than that of the first capture device 321.
  • the first capture device 321 can shoot continuously.
  • the flowers 3121 of the shrub 312 of the scene to be captured 31 have a red colour not belonging to the first gamut, but belonging to the second gamut.
  • the table 311 of the scene to be captured 31 has a yellow colour not belonging to the first gamut, but belonging to the second gamut.
  • the scene to be captured 31 therefore comprises elements whose colours belong to the first gamut, and elements whose colours do not belong to the first gamut.
  • the first capture device 321 makes it possible to capture the scene 31 with colours limited to the first gamut.
  • the colours associated with the flowers 3121 and the table 311 in the first image are therefore "degraded” by the first capture device 321.
  • the second capture device 322 makes it possible to capture the scene 31 with colours limited to the second gamut.
  • the colours associated with the flowers 3121 and the table 311 in the second image are therefore not “degraded” by the second capture device 322, if we assume that their colours in the actual scene are inside the second gamut.
  • such an image processing device comprises a first module 331, making it possible to obtain the first images and a second module 332 making it possible to obtain the second images.
  • Such an image processing device also comprises a detection module 333 which makes it possible to detect the regions of the second image whose colours belong to the second gamut but do not belong to the first gamut. In other words, the aim is to detect the regions of the second image which are outside the first gamut.
  • a module is also called an extended gamut detector.
  • the second image, obtained by photographing the scene 31 can be superimposed on the first image, obtained by filming the scene 31, in order to detect the regions of the second image whose colours belong to the second gamut but do not belong to the first gamut.
  • an algorithm of registration type is for example used, making it possible to match the pixels associated with two images.
  • Such an algorithm is notably presented in the document "Optimization of Sparse Color Correspondences for Color Mapping", S.F. Hasan, J. Stauder, A. Tremeau (20th Color Imaging Conference, November 2012, Los Angeles).
  • other image registration/alignment algorithms may be used within the scope of the invention. It is noted that in the case where the first and second images are captured by a same device, it is not necessary to align the two images before processing.
  • the image processing device also comprises a module for constructing a mask 334, corresponding to a third image identifying the detected regions.
  • the result of the extended gamut detector can be encoded in binary form.
  • Different techniques can be implemented to detect the regions of the second image which are outside the first gamut and construct a mask identifying the detected regions, using for example the characterisation files F of the capture devices used.
  • the manufacturer data (i.e. the characterisation file) of the first capture device are used to find out the gamut associated with the first capture device.
  • the XYZ of each pixel of the second image is calculated, and we look to see whether this XYZ is inside the first gamut. If it is, the corresponding pixel of the mask has a value of 0; if it is not, the corresponding pixel of the mask has a value of 1.
  • the mask therefore makes it possible to identify the flowers 3121 and the table 311, and corresponds to a third image wherein the pixels associated with the flowers 3121 and the table 311 take a value equal to '1' and the other pixels take a value equal to ' ⁇ '.
  • the mask is not necessarily binary and may also comprise grey levels, for example at the contours of objects (flowers 3121 and table 311).
  • the frequency of capturing the first and second images is not identical, and if several first images are captured for a second image, it is possible to update the mask. For example, it is considered that, at instant t, a first image and a second image are captured, denoted l a (t) and l 2 (t) respectively. At instant t+1, only a first image is captured, denoted li(t+l). At instant t+2, only a first image is captured, denoted li(t+2). At instant t+3, a first image and a second image are captured, denoted li(t+3) and l 2 (t+3) respectively.
  • a first mask l 3 (t) is for example calculated using the li(t)/l 2 (t) pair at instant t.
  • a mask notably makes it possible to identify zones and contours in the first image corresponding to the regions of the second image whose colours belong to the second gamut but do not belong to the first gamut, such as the flowers 3121 and the table 311 of the scene to be captured 31.
  • An object-tracking algorithm may be implemented on these zones/contours of the first image at instant t+1 and at instant t+2, so as to update the mask at instant t+1, denoted l 3 (t+l), and at instant t+2, denoted l 3 (t+2) by updating the corresponding zones/contours in the mask.
  • images li(t+3) and l 2 (t+3) are available.
  • the mask l 3 (t+3) can therefore be calculated directly using the li(t+3)/l 2 (t+3) pair.
  • the mask or masks can then be transmitted and/or stored with the first images by means of the transmission and/or storage module 335.
  • a restitution device 34 comprises a module for receiving 341 at least one mask and one first image, a module for applying 342 the mask to the first image and a module for extending the colours 343 of the first image in the regions identified by application of the mask, delivering an image I whose colours belong to a second colour gamut, also called an extended gamut, and in which at least one colour does not belong to the first gamut.
  • the module for applying 342 the mask makes it possible to superimpose a mask on a first image, and to identify within the first image the regions having colours which it is possible to extend (colour expansion).
  • This first image can be directly from the capture device, or have received initial processing aiming to bring the colours of the image inside the first gamut (for example the gamut of the colour space ec 709) or to perform a first rough grading.
  • the application module 342 would make it possible to identify the flowers 3121 and the table 311 as belonging to regions of the first image wherein it is possible to extend the colourimetry.
  • the application of the mask to the first image implements a multiplication of the first image by the mask.
  • the mask is a binary mask, having pixels coded by a ⁇ in the zones which are outside the first gamut, and by '0' elsewhere, after multiplication only the zones in which it is possible to apply the colour extension are obtained.
  • a same mask can potentially be applied to several first images.
  • the module for extending the colours 343 then implements a standard algorithm for extending the colours of the first image, only in the regions identified by application of the mask.
  • a standard algorithm for extending the colours of the first image, only in the regions identified by application of the mask.
  • such an algorithm is described in the document "Gamut Expansion for Video and Image Sets" (Hyrum Anderson, Eric K. Garcia and Maya R. Gupta).
  • other standard extension algorithms may be used within the scope of the invention.
  • the module for extending the colours 343 makes it possible to extend the colours of the flowers 3121 and the table 311 of the first image with colours belonging to the second gamut.
  • these colours have been modified to enter the first gamut during the capture of the scene by the first capture device, or during a processing operation to bring the colours of the image inside the first gamut (for example the gamut of the Rec 709 colour space) or to perform a first rough grading.
  • such an image processing device comprises a memory 41 comprising a buffer memory, a processing unit 42, equipped for example with a microprocessorjnP and controlled by the computer program 43, implementing the image processing method according to the invention.
  • the code instructions of the computer program 43 are for example loaded into a RAM memory before being executed by the processor of the processing unit 42.
  • the processing unit 42 receives at input at least one first image ⁇ 1 and at least one second image l 2 corresponding to a same scene.
  • the microprocessor of the processing unit 42 implements the steps of the image processing method previously described, according to the instructions of the computer program 43, to construct a mask l 3 .
  • the image processing device further comprises: a module 331 for obtaining at least one first image, a module 332 for obtaining at least one second image, a module for detecting 333 the regions of the second image whose colours belong to the second gamut but do not belong to the first gamut, a module for constructing 334 a mask and a module 335 for transmitting and/or storing the first image and the mask.
  • such a restitution device comprises a memory 51 comprising a buffer memory, a processing unit 52, equipped for example with a microprocessorjnP and controlled by the computer program 53, implementing the method for restituting at least one image previously described.
  • the code instructions of the computer program 53 are for example loaded into a RAM memory before being executed by the processor of the processing unit 52.
  • the processing unit 52 receives at input at least one mask and one first image.
  • the microprocessor of the processing unit 52 implements the steps of the restitution method previously described, according to the instructions of the computer program 53, in order to identify the regions of the first image having colours which it is possible to extend/saturate.
  • the restitution device further comprises: a module for receiving 341 a mask and at least one first image, a module for applying 342 the mask to the first image, a module for extending 343 the colours of the first image or images in the regions identified by application of the mask, delivering an image I whose colours belong to a second colour gamut.
  • These modules are controlled by the microprocessor of the processing unit 52.

Abstract

The invention relates to an image processing method, implementing a step of obtaining (11) at least one image representative of a scene, whose colours belong to a first colour gamut, called the first image. According to the invention, such a method implements the following steps: obtaining (12) at least one image representative of said scene, whose colours belong to a second colour gamut, called the second image, said second gamut comprising at least one colour not belonging to said first gamut, detecting (13) the regions of said second image whose colours belong to said second gamut but do not belong to said first gamut, constructing (14) a mask identifying said detected regions, transmitting and/or storing (15) said mask.

Description

IMAGE PROCESSING METHOD AND DEVICE, IMAGE RESTITUTION METHOD AND DEVICE, AND CORRESPONDING COMPUTER PROGRAM AND SYSTEM
1. Field of the invention
The field of the invention is that of image processing and restitution, and notably processing and restitution of a video stream comprising a succession of images.
More specifically, the invention relates to the colourimetry of the restituted images and proposes a technique making it possible to extend the colourimetry simply in certain regions of an image, that is to say to restitute the image using a wider range of colours in certain regions of the image.
The invention notably finds applications in the restitution of images on terminals which can display a wide range of colours, and more specifically in the restitution of HD (high dynamic range) images, or the restitution of WCG (wide colour gamut) images.
2. Prior art
The technologies used for the restitution/display of images have changed considerably. Thus, the use of technologies of OLED (organic light-emitting diode) type, LCD (liquid-crystal display) type, laser type, etc. enables the restitution of images over a wide range of colours, called an extended gamut.
However, the range of colours of the content to be restituted is often limited during the creation or the transmission of the content to be restituted. For example, when a video is constructed according to the ITU-R BT.709 standard, the images composing the video have colours belonging to a standard range of colours, called a standard gamut.
During restitution of such a content, having a standard gamut, on a terminal capable of restituting colours in an extended gamut, the colours of the content to be restituted are modified, in order to "extend" the colours of the content to be restituted to the extended gamut. To do this, the primary colours blue, red and green of the standard gamut of the content to be restituted and the primary colours blue, red and green of the extended gamut of the restitution terminal are matched, and the colour space defined between these two gamuts is extended.
This technique of extending colour gamuts is notably described in the document by J.
Morovic entitled "Digital Color Imaging Handbook" (chapter 10, pages 639-686 - CRC Press, Boca Raton, Florida 2003).
However, a disadvantage of this technique is that it performs a global extension of the whole of the image to be restituted, which notably leads to an oversaturation of flesh, pastel or neutral colours. Thus a character restituted on a terminal with an extended gamut will have a particularly red face, which degrades the quality of the perception of the content to be restituted.
There therefore exists a need for a new technique making it possible to adjust the colourimetry of an image/a succession of images, during the restitution of this image/succession of images on a terminal with an extended gamut.
3. Summary of the invention
The invention proposes a new solution in the form of a method for obtaining images representative of a scene and for processing the images obtained.
According to the invention, such a method implements the following steps:
obtaining at least one image representative of a scene, whose colours belong to a first colour gamut, called the first image,
obtaining at least one other image representative of said scene, whose colours belong to a second colour gamut, called the second image, said second image comprising at least one colour not belonging to the first gamut,
detecting the regions of the second image whose colours belong to the second gamut but do not belong to the first gamut,
constructing a mask, corresponding to a third image identifying the detected regions. Preferably, the method also comprises the transmission and/or the storage of the first image and the mask.
Thus, the invention is based on a new and inventive approach for processing a content to be restituted, with a view to its transmission and/or storage, based on the construction of a mask making it possible to identify, within a first image to be restituted, the regions which comprise colours which it is desirable to extend and the regions which comprise colours which it is desirable to leave unchanged during the restitution of the image on a terminal able to restitute a wider range of colours than that of the first gamut.
The mask constructed according to the invention can therefore be used by a restitution terminal capable of restituting colours in an extended gamut, such as the second gamut, during a step of extension/saturation of the colours of the first image to be restituted, from the first gamut to the second gamut. For example, the second gamut comprises the first gamut and at least one colour not belonging to the first gamut.
Thus, the step of extension is not implemented arbitrarily or globally, but optimally, by extending/saturating the colours only in regions "authorised" by the mask. Moreover, the transmission and/or storage of the mask and the first image representative of the scene to be restituted, whose colours belong to the first gamut, is generally less costly in terms of resources than the transmission and/or storage of both the first image with the first gamut and the second image with the second gamut. Even by only stocking the first image with the first gamut and the mask, it is possible to restitute the scene in an extended gamut such as the second gamut, at least on a restitution device capable of restituting colours in this extended gamut.
The invention is notably adapted to the processing of standard video contents defined in a standard gamut, such as described in the ITU- BT.709 standard, and enables the transmission of additional information, in the form of the mask, enabling an optimised restitution of these items of content in an extended gamut.
Thus, in a particular embodiment, the first gamut is the gamut of the Rec 709 colour space, as defined in the ITU-R BT.709 standard.
According to a particular characteristic of the invention, the first and second images are captured by distinct capture devices.
In this way, it is possible to use a first device of standard still or video camera type for example making it possible to capture the first images, and a second device of still or video camera type making it possible to capture the second images, located in the same place and making it possible to capture the same scene.
In other words, the first device is capable of providing colours which are inside the first gamut, i.e. first images whose colours are inside the first gamut. The second device is capable of providing colours which are inside the second gamut, i.e. second images whose colours are inside the second gamut.
According to this particular embodiment, the step of detection implements an algorithm for registration of the first and second images.
This notably makes it possible to match the images representative of the same scene obtained by distinct capture devices, and to obtain a mask of better quality.
According to a variant, the first and second images are captured by a same device, by using two distinct settings of this device.
In this way, it is possible to use a same device of still or video camera type for example, to capture the first and the second images. We are thus ensured of capturing the same scene, and the operation of alignment/registration of the images is optional. According to another specific aspect of the invention, the step of obtaining at least one second image is implemented at predetermined instants and/or after obtaining a predetermined number of first images.
In fact, it is not necessary for the number of first images and the number of second images to be identical. Insofar as the second images are captured by a device making it possible notably to capture images with a wide range of colours, the capture and/or storage of these second images is generally more costly. It is therefore intended, according to this aspect of the invention, that only one second image for example every 5, 10 or 20 first images, or one second image at each new sequence or new shot, is captured.
In particular, when the frequency of capturing the first and second images is distinct, the method preferably comprises a step of updating the mask.
Thus, in the case where a second image is captured for N first images, with N an integer greater than or equal to 2, it is possible to implement an object-tracking algorithm on regions of the first image identified by the mask, making it possible to update the mask.
In particular, the mask is binary, a first value being associated with the regions of the second image whose colours belong to the first gamut and a second value being associated with the regions of the second image whose colours belong to the second gamut but do not belong to the first gamut.
Such a mask according to the invention therefore corresponds to a third image, which may be superimposed (for example by multiplication) with the first image during the restitution in order to define the regions of the first image wherein the colours can be extended.
It is noted that the different characteristics of the image capture and processing method presented above may be combined.
In another embodiment, the invention relates to a device for obtaining images representative of a scene and for processing these images.
According to the invention, such a device also comprises:
a module for obtaining at least one image representative of said scene, whose colours belong to a first colour gamut, called the first image,
- a module for obtaining at least one image representative of said scene, whose colours belong to a second colour gamut, called the second image, said second image comprising at least one colour not belonging to the first gamut,
a module for detecting the regions of the second image whose colours belong to the second gamut but do not belong to the first gamut, a module for constructing a mask, corresponding to a third image identifying the detected regions.
Preferably, the device also comprises a module for transmission and/or storage of the first image and the mask.
Such a device is notably adapted to implement the method for obtaining and processing images previously described. It is for example integrated into a transmitter or a head-end of a broadcasting system.
This device could of course comprise the different characteristics relating to the image processing method according to the invention, which may be combined or taken separately. Thus, the characteristics and advantages of this device are the same as those of the image processing method. Consequently, they are not detailed further.
The invention also relates to a method for restituting at least one image.
Such a method comprises the following steps:
receiving a mask and at least one image representative of a scene, whose colours belong to a first colour gamut;
applying the mask to the at least one image;
extending the colours of the at least one image in the regions identified by the application of the mask, delivering an image whose colours belong to a second colour gamut, and in which at least one colour does not belong to said first gamut.
The second colour gamut is therefore distinct from the first colour gamut.
Such a mask is thus configured to identify at least one region of the received image or images, also called the first images. More specifically, by applying such a mask to the received images, it is possible to select at least one region of the received image or images and to extend the colours of the received image or images only in the selected region or regions.
In particular, such a restitution method is adapted to receive a mask constructed by using an image processing method as described above. It therefore has the same characteristics and advantages as those of the processing method presented above. Consequently, they are not detailed further.
In another embodiment, the invention relates to a device for restitution of at least one image.
According to the invention, such a device comprises:
a module for receiving a mask and at least one image representative of a scene, whose colours belong to a first colour gamut;
a module for applying the mask to the at least one image; a module for extending the colours of the at least one image in the regions identified by application of the mask, delivering an image whose colours belong to a second colour gamut, and in which at least one colour does not belong to the first gamut. The second colour gamut is therefore distinct from the first colour gamut.
Such a restitution device is notably adapted to implement the restitution method previously described. It is for example integrated into a terminal of a user (television set, computer, mobile telephone, tablet, etc.), possibly combined with a set-top box.
This device could of course comprise the different characteristics relating to the restitution method previously described, which may be combined or taken separately. Thus, the characteristics and advantages of this device are the same as those of the restitution method. Consequently, they are not detailed further.
In yet another embodiment, the invention relates to one or more computer programs comprising instructions for implementing an image processing method and/or instructions for implementing a method for restituting at least one image as described above, when this or these programs are executed by a processor.
The methods according to the invention can therefore be implemented in various ways, notably in wired form or in software form.
The invention also relates to an image processing system comprising:
at least one image capture device, able to capture at least one image representative of a scene whose colours belong to a first colour gamut, called the first image, and at least one image representative of said scene whose colours belong to a second colour gamut, called the second image, and in which at least one colour does not belong to the first gamut,
a device for obtaining and processing images comprising:
a module for obtaining the first image,
a module for obtaining the second image,
a module for detecting the regions of the second image whose colours belong to the second gamut but do not belong to the first gamut,
a module for constructing a mask, corresponding to a third image identifying the detected regions, and
a device for restituting at least one image comprising:
a module for receiving the mask and the first image;
a module for applying the mask to the first image;
a module for extending the colours of the first image in the regions identified by application of the mask, delivering an image whose colours belong to a second colour gamut, and in which at least one colour does not belong to said first gamut.
Preferably, the device for obtaining and processing images comprises a module for transmission and/or storage of the first image and the mask.
Such a system notably comprises an image processing device and an image restitution device as previously described. Thus, the characteristics and advantages of this device are the same as those described above.
The different characteristics of the present invention can be implemented in the form of a system, devices, methods or computer-readable media. Consequently, the different characteristics of the present invention can take the form of an entirely hardware embodiment, entirely software embodiment or an embodiment combining software and hardware aspects.
Moreover, certain characteristics of the present invention can take the form of a computer-readable storage medium. Any combination of one or more computer-readable storage media can be used.
4. List of figures
Other characteristics and advantages of the invention will emerge more clearly upon reading the following description of a particular embodiment, provided as a simple non- restrictive example and referring to the annexed drawings, wherein:
figure 1 shows the main steps implemented by an image processing method according to an embodiment of the invention;
figure 2 shows the main steps implemented by an image restitution method according to an embodiment of the invention;
- figure 3 shows an image processing system according to a particular embodiment of the invention;
figures 4 and 5 show respectively the simplified structure of an image processing device and the simplified structure of an image restitution device according to a particular embodiment of the invention.
5. Description of an embodiment of the invention
5.1 General principle
The general principle of the invention is based on the construction of a mask, during the creation of a content of image or video (succession of images) type or the transmission/broadcast of this content, making it possible to identify within an image of this content the regions composed of colours which it is worthwhile extending, i.e. for which it is possible to modify the colourimetry during restitution, so as to restitute these regions using a wider range of colours.
We show, in relation to figure 1, the main steps implemented by a method for obtaining and processing images according to an embodiment of the invention.
During a first step 11, at least one image representative of a scene is obtained, whose colours belong to a first colour gamut, called the first image. The first image captured at instant t is denoted lx(t).
During a second step 12, at least one image representative of the same scene is obtained, with substantially the same viewpoint, whose colours belong to a second colour gamut, called the second image, this image here comprising at least one colour not belonging to the first gamut. The second image captured at instant t is denoted l2(t). For example, the second gamut comprises the first gamut and the at least one colour not belonging to the first gamut.
It is noted that the operations for capturing the first and second images at instant t are performed simultaneously. However, the processing of these two images can be deferred. As a result, the two obtaining steps 11 and 12 can correspond either to the actual capture of the first and second images, or to the receipt of the first and second images by an image processing device following the capture of the first and second images. These two obtaining steps 11 and 12 can therefore be implemented simultaneously or possibly one after the other.
At the end of these obtaining steps 11 and 12, during a third step 13 the regions of the second image whose colours belong to the second gamut but do not belong to the first gamut are detected.
During a fourth step 14, a mask is constructed, corresponding to a third image l3(t) identifying the detected regions.
Such a mask is for example a binary mask, whose pixels take the value '0' in the regions corresponding to the regions of the second image whose colours belong to the first gamut (i.e. in the regions wherein the colours of the pixels are identical between the first and second image) and the value Ύ in the regions corresponding to the regions of the second image whose colours belong to the second gamut but do not belong to the first gamut (i.e. in the regions wherein the colours of the pixels are different between the first and second image).
During a fifth optional step 15, the first image (whose colours belong to the first gamut) and the mask can be transmitted and/or stored, in order to be able to restitute the first image and the second image, for example as specified later. The main steps implemented by a restitution method according to an embodiment of the invention are shown in figure 2.
During a first step 21, at least one first image representative of a scene is received, whose colours belong to a first colour gamut, and a mask configured to select at least one region of the image or images. In particular, such a may have been constructed by using an image processing method as described above. For example, at a given instant, the first image li(t) and the third image l3(t), also called the mask, are received.
During a second step 22, the mask is applied to the first image. In other words, the first and the third image are multiplied, so as to identify the regions of the first image whose colours can be extended.
During a third step 23 of extension of colours, the colours of the first image in the regions identified by application of the mask are extended. A new image I is thus obtained whose colours belong to a second colour gamut and in which at least colour does not belong to the first gamut. If we consider the above example according to which the mask is a binary mask, the colours of the first image are extended in the regions of this image corresponding to the regions of the mask having a value equal to Ύ and the colours of the first image are not extended in the regions of this image corresponding to the regions of the mask having a value equal to Ό'.
If we consider a scene with a character and a set constituted of a blue sky and a yellow sun, it is thus possible according to the invention to restitute a more brilliant sun and a brighter sky by using a wider range of colours, corresponding to the second gamut, without modifying the skin tone of the character. 5.2 Description of a particular embodiment
A description is given below of a particular embodiment of the invention, according to which two distinct capture devices are used to capture the first and second images during the creation of an item of content of image or video type.
As shown in figure 3, a scene 31 to be captured is for example composed of a character 310, a table 311 and a shrub 312. Two capture devices 321 and 322 are considered positioned so as to capture the same scene 31, for example positioned one on top of the other. It is recalled that, in a variant, a same capture device can be used to capture the first and second images. In this case, a camera for example adapted to capture images having colours in a wide range is used, and the settings of this camera are modified to also capture images having colours in a standard range.
The first capture device 321 makes it possible to capture images whose colours belong to a first gamut. For example, the first capture device 321 is of broadcast camera type capable of providing an item of content whose colours belong to the first gamut, for example the gamut defined in the ITU-R BT.709 standard. The second capture device 322 makes it possible to capture images whose colours belong to a second gamut, where the second gamut is wider than the first gamut (i.e. comprises at least one additional colour with respect to the range of colours of the first gamut). For example, the second capture device 322 is a sensor of still camera type. The second capture device 322 may notably have a lower definition/spatial resolution than that of the first capture device 321. Moreover, it can perform a restricted quantity of captures/shots with respect to the first capture device 321 which can shoot continuously. Thus, it is possible to capture only one second image every 5, 10 or 20 first images, or to capture one second image at each new sequence or new shot. It is also possible to capture a first image and a second image simultaneously, in order to obtain the same number of first images and second images.
For example, it is considered that the flowers 3121 of the shrub 312 of the scene to be captured 31 have a red colour not belonging to the first gamut, but belonging to the second gamut. Similarly, it is considered that the table 311 of the scene to be captured 31 has a yellow colour not belonging to the first gamut, but belonging to the second gamut. The scene to be captured 31 therefore comprises elements whose colours belong to the first gamut, and elements whose colours do not belong to the first gamut.
The first capture device 321 makes it possible to capture the scene 31 with colours limited to the first gamut. The colours associated with the flowers 3121 and the table 311 in the first image are therefore "degraded" by the first capture device 321. However, the second capture device 322 makes it possible to capture the scene 31 with colours limited to the second gamut. The colours associated with the flowers 3121 and the table 311 in the second image are therefore not "degraded" by the second capture device 322, if we assume that their colours in the actual scene are inside the second gamut.
These images are then transmitted to an image processing device 33, implementing the steps previously described to construct a mask.
More specifically, as shown in figure 3, such an image processing device comprises a first module 331, making it possible to obtain the first images and a second module 332 making it possible to obtain the second images. Such an image processing device also comprises a detection module 333 which makes it possible to detect the regions of the second image whose colours belong to the second gamut but do not belong to the first gamut. In other words, the aim is to detect the regions of the second image which are outside the first gamut. Such a module is also called an extended gamut detector.
Taking the above example, the second image, obtained by photographing the scene 31, can be superimposed on the first image, obtained by filming the scene 31, in order to detect the regions of the second image whose colours belong to the second gamut but do not belong to the first gamut. To do this, an algorithm of registration type is for example used, making it possible to match the pixels associated with two images. Such an algorithm is notably presented in the document "Optimization of Sparse Color Correspondences for Color Mapping", S.F. Hasan, J. Stauder, A. Tremeau (20th Color Imaging Conference, November 2012, Los Angeles). Naturally, other image registration/alignment algorithms may be used within the scope of the invention. It is noted that in the case where the first and second images are captured by a same device, it is not necessary to align the two images before processing.
The image processing device also comprises a module for constructing a mask 334, corresponding to a third image identifying the detected regions. In this module, the result of the extended gamut detector can be encoded in binary form.
Different techniques can be implemented to detect the regions of the second image which are outside the first gamut and construct a mask identifying the detected regions, using for example the characterisation files F of the capture devices used.
For example, if we take the context of a CIE XYZ colourimetric system, it is possible to perform a conversion of the output signal of the first capture device of camera type 321 into an XYZ signal, which will correspond to the XYZ of the scene, using the output signal of the camera 321 (for example an output signal of RGB type) and the characterisation file of the camera 321 (provided by the manufacturer), within the limits of the capability of the camera
321.
Similarly, it is possible to obtain the XYZ of the scene captured by the second capture device 322.
If the two capture devices are capable of perfectly restituting the XYZs of the scene, then we will have
XYZ (scene) = X^ Z (first capture device 321)
= X2Y2Z2 (second capture device 322). According to a first example, the manufacturer data (i.e. the characterisation file) of the first capture device are used to find out the gamut associated with the first capture device.
The XYZ of each pixel of the second image is calculated, and we look to see whether this XYZ is inside the first gamut. If it is, the corresponding pixel of the mask has a value of 0; if it is not, the corresponding pixel of the mask has a value of 1.
According to a second example, for each pixel of the first image, the corresponding vector of the first image Vt = X1Y1Z1 is compared with the corresponding vector of the second image after registration, V2 = X2Y2^2- If ^2 ~~ I S greater than a certain threshold, the corresponding pixel of the mask will be set to 1, otherwise it will be set to 0.
Thus, taking the above example, the mask therefore makes it possible to identify the flowers 3121 and the table 311, and corresponds to a third image wherein the pixels associated with the flowers 3121 and the table 311 take a value equal to '1' and the other pixels take a value equal to 'Ο'.
Naturally, the mask is not necessarily binary and may also comprise grey levels, for example at the contours of objects (flowers 3121 and table 311).
Moreover, if the frequency of capturing the first and second images is not identical, and if several first images are captured for a second image, it is possible to update the mask. For example, it is considered that, at instant t, a first image and a second image are captured, denoted la(t) and l2(t) respectively. At instant t+1, only a first image is captured, denoted li(t+l). At instant t+2, only a first image is captured, denoted li(t+2). At instant t+3, a first image and a second image are captured, denoted li(t+3) and l2(t+3) respectively.
In this case, a first mask l3(t) is for example calculated using the li(t)/l2(t) pair at instant t. Such a mask notably makes it possible to identify zones and contours in the first image corresponding to the regions of the second image whose colours belong to the second gamut but do not belong to the first gamut, such as the flowers 3121 and the table 311 of the scene to be captured 31.
An object-tracking algorithm may be implemented on these zones/contours of the first image at instant t+1 and at instant t+2, so as to update the mask at instant t+1, denoted l3(t+l), and at instant t+2, denoted l3(t+2) by updating the corresponding zones/contours in the mask. At instant t+3, images li(t+3) and l2(t+3) are available. The mask l3(t+3) can therefore be calculated directly using the li(t+3)/l2(t+3) pair.
The mask or masks can then be transmitted and/or stored with the first images by means of the transmission and/or storage module 335.
The restitution of the scene can then be implemented by a restitution device 34. More specifically, as shown in figure 3, such a restitution device 34 comprises a module for receiving 341 at least one mask and one first image, a module for applying 342 the mask to the first image and a module for extending the colours 343 of the first image in the regions identified by application of the mask, delivering an image I whose colours belong to a second colour gamut, also called an extended gamut, and in which at least one colour does not belong to the first gamut.
The module for applying 342 the mask makes it possible to superimpose a mask on a first image, and to identify within the first image the regions having colours which it is possible to extend (colour expansion). This first image can be directly from the capture device, or have received initial processing aiming to bring the colours of the image inside the first gamut (for example the gamut of the colour space ec 709) or to perform a first rough grading.
Thus, taking the above example, the application module 342 would make it possible to identify the flowers 3121 and the table 311 as belonging to regions of the first image wherein it is possible to extend the colourimetry.
For example, the application of the mask to the first image implements a multiplication of the first image by the mask. If the mask is a binary mask, having pixels coded by a Ύ in the zones which are outside the first gamut, and by '0' elsewhere, after multiplication only the zones in which it is possible to apply the colour extension are obtained.
According to a variant, a same mask can potentially be applied to several first images. The module for extending the colours 343 then implements a standard algorithm for extending the colours of the first image, only in the regions identified by application of the mask. For example, such an algorithm is described in the document "Gamut Expansion for Video and Image Sets" (Hyrum Anderson, Eric K. Garcia and Maya R. Gupta). Naturally, other standard extension algorithms may be used within the scope of the invention.
Again taking the example above, the module for extending the colours 343 makes it possible to extend the colours of the flowers 3121 and the table 311 of the first image with colours belonging to the second gamut.
It is thus possible to restitute the flowers 3121 and the table 311 with colours belonging to the second gamut, while the rest of the first image is restituted with colours belonging to the first gamut. In this way, the colours of the character 310, which belong to the first gamut (regardless of the capture device used) are restituted in the first gamut, and not in the second gamut, even if the restitution device is able to restitute colours in the second gamut. In other words, no colour extension is implemented for the colours of the scene to be captured belonging to the first gamut. The colour extension is implemented only for the colours of the scene to be captured belonging to the second gamut but not belonging to the first gamut. It is noted that these colours have been modified to enter the first gamut during the capture of the scene by the first capture device, or during a processing operation to bring the colours of the image inside the first gamut (for example the gamut of the Rec 709 colour space) or to perform a first rough grading.
The use of a mask, which can be constructed as previously described in relation to the image processing method or constructed in any other manner enabling the selection of different regions within an image, therefore makes it possible to adapt the colour extension algorithm implemented by a restitution device able to restitute colours in an extended gamut, by authorising colour extension only in certain regions of the image. An oversaturation of the colours of the character 310 is therefore notably avoided.
The resultant image can then be restituted on a screen of such a restitution device. 5.3 Simplified structures of the image processing and restitution devices
Finally, in relation to figures 4 and 5 respectively, the simplified structure of an image processing device implementing a technique for obtaining and processing images according to a particular embodiment of the invention and the structure of a restitution device implementing a technique for restituting at least one image according to a particular embodiment of the invention are presented.
As shown in figure 4, such an image processing device comprises a memory 41 comprising a buffer memory, a processing unit 42, equipped for example with a microprocessorjnP and controlled by the computer program 43, implementing the image processing method according to the invention.
At initialisation, the code instructions of the computer program 43 are for example loaded into a RAM memory before being executed by the processor of the processing unit 42. The processing unit 42 receives at input at least one first image \1 and at least one second image l2 corresponding to a same scene. The microprocessor of the processing unit 42 implements the steps of the image processing method previously described, according to the instructions of the computer program 43, to construct a mask l3. For this purpose, the image processing device further comprises: a module 331 for obtaining at least one first image, a module 332 for obtaining at least one second image, a module for detecting 333 the regions of the second image whose colours belong to the second gamut but do not belong to the first gamut, a module for constructing 334 a mask and a module 335 for transmitting and/or storing the first image and the mask.
These modules are controlled by the microprocessor of the processing unit 42. As shown in figure 5, such a restitution device according to a particular embodiment of the invention comprises a memory 51 comprising a buffer memory, a processing unit 52, equipped for example with a microprocessorjnP and controlled by the computer program 53, implementing the method for restituting at least one image previously described.
At initialisation, the code instructions of the computer program 53 are for example loaded into a RAM memory before being executed by the processor of the processing unit 52. The processing unit 52 receives at input at least one mask and one first image. The microprocessor of the processing unit 52 implements the steps of the restitution method previously described, according to the instructions of the computer program 53, in order to identify the regions of the first image having colours which it is possible to extend/saturate. For this purpose, the restitution device further comprises: a module for receiving 341 a mask and at least one first image, a module for applying 342 the mask to the first image, a module for extending 343 the colours of the first image or images in the regions identified by application of the mask, delivering an image I whose colours belong to a second colour gamut.
These modules are controlled by the microprocessor of the processing unit 52.

Claims

1. Method for obtaining images representative of a scene and for processing these images, comprising:
- obtaining (11) at least one image representative of said scene, called the first image, whose colours belong to a first colour gamut,
obtaining (12) at least one other image representative of said scene, whose colours belong to a second colour gamut, called the second image, said second image comprising at least one colour not belonging to said first gamut,
- detecting (13) the regions of said second image whose colours belong to said second gamut but do not belong to said first gamut,
constructing (14) a mask, corresponding to a third image identifying said detected regions.
2. Method for obtaining images of a scene and for processing these images according to claim 1, comprising the transmission and/or storage (15) of said first image and said mask.
3. Method for obtaining images of a scene and for processing these images according to claim 1 or 2, characterised in that said first and second images are captured by distinct capture devices.
4. Method for obtaining images of a scene and for processing these images according to claim 3, characterised in that said detection step (13) implements an algorithm for registration of said first and second images.
5. Method for obtaining images of a scene and for processing these images according to claim 1 or 2, characterised in that said first and second images are captured by a same capture device, by using two distinct settings of this capture device.
6. Method for obtaining images of a scene and for processing these images according to any one of claims 1 to 5, characterised in that said step of obtaining (12) at least one second image is implemented at predetermined instants and/or after obtaining a predetermined number of first images.
7. Method for restituting at least one image, characterised in that it comprises the following steps:
receiving (21) a mask and at least one image representative of a scene, whose colours belong to a first colour gamut;
- applying (22) the mask to the at least one image;
extending (23) the colours of the at least one image in the regions identified by the application (22) of said mask, delivering an image whose colours belong to a second colour gamut distinct from the first colour gamut, and in which at least one colour does not belong to said first gamut.
8. Device for obtaining images representative of a scene and for processing these images, comprising:
a module for obtaining (331) at least one image representative of said scene, whose colours belong to a first colour gamut, called the first image,
- a module for obtaining (332) at least one image representative of said scene, whose colours belong to a second colour gamut, called the second image, said second image comprising at least one colour not belonging to said first gamut,
a module for detecting (333) the regions of said second image whose colours belong to said second gamut but do not belong to said first gamut,
- a module for constructing (334) a mask, corresponding to a third image identifying said detected regions.
Device for restituting at least one image, characterised in that it comprises:
a module for receiving (341) a mask and at least one image representative of a scene, whose colours belong to a first colour gamut;
a module for applying (342) said mask to the at least one image;
a module for extending (343) the colours of the at least one image in the regions identified by application of said mask, delivering an image whose colours belong to a second colour gamut distinct from the first colour gamut, and in which at least one colour does not belong to said first gamut.
10. Computer program comprising instructions for the implementation of a method according to claim 1 or according to claim 7 when this program is executed by a processor. Image processing system comprising:
at least one image capture device (321, 322), able to capture at least one image representative of a scene whose colours belong to a first colour gamut, called the first image, and at least one image representative of said scene whose colours belong to a second colour gamut, called the second image, and in which at least one colour does not belong to said first gamut,
a device for obtaining and processing images (33) comprising:
a module for obtaining (331) said first image,
a module for obtaining (332) said second image,
a module for detecting (333) the regions of said second image whose colours belong to said second gamut but do not belong to said first gamut, a module for constructing (334) a mask, corresponding to a third image identifying said detected regions, and
a device for restituting (34) at least one image comprising:
a module for receiving (341) said mask and said first image;
a module for applying (342) said mask to said first image;
a module for extending the colours (343) of said first image in the regions identified by application of said mask, delivering an image whose colours belong to the second colour gamut, and in which at least one colour does not belong to said first gamut.
PCT/EP2014/067102 2013-08-12 2014-08-08 Image processing method and device, image restitution method and device, and corresponding computer program and system WO2015022274A1 (en)

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US20040131249A1 (en) * 2001-05-04 2004-07-08 Barry Sandrew Image sequence enhancement system and method
EP1294178A2 (en) * 2001-09-14 2003-03-19 Canon Kabushiki Kaisha Profile adjustment method, apparatus, and program
US20080158281A1 (en) * 2006-12-27 2008-07-03 Canon Kabushiki Kaisha Image forming apparatus and control method thereof
US20130135635A1 (en) * 2011-11-24 2013-05-30 Satoshi Nakamura Image processing apparatus, image processing system, and image processing method

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