APPARATUS AND METHOD FOR DYNAMIC RANGE TRANSFORMING OF IMAGES

• US 20140210847A1
• Filed: 09/20/2012
• Published: 07/31/2014
• Est. Priority Date: 09/27/2011
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips N.V.
• Inventors: Knibbeler, Charles Leonardus Cornelius Maria, Van Der Vleuten, Renatus Josephus, De Haan, Wiebe
• Granted Patent: US 11,640,656 B2
• Time in Patent Office: Days
• US Class Current: 345/589
• CPC Class Codes: G06T 11/001 Texturing; Colouring; Generation of texture or colour inpainting G06T5/77
• CPC Class Codes: G06T 2207/20208 High dynamic range [HDR] image processing
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction
• CPC Class Codes: G06T 5/92 based on global image properties
• CPC Class Codes: G09G 2320/0271 Adjustment of the gradation levels within the range of the gradation scale, e.g. by redistribution or clipping
• CPC Class Codes: G09G 2320/0606 Manual adjustment
• CPC Class Codes: G09G 2320/0613 The adjustment depending on the type of the information to be displayed
• CPC Class Codes: G09G 2320/066 for control of contrast
• CPC Class Codes: G09G 2340/06 Colour space transformation
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 2370/047 using display data channel standard [DDC] communication
• CPC Class Codes: G09G 3/2003 Display of colours specific for liquid crystal displays G09G3/3607
• CPC Class Codes: G09G 5/006 Details of the interface to the display terminal specific for a display terminal using a CRT G09G1/167; using a flat panel G09G3/2096; circuits for interfacing with colour displays G09G5/04
• CPC Class Codes: G09G 5/10 Intensity circuits
• CPC Class Codes: G11B 20/10 Digital recording or reproducing
• CPC Class Codes: G11B 27/105 of operating discs
• CPC Class Codes: G11B 27/329 on a disc [VTOC]
• CPC Class Codes: H04N 7/00 Television systems details H04N3/00, H04N5/00; methods or arrangements, for coding, decoding, compressing or decompressing digital video signals H04N19/00; selective content distribution H04N21/00
• 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

An image processing apparatus comprises a receiver (201) for receiving an image signal which comprises at least an encoded image and a target display reference. The target display reference is indicative of a dynamic range of a target display for which the encoded image is encoded. A dynamic range processor (203) generates an output image by applying a dynamic range transform to the encoded image in response to the target display reference. An output (205) then outputs an output image signal comprising the output image, e.g. to a suitable display. The dynamic range transform may furthermore be performed in response to a display dynamic range indication received from a display. The invention may be used to generate an improved High Dynamic Range (HDR) image from e.g. a Low Dynamic Range (LDR) image, or vice versa.

Claims

1. An image processing apparatus comprising:

a receiver for receiving an image signal, the image signal comprising at least a first encoded image and a first target display reference, the first target display reference being indicative of a dynamic range of a first target display for which the first encoded image is encoded, the first target display reference comprising at least a white point luminance of the first target display, and the receiver being arranged to handle white point luminances of at least 1000 nits and the first encoded image corresponding therewith;

a dynamic range processor arranged to generate an output image by applying a dynamic range transform to the first encoded image taking into account the first target display reference; and

an output for outputting an output image signal comprising the output image.

3. The image processing apparatus of claim 1 wherein the first target display reference comprises an Electro Optical Transfer Function indication for the first target display.

4. The image processing apparatus of claim 1 wherein the first target display reference comprises a tone mapping indication representing a tone mapping used to generate the first encoded image for the first target display.

5. The image processing apparatus of claim 1 wherein the image signal further comprises a data field comprising dynamic range transform control data;

and wherein the dynamic range processor is further arranged to perform the dynamic range transform in response to the dynamic range transform control data.

6. The image processing apparatus of claim 1, wherein the dynamic range processor is arranged to detect the first encoded image being an LDR image encoded as a legacy LDR 8 or 10 bit encoding, is arranged to read from metadata associated with the image signal a dynamic range transform corresponding to the first target display reference, and is arranged to generate the output image being a high dynamic range image graded for rendering on the first target display by applying the dynamic range transform to the first encoded image.

7. The image processing apparatus of claim 5 wherein the dynamic range transform control data comprises different dynamic range transform parameters for different display maximum luminance levels.

8. The image processing apparatus of claim 5 wherein the dynamic range transform control data comprises different tone mapping parameters for different display maximum luminance levels, and wherein the dynamic range processor is arranged to determine tone mapping parameters for the dynamic range transform in response to the different tone mapping parameters and a maximum luminance for the output image signal.

9. The image processing apparatus of claim 5 wherein the dynamic range transform control data comprises data defining a set of transform parameters that must be applied by the dynamic range transform.

10. The image processing apparatus of claim 5 wherein the dynamic range transform control data comprises data defining limits for transform parameters to be applied by the dynamic range transform.

11. The image processing apparatus of claim 5 wherein the dynamic range transform control data comprises different transform control data for different image categories.

13. The image processing apparatus of claim 1 wherein the image signal comprises a second encoded image and a second target display reference, the second target display reference being indicative of a dynamic range of a second target display for which the second encoded image is encoded, the dynamic range of the second target display being different than the dynamic range of the first target display;

and

wherein the dynamic range processor is arranged to apply the dynamic range transform to the second encoded image in response to the second target display reference.

14. The image processing apparatus of claim 13 wherein the image dynamic range processor is arranged to generate the output image by combining the first encoded image and the second encoded image.

15. The image processing apparatus of claim 1 further comprising:

a receiver for receiving a data signal from a display, the data signal comprising a data field which comprises a display dynamic range indication of the display, the display dynamic range indication comprising at least one luminance specification; and

wherein

the dynamic range processor is arranged to apply the dynamic range transform to the first encoded image in response to the display dynamic range indication.

16. The image processing apparatus of claim 1 wherein the dynamic range processor is arranged to select between generating the output image as the first encoded image and generating the output image as a transformed image of the first encoded image in response to the first target display reference.

17. The image processing apparatus of claim 1 wherein the dynamic range transform comprises a gamut transform.

18. The image processing apparatus of claim 1 further comprising a control data transmitter for transmitting dynamic range control data to a source of the image signal.

19. The image processing apparatus of claim 1 arranged to receive the image signal being an 8 or 10 bit image signal, and arranged to apply a luma mapping on the image signal, based on at least the first target display reference, to obtain a high dynamic range output signal.

2. (canceled)

12. (canceled)

20. An image signal encoding apparatus comprising:

a receiver for receiving an encoded image;

a generator for generating an image signal comprising the encoded image and a target display reference indicative of a dynamic range of a target display for which the encoded image is encoded, wherein the target display reference comprises a white point luminance of the target display; and

a transmitter for transmitting the image signal.

22. The image signal encoding apparatus of claim 20 wherein the target display reference comprises an Electro Optical Transfer Function indication for the target display.

23. The image signal encoding apparatus of claim 20 wherein the target display reference comprises a tone mapping indication representing a tone mapping used to generate the first encoded image for the first target display.

25. An image signal encoding apparatus as claimed in claim 20 comprising an image encoding unit 550, arranged to encode an HDR image (IM_HDR) into the encoded image (Im_1) having its lumas encoded with 8 or 10 bits per pixel and intended for a display peak brightness greater than 400 nit, by means of a mapping function or algorithm which is characterized in that both an LDR rendering of this 8 or 10 bit luma per pixel image (Im_1) on an LDR display, and a HDR rendering of a HDR image recoverable from the 8 or 1.0 bit luma per pixel image (Im_1) when rendered on an HDR display, will be of sufficient quality according to a predetermined quality criterion, characterized in that data for uniquely characterizing the mapping function or algorithm is co-encoded in the first target display reference.

21. (canceled)

24. The image signal encoding apparatus of 20 wherein the generator is further arranged to generate the image signal to comprise a data field including dynamic range transform control data;

the dynamic range transform control data being indicative of a parameter of a dynamic range transform for the encoded image.

26. An image processing method comprising:

receiving an image signal, the image signal comprising at least a first encoded image and a first target display reference, the first target display reference being indicative of a dynamic range of a first target display for which the first encoded image is encoded, the first target display reference comprising at least a white point luminance of the first target display, and the receiving being able to handle white point luminances of at least 1000 nits and the first encoded image corresponding therewith;

generating an output image by applying a dynamic range transform to the first encoded image taking into account the first target display reference; and

outputting an output image signal comprising the output image.

28. A computer program product comprising computer program code means adapted to perform all the steps of claim 26 when said program is run on a computer.

27. A method of transmitting an image signal, the method comprising:

receiving an encoded image;

generating an image signal comprising the encoded image and a target display reference indicative of a dynamic range of a target display for which the encoded image is encoded, wherein the target display reference comprises a white point luminance of the target display; and

transmitting the image signal.

29. A storage medium having an image signal comprising at least a first encoded image comprising pixels which should be rendered with a luminance of at least 1000 nits and a first target display reference for the encoded image co-encoded in the image signal, the first target display reference being indicative of a dynamic range of a first target display for which the first encoded image is encoded, and the target display reference comprising a white point luminance of the target display.

30. (canceled)