Methods, apparatus, and systems for extended high dynamic range (“HDR”) HDR to HDR tone mapping

Patent metadata

Field	Value
Publication number	US-10148906-B2
Application number	US-201715460254-A
Country	US
Kind code	B2
Filing date	Mar 16, 2017
Priority date	Mar 16, 2016
Publication date	Dec 4, 2018
Grant date	Dec 4, 2018

Abstract

Aspects of present principles are directed to methods and apparatus for tone mapping a high dynamic range image. The apparatus includes a processor for performing the following and the method includes the following: obtaining a luminance component of the high dynamic range image; determining an HDR to HDR tone mapper curve; determining a tone compressed image by applying the HDR to HDR tone mapper curve to the luminance component of the high dynamic range image; wherein the HDR to HDR tone mapper curve comprises a first part for dark and mid-tone levels, and a second part for highlights.

First claim

The invention claimed is:

1. A method for tone mapping an input image having a first dynamic range with a peak input luminance I max into an output image having a second lower dynamic range with a lower peak output luminance I o max , the method comprising
obtaining a luminance component of the input image;
determining a tone mapper curve from the first dynamic range to the second dynamic range;
determining said output image by applying the tone mapper curve to the luminance component of the input image;
wherein the tone mapper curve comprises a first linear part for dark and mid-tone levels and a second non-linear part for highlights, and
wherein the first linear part has a slope s that is a monotonically non-increasing function of a measure of uniformity of distribution of the luminance component in a bright region of a luminance histogram of the luminance component of the input image such that said slope s will be lower than or equal to 1 but higher than or equal to a ratio s l of the peak output luminance I o max and the peak input luminance I max .

2. The method of claim 1 , wherein the bright region of the luminance histogram is defined as being delineated between a lower bound ζ l and an upper bound ζ u positioned in a luminance range of the input image, wherein the lower bound ζ l proportional to the ratio s l of the peak output luminance I o max and the peak input luminance I max .

3. The method of claim 1 , wherein a mid-to-high threshold τ defined as separating the first linear part and the second non-linear part of the tone mapper curve is smaller than the peak output luminance I o max .

4. The method of claim 3 , wherein the mid-to-high threshold r is large enough to cover more than (100−n) % of the pixels of a frame or image, wherein n is superior or equal to 2.

5. The method of claim 1 , wherein the measure of uniformity of distribution of the luminance component in the bright region is determined as a ratio between a mean μ and a standard deviation υ of a number of pixels of said input image over bins of the bright region of said luminance histogram.

6. The method of claim 1 , wherein a relationship between the slope s and the measure of uniformity is non-linear.

7. The method of claim 6 , wherein the slope s is determined as follows

s
=

{

1

≤

ϱ
1

(

-
3

⁢

2

+

2
⁢

3

+
1

)

⁢

(

1
-

s
l

)

+

s
l

1

<
<

ϱ
2

s
l

≥

ϱ
1

where

=

µ
υ

-

ϱ
1

2

-

ϱ
1

,

and
where parameters 1 , 2 define transition points of the tone mapper curve representing the slope s as function of parameter .

8. The method of claim 1 , further comprising signaling information representative of the tone mapper curve.

9. The method of claim 8 , wherein the signaling is performed using at least one syntax element included in at least one of a Picture Parameter Set (PPS), a Sequence Parameter Set (SPS), a Supplemental Enhancement Information (SEI) message, a Video Usability Information (VUI), Consumer Electronics Association (CEA) message, and a header.

10. An apparatus for tone mapping an input image having a first dynamic range with a peak input luminance I max into an output image having a second lower dynamic range with a lower peak output luminance I o max , the apparatus comprising at least one processor configured for:
obtaining a luminance component of the input image;
determining a tone mapper curve from the first dynamic range to the second dynamic range;
determining said output image by applying the tone mapper curve to the luminance component of the input image;
wherein the tone mapper curve comprises a first linear part for dark and mid-tone levels and a second non-linear part for highlights, and
wherein the first linear part has a slope s that is a monotonically non-increasing function of a measure of uniformity of distribution of the luminance component in a bright region of a luminance histogram of the luminance component of the input image such that said slope s will be lower than or equal to 1 but higher than or equal to a ratio s l of the peak output luminance I o max and the peak input luminance I max .

11. The apparatus of claim 10 , wherein the bright region of the luminance histogram is defined as being delineated between a lower

Assignees

• Thomson Licensing
• Interdigital Vc Holdings Inc

Inventors

• Seifi Mozhdeh
• Reinhard Erik
• Poirier Guillaume

Classifications

• H04N25/57

  Control of the dynamic range · CPC title

• H04N5/355

  Electricity · mapped topic

• G06T2207/20208

  High dynamic range [HDR] image processing · CPC title

• H04N7/01 Primary

  Conversion of standards {, e.g. involving analogue television standards or digital television standards processed at pixel level} · CPC title

• G06T5/009

  Physics · mapped topic