Image processing apparatus, imaging apparatus, and image processing method

Patent metadata

Field	Value
Publication number	US-2016196640-A1
Application number	US-201514971446-A
Country	US
Kind code	A1
Filing date	Dec 16, 2015
Priority date	Jan 6, 2015
Publication date	Jul 7, 2016
Grant date	—

Abstract

An image processing apparatus according to the present invention comprises a histogram generating section for generating a histogram by counting a frequency value for each gradation of a predetermined number of gradations as brightness distribution of input image data, a distribution processing section for distributing a count value of the histogram to adjacent gradations, a cumulative histogram generating section for generating a cumulative histogram by accumulating the histograms obtained by the histogram generating section from a low gradation side, and a gradation correction processing section for performing contrast correction by using the cumulative histogram, wherein the distribution processing section fixes a distribution amount to the predetermined number of gradations when distributing the count value to the adjacent gradations.

First claim

What is claimed is:

1 . An image processing apparatus comprising:
a histogram generating section for generating a histogram by counting a frequency value for each gradation of a predetermined number of gradations as brightness distribution of input image data; a distribution processing section for distributing a count value of the histogram to adjacent gradations; a cumulative histogram generating section for generating a cumulative histogram by accumulating the histograms obtained by the histogram generating section from a low gradation side; and a gradation correction processing section for performing contrast correction by using the cumulative histogram, wherein the distribution processing section fixes a distribution amount to the predetermined number of gradations when distributing the count value to the adjacent gradations.

2 . An imaging apparatus comprising:
an imaging section for imaging a field and outputting image data; a histogram generating section for generating a histogram by counting a frequency value for each gradation of a predetermined number of gradations as brightness distribution of the input image data; a distribution processing section for distributing a count value of the histogram to adjacent gradations; a cumulative histogram generating section for generating a cumulative histogram by accumulating the histograms obtained by the histogram generating section from a low gradation side; and a gradation correction processing section for performing contrast correction by using the cumulative histogram, wherein the distribution processing section fixes a distribution amount to the predetermined number of gradations when distributing the count value to the adjacent gradations.

3 . The imaging apparatus according to claim 2 , wherein
if an imaging operation of the imaging section is photographing of a still image, the distribution processing section makes the gradation number for which the distribution amount is fixed equal to or smaller than the case of photographing of a moving image.

4 . The imaging apparatus according to claim 2 , further comprising:
a detecting section for obtaining an area in an image; and an area determining section for determining whether a local area of the image data is in the area detected by the detecting section, wherein the histogram generating section generates a histogram for each local region of the image data; and the distribution processing section, if it is determined by the area determining section that the local area is in the area, changes the gradation number for which the distribution amount is fixed.

5 . The imaging apparatus according to claim 2 , wherein
the distribution processing section distributes the fixed distribution amount so as to be “W 1 =1/(stabN+1)” by using the target gradation number.

6 . The imaging apparatus according to claim 5 , wherein
in the distribution processing section, a maximum amount of the distribution amount varied in accordance with a pixel value is as follows by using the fixed distribution amount and the gradation number for fixed distribution:
W 23=1−( W 1×stab N )

where W 23 : distribution weighting coefficient W 1 : distribution weighting coefficient stabN: gradation number.

7 . The imaging apparatus according to claim 2 , wherein
in the distribution processing section, the distribution amount varied in accordance with a pixel value is distributed to a gradation adjacent to the gradation for which the distribution amount is fixed.

8 . The imaging apparatus according to claim 7 , wherein
in the distribution processing section, a maximum amount of the distribution amount varied in accordance with a pixel value is as follows by using the fixed distribution amount and the gradation number for fixed distribution:
W 23=1−( W 1×stab N )

where W 23 : distribution weighting coefficient W 1 : distribution weighting coefficient stabN: gradation number.

9 . An image processing method comprising:
a histogram generating step of generating a histogram by counting a frequency value for each gradation of a predetermined number of gradations as brightness distribution of input image data; a distribution processing step of distributing a count value of the histogram to adjacent gradations; a cumulative histogram generating step of generating a cumulative histogram by accumulating the histograms obtained by the histogram generating step from a low gradation side; and a gradation correction processing step of performing contrast correction by using the cumulative histogram, wherein the distribution processing step fixes a distribution amount to the predetermined number of gradations when distributing the count value to the adjacent gradations.

10 . A non-transitory computer-readable medium storing a computer program for an image processing apparatus, the computer program comprising:
a histogram generating step of generating a histogram by counting a frequency value for each gradation of a predetermined number of gradations as brightness distribution of input image data; a distribution processing step of distributing a count value of the histogram to adjacent gradations; a cumulative histogram generating step of generating a cumulative histogram by accumulating the histograms obtained by the histogram generating step from a low gradation side; and a gradation correction processing step of performing contrast correction by using the cumulative histogram, wherein the distribution processing step fixes a distribution amount to the predetermined number of gradations when distributing the count value to the adjacent gradations.

Assignees

• Olympus Corp

Inventors

• Kino Tatsuya

Classifications

• G06T5/40 Primary

  using histogram techniques · CPC title

• G06T2207/20208

  High dynamic range [HDR] image processing · CPC title

• H04N23/88

  for colour balance, e.g. white-balance circuits or colour temperature control · CPC title

• H04N1/4074

  using histograms · CPC title

• H04N1/6027

  Correction or control of colour gradation or colour contrast (H04N1/6058 takes precedence) · CPC title