Image processing apparatus, display apparatus, and computer-readable storage medium

Patent metadata

Field	Value
Publication number	US-10290254-B2
Application number	US-201715856079-A
Country	US
Kind code	B2
Filing date	Dec 28, 2017
Priority date	Jul 8, 2015
Publication date	May 14, 2019
Grant date	May 14, 2019

Abstract

Technology is known for correcting the gradation characteristics of an input image signal in accordance with the characteristics of a display device, but a correction that is suitable for the usage of the display device is desired. Provided is an image processing apparatus including a first gradation converting section that converts a gradation of an image signal input thereto; a sharpening process section that performs a sharpening process on the image signal after the gradation has been converted by the first gradation converting section; a second gradation converting section that converts the gradation of the image signal after the sharpening process has been performed; and a display control section that displays an image indicated by the image signal after the gradation has been converted by the second gradation converting section, in a display device.

First claim

What is claimed is:

1. An image processing apparatus comprising a processor that is configured to perform processes including:
a first gradation converting process that converts a gradation of an image signal input thereto;
a sharpening process performed on the image signal after the gradation has been converted by the first gradation converting process;
a second gradation converting process that converts the gradation of the image signal after the sharpening process has been performed; and
a display control process that displays an image indicated by the image signal after the gradation has been converted by the second gradation converting process, in a display device, wherein
the second gradation converting process converts the gradation of the image signal after the sharpening process has been performed, to perform a γ correction that cancels out a γ characteristic of the display device,
a filter coefficient of a sharpening filter applied to the image signal by the sharpening process is linear with respect to an output signal of the display device,
the sharpening process includes:
a luminance calculating process that calculates a luminance of each of a plurality of pixels of the image indicated by the image signal;
a difference calculating process that calculates a difference between the luminance and a luminance resulting from the sharpening filter being applied to the luminance, for each of the plurality of pixels; and
a luminance changing process that changes the luminance of each of the plurality of pixels, based on the difference calculated by the difference calculating process, and

the luminance changing process, for each of the plurality of pixels, obtains a first difference value between a maximum value and an upper limit value of RGB values of the pixel and a second difference value between a minimum value and a lower limit value of the RGB values of the pixel and, when an absolute value of the difference calculated by the difference calculating process is larger than a minimum difference value among the first difference value and the second difference value, changes the luminance of the pixel based on the minimum difference value.

2. The image processing apparatus according to claim 1 , wherein
the sharpening process performed on the image signal removes a scattered component from the image indicated by the image signal and performs at least one of amplifying an attenuated component and adding the attenuated component.

3. The image processing apparatus according to claim 1 , wherein
the difference calculating process, for each of the plurality of pixels, calculates a difference between (i) a luminance resulting from applying to the luminance the sharpening filter generated based on a filter characteristic calculated by performing an inverse Fourier transform on an inverse function of a Modulation Transfer Function (MTF) of the display device displaying the image indicated by the image signal and (ii) the luminance calculated by the luminance calculating process.

4. The image processing apparatus according to claim 1 , wherein
the sharpening process further includes:
a color identifying process that identifies a pixel with a saturation that is higher than a predetermined threshold value, among the plurality of pixels of the image indicated by the image signal; and
a mask generating process that generates a mask for pixels identified by the color identifying process as having a saturation that is higher than the predetermined threshold value that are present in a range of the sharpening filter, and

the luminance changing process does not change the luminance of the pixels for which the mask is generated.

5. A display apparatus comprising:
the image processing apparatus according to claim 1 ; and
the display device.

6. The display apparatus according to claim 5 , wherein
a Modulation Transfer Function (MTF) of the display apparatus in a case where the sharpening process is performed is closer to 1.0 than the MTF of the display apparatus in a case where the sharpening process is not performed.

7. A non-transitory computer-readable storage medium storing thereon a program that causes a computer to function as:
a first gradation converting section that converts a gradation of an image signal input thereto;
a sharpening process section that performs a sharpening process on the image signal after the gradation has been converted by the first gradation converting section;
a second gradation converting section that converts the gradation of the image signal after the sharpening process has been performed; and
a display control section that displays an image indicated by the image signal after the gradation has been converted by the second gradation converting section, in a display device, wherein
the second gradation converting section converts the gradation of the image signal after the sharpening process has been performed, to perform a γ correction that cancels out a γ characteristic of the display device,
a filter coefficient of a sharpening filter applied to the image signal by the sharpening process section is linear with respect to an output signal of the display device,
the sharpening process section includes:
a luminance calculating section that calculates a luminance of each of a plurality of pixels of the image indicated by the image signal;
a difference calculating section that calculates a difference between the luminance and a luminance resulting from the sharpening filter being applied to the luminance, for each of the plurality of pixels; and
a luminance changing section that changes the luminance of each of the plurality of pixels, based on the difference calculated by the difference calculating section, and

the luminance changing section, for each of the plurality of pixels, obtains a first difference value between a maximum value and an upper limit value of RGB values of the pixel and a second difference value between a minimum value and a lower limit value of the RGB values of the pixel and, when an absolute value of the difference calculated by the difference calculating section is larger than a minimum difference value among the first difference value and the second difference value, changes the luminance of the pixel based on the minimum difference value.

8. An image processing method comprising:
a first gradation converting process that converts a gradation of an image signal input thereto;
a sharpening process performed on the image signal after the gradation has been converted by the first gradation converting process;
a second gradation converting process that converts the gradation of the image signal after the sharpening process has been performed; and
a display control process that displays an image indicated by the image signal after the gradation has been converted by the second gradation converting process, in a display device, wherein
the second gradation converting process converts the gradation of the image signal after the sharpening process has been performed, to perform a γ correction that cancels out a γ characteristic of the display device,
a filter coefficient of a sharpening filter applied to the image signal by the sharpening process is linear with respect to an output signal of the display device,
the sharpening process includes:
a luminance calculating process that calculates a luminance of each of a plurality of pixels of the image indicated by the image signal;
a difference calculating process that calculates a difference between the luminance and a luminance resulting from the sharpening filter being applied to the luminance, for each of the plurality of pixels; and
a luminance changing process that changes the luminance of each of the plurality of pixe

Assignees

• Eizo Corp

Inventors

• Ogaki Mamoru
• Bamba Yusuke
• Aoki Reo

Classifications

• G09G2360/16

  Calculation or use of calculated indices related to luminance levels in display data · CPC title

• G09G5/10 Primary

  Intensity circuits · CPC title

• G09G5/06

  using colour palettes, e.g. look-up tables · CPC title

• G06T5/00

  Image enhancement or restoration · CPC title

• G09G2320/0276

  for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction · CPC title