IMPROVED HDR IMAGE ENCODING AND DECODING METHODS AND DEVICES

• US 20150358646A1
• Filed: 02/07/2014
• Published: 12/10/2015
• Est. Priority Date: 02/21/2013
• Status: Active Grant

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Koninklijke Philips N.V.
• Inventors: MERTENS, Mark Jozef Willem
• Granted Patent: US 9,699,482 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06T 2207/10024 Color image
• CPC Class Codes: G06T 2207/20092 Interactive image processing based on input by user
• CPC Class Codes: G06T 2207/20208 High dynamic range [HDR] image processing
• CPC Class Codes: G06T 5/92 based on global image properties
• CPC Class Codes: H04N 1/6058 Reduction of colour to a range of reproducible colours, e.g. to ink- reproducible colour gamut
• CPC Class Codes: H04N 1/64 Systems for the transmission or the storage of the colour picture signal; Details therefor, e.g. coding or decoding means therefor H04N19/00 takes precedence
• CPC Class Codes: H04N 19/186 the unit being a colour or a chrominance component
• CPC Class Codes: H04N 19/44 Decoders specially adapted therefor, e.g. video decoders which are asymmetric with respect to the encoder
• CPC Class Codes: H04N 19/98 Adaptive-dynamic-range coding [ADRC]
• CPC Class Codes: H04N 5/20 Circuitry for controlling amplitude response
• CPC Class Codes: H04N 9/68 for controlling the amplitude of colour signals, e.g. automatic chroma control circuits H04N9/71, H04N9/73 take precedence; camera processing pipelines for controlling the colour saturation of colour signals H04N23/86

Abstract

To allow graders to make optimally looking content of HDR scenes for various rendering displays, we invented an image encoder (202) comprising: an input (240) for a high dynamic range input image (M_HDR); an image grading unit (201) arranged to allow a human color grader to specify a color mapping from a representation (HDR_REP) of the high dynamic range input image defined according to a predefined accuracy, to a low dynamic range image (Im_LDR) by means of a human-determined color mapping algorithm, and arranged to output data specifying the color mapping (Fi(MP_DH)); and an automatic grading unit (203) arranged to derive a second low dynamic range image (GT_IDR) by applying an automatic color mapping algorithm to one of the high dynamic range input image (M_HDR) or the low dynamic range image (Im_LDR). We also describe and interesting new saturation processing strategy useful in the newly emerging high dynamic range image handling technology.

Claims

1. An image encoder comprising:

an input for a high dynamic range input image;

an image grading unit arranged to allow a human color grader to specify a color mapping from a representation of the high dynamic range input image, to a low dynamic range image by means of a human-determined color mapping algorithm, and arranged to output data specifying the color mapping; and

an automatic grading unit arranged to derive a second low dynamic range image by applying an automatic color mapping algorithm to the high dynamic range input image, with a color mapping algorithm fulfilling a condition that a HDR reconstructed image falling within a second predefined accuracy from the high dynamic range input image can be calculated by applying a second color mapping algorithm which is the inverse of the automatic color mapping algorithm to the second low dynamic range image.

2. An image encoder as claimed in claim 1, arranged to use as the representation the high dynamic range input image or the second low dynamic range image.

4. An image encoder as claimed in claim 1 in which the image grading unit and the automatic grading unit are arranged to apply a monotonous mapping function on a luminance-correlate of pixels in their respective input image, in at least a geometrical region of the respective input image corresponding to a same geometrical region of the high dynamic range input image.

6. An image encoder as claimed in claim 4, in which the automatic grading unit is arranged to determine the monotonous mapping function from luminance-correlates of pixels of the high dynamic range input image to luminance-correlates of pixels of the second low dynamic range image according to a criterion which determines respective ranges of luminance-correlates of pixels of the high dynamic range input image allocated to respective single values of a luminance-correlate of pixels of the second low dynamic range image, the respective ranges forming a set of luminance-correlate ranges covering the total range of possible luminance-correlate values for the high dynamic range input image.

7. An image encoder as claimed in claim 1, comprising a data formatter arranged to output into an image signal the second low dynamic range image and at least one of, or both of, data describing the color mapping between the high dynamic range input image and the second low dynamic range image, and data describing the color mapping between the low dynamic range image and the second low dynamic range image.

9. An image decoder as claimed in claim 6, comprising a system configuration unit, arranged to determine whether the decoder is connected to at least one of a high dynamic range display and a low dynamic range display, and the system configuration unit being arranged to configure the image derivation unit to determine at least the reconstruction in case of a connection to the high dynamic range display, and arranged to configure the image derivation unit to determine at least the low dynamic range image in case of a connection to the low dynamic range display.

10. An image decoder as claimed in claim 6 having as an output a wired connection or a wireless connection to any connectable display, and a signal formatter arranged to transmit at least one or both of the reconstruction and the low dynamic range image to any connected display.

11. An image decoder as claimed in claim 6, in which the image derivation unit is arranged to determine a further image based on the reconstruction and the low dynamic range image, or the second low dynamic range image and data describing the first color mapping and data describing the second color mapping.

12. An image decoder as claimed in claim 6 in which the image signal input is connected to a reading unit arranged to read the image signal from a memory object, such as e.g. a blu-ray disk.

13. An image decoder as claimed in claim 6 in which the image signal input is connectable to a network connection to a source of an image signal.

3. (canceled)

5. (canceled)

8. An image decoder arranged to receive via an image signal input an image signal comprising a second low dynamic range image, and data describing a first color mapping enabling reconstruction of a reconstruction of a high dynamic range image on the basis of the second low dynamic range image, and data describing a second color mapping allowing calculation of a low dynamic range image on the basis of the second low dynamic range image, the image decoder comprising an image derivation unit arranged to derive at least the low dynamic range image on the basis of the data describing the second color mapping and the pixel colors encoded in the second low dynamic range image.

14-15. -15. (canceled)

16. An image signal comprising a second low dynamic range image, and data describing a first color mapping enabling reconstruction of a reconstruction of a high dynamic range on the basis of the second low dynamic range image, and data describing a second color mapping allowing calculation of a low dynamic range image on the basis of the second low dynamic range image.

17. A memory object such as e.g. a blu-ray disk storing an image signal as claimed in claim 16.

18-21. -21. (canceled)