Image processing apparatus, image capturing apparatus, image processing method, and storage medium

Patent metadata

Field	Value
Publication number	US-2020327649-A1
Application number	US-202016845516-A
Country	US
Kind code	A1
Filing date	Apr 10, 2020
Priority date	Apr 15, 2019
Publication date	Oct 15, 2020
Grant date	—

Abstract

There is provided an image processing apparatus. An obtaining unit obtains image data having a first dynamic range, the image data having been applied with a predetermined tone curve, the predetermined tone curve being a tone curve representing visual characteristics based on a relationship between the first dynamic range and an absolute luminance that is output. A first compression unit compresses the image data from the first dynamic range to a second dynamic range narrower than the first dynamic range while maintaining the predetermined tone curve.

First claim

What is claimed is:

1 . An image processing apparatus comprising:
an obtaining unit configured to obtain image data having a first dynamic range, the image data having been applied with a predetermined tone curve, the predetermined tone curve being a tone curve representing visual characteristics based on a relationship between the first dynamic range and an absolute luminance that is output; and a first compression unit configured to compress the image data from the first dynamic range to a second dynamic range narrower than the first dynamic range while maintaining the predetermined tone curve.

2 . The image processing apparatus according to claim 1 , wherein
the predetermined tone curve is a tone curve conforming to OETF characteristics of PQ.

3 . The image processing apparatus according to claim 1 , wherein
the first compression unit multiplies the image data by a “second value/first value” to compress the image data from the first dynamic range to the second dynamic range, the first value is an output value of the predetermined tone curve in a case where a maximum value of the first dynamic range is an input, and the second value is an output value of the predetermined tone curve in a case where a maximum value of the second dynamic range is an input.

4 . The image processing apparatus according to claim 1 , further comprising:
a second compression unit configured to compress the image data from the first dynamic range to the second dynamic range by compressing luminance at a constant ratio in a linear region; a conversion unit configured to convert, by local tone mapping processing, tone characteristics of the image data compressed to the second dynamic range by the second compression unit; and a selection unit configured to select which of the first compression unit and the second compression unit is used to compress the image data from the first dynamic range to the second dynamic range.

5 . The image processing apparatus according to claim 1 , wherein
the first dynamic range is an HDR image dynamic range, and the second dynamic range is an SDR image dynamic range.

6 . The image processing apparatus according to claim 1 , wherein
the first compression unit determines the second dynamic range based on a luminance distribution of the image data, and the image processing apparatus further comprises a third compression unit configured to compress the image data, which have been compressed to the second dynamic range, to a third dynamic range narrower than the second dynamic range, by compressing luminance at a constant ratio in a linear region.

7 . The image processing apparatus according to claim 6 , wherein
the first compression unit determines the second dynamic range such that a width of the second dynamic range increases as the luminance distribution of the image data biases toward high luminance.

8 . The image processing apparatus according to claim 6 , wherein
the first dynamic range is an HDR image dynamic range, and the third dynamic range is an SDR image dynamic range.

9 . An image capturing apparatus comprising:
the image processing apparatus according to claim 1 ; an image capturing unit; and a generating unit configured to generate the image data based on an electrical signal generated by the image capturing unit.

10 . An image processing method executed by an image processing apparatus, comprising:
obtaining image data having a first dynamic range, the image data having been applied with a predetermined tone curve, the predetermined tone curve being a tone curve representing visual characteristics based on a relationship between the first dynamic range and an absolute luminance that is output; and compressing the image data from the first dynamic range to a second dynamic range narrower than the first dynamic range w aintaining the predetermined tone curve.

11 . A non-transitory computer-readable storage medium which stores a program for causing a computer to execute an image processing method comprising:
obtaining image data having a first dynamic range, the image data having been applied with a predetermined tone curve, the predetermined tone curve being a tone curve representing visual characteristics based on a relationship between the first dynamic range and an absolute luminance that is output; and compressing the image data from the first dynamic range to a second dynamic range narrower than the first dynamic range while maintaining the predetermined tone curve.

Assignees

• Canon Kk

Inventors

• Kimura Naoto

Classifications

• H04N23/741

  by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors · CPC title

• H04N23/80

  Camera processing pipelines; Components thereof · CPC title

• G06T2207/20208

  High dynamic range [HDR] image processing · CPC title

• G06T5/20

  using local operators · CPC title

• G06T5/50

  using two or more images, e.g. averaging or subtraction · CPC title