Display device and method for controlling brightness thereof

1. A display device comprising:

a storage configured to store output brightness information for each gradation according to brightness information of an image; and

a processor configured to:

acquire target brightness corresponding to brightness information of an input image on the basis of the information stored in the storage,

acquire a target light amount on the basis of a light amount of the input image,

acquire a plurality of correction effects corresponding to a plurality of correction images by applying a plurality of gradation adjustment curves to the input image,

acquire a gradation adjustment curve corresponding to the maximum correction effect among the plurality of correction effects, and

adjust and output a gradation for each pixel of the input image on the basis of the acquired gradation adjustment curve,

wherein the plurality of correction effects are acquired on the basis of a difference in a perceived visual sense between each of the plurality of correction images and the input image, a difference between the brightness of each of the plurality of correction images and the target brightness, and a difference between the light amount of each of the plurality of correction images and the target light amount.

2. The display device of claim 1 ,

wherein the target brightness is the maximum output brightness corresponding to the brightness information of the input image, and

the brightness of each of the plurality of correction images is the maximum output brightness corresponding to the brightness information of each of the plurality of correction images.

3. The display device of claim 1 ,

wherein the processor is configured to:

acquire the light amount of the input image by summing up the brightness of each of the plurality of pixels included in the input image, and

the target light amount is a light amount which is a reduced amount of the light amount of the input image by a predetermined ratio.

4. The display device of claim 1 ,

wherein the processor is configured to:

acquire a first correction image by applying a first gradation adjustment curve among the plurality of gradation adjustment curves to the input image,

calculate a difference in a first perceived visual sense on the basis of a difference value between a graph indicating the gradation for each pixel included in the input image and the first gradation adjustment curve,

calculate a first light amount difference between the light amount of the first correction image and the target light amount,

calculate a first brightness difference between the maximum output brightness of the first correction image and the target brightness, and

acquire a first correction effect on the basis of the following formula:

E=α SIM ω SIM +α LUMA ω LUMA +α GRARE ω GRARE ,

wherein α SIM is a first weighted value, α LUMA is a second weighted value, α GRARE is a third weighted value, ω SIM is the difference in the first perceived visual sense, ω LUMA is the first light amount difference, and ω GRARE is the first brightness difference, and each of the α SIM , the α LUMA , and the α GRARE is a weighted value that is neural network trained on the basis of a plurality of sample images.

5. The display device of claim 4 ,

wherein the processor is configured to:

acquire a second correction image by applying a second gradation adjustment curve among the plurality of gradation adjustment curves to the input image,

calculate a difference in a second perceived visual sense on the basis of the second gradation adjustment curve, and calculate a second light amount difference and a second brightness difference on the basis of the second correction image,

acquire a second correction effect on the basis of the difference in the second perceived visual sense, the second light amount difference, and the second brightness difference, and

adjust and output the gradation for each pixel of the input image on the basis of a gradation adjustment curve corresponding to the smaller value between the first correction effect and the second correction effect.

6. The display device of claim 1 ,

wherein the plurality of gradation adjustment curves is a graph indicated by the following formula, and have different αs and βs:

t

i

=

α

×

i

2

⁢

5

⁢

5

⁢

(

2.2

+

β

)

,

wherein i means the gradation for each pixel included in an input image, α and β respectively mean first and second adjustment values, and t i means the gradation of a correction image.

7. The display device of claim 1 , further comprising:

a display,

wherein the storage stores information for a current gain for each maximum brightness of an image, and

the processor is configured to:

based on the gradation for each pixel of the input image being adjusted on the basis of the acquired gradation adjustment curve, acquire current gain information corresponding to the maximum output brightness of the adjusted input image from the storage, and

control currents provided to the display on the basis of the current gain information.

8. The display device of claim 1 ,

wherein brightness information of the image is an average picture level (APL) of the image, and

output brightness information for each gradation according to the brightness information of the image is the maximum output brightness information for each gradation according to the average picture level calculated on the basis of the power consumption of the display device.

9. The display device of claim 1 ,

wherein the processor is configured to:

based on the gradation for each pixel of the input image being adjusted on the basis of the acquired gradation adjustment curve, identify the adjusted input image as a plurality of blocks, and acquire a local gradation adjustment curve corresponding to each of the plurality of blocks on the basis of gradation distribution and gradation average values of each of the plurality of blocks, and

adjust the gradation for each pixel of each of the plurality of blocks on the basis of the acquired local gradation adjustment curve.

10. The display device of claim 9 ,

wherein the processor is configured to:

apply the first weighted value to each gradation value of pixels included in a first block of an image to which the gradation adjustment curve was applied,

apply the second weighted value to each gradation value of pixels included in a block corresponding to the first block in an image to which the local gradation adjustment curve was applied, and

adjust and output the gradation for each pixel on the basis of the gradation value to which the first weighted value was applied and the gradation value to which the second weighted value was applied.

11. A method for controlling brightness of a display device storing output brightness information for each gradation according to brightness information of an image, the method comprising:

acquiring target brightness corresponding to brightness information of an input image on the basis of the stored information;

acquiring a target light amount on the basis of a light amount of the input image;

acquiring a plurality of correction effects corresponding to a plurality of correction images by applying a plurality of gradation adjustment curves to the input image;

acquiring a gradation adjustment curve corresponding to the maximum correction effect among the plurality of correction effects; and

adjusting and outputting a gradation for each pixel of the input image on the basis of the acquired gradation adjustment curve,

wherein the plurality of correction effects are acquired on the basis of a difference in a perceived visual sense between each of the plurality of correction images and the input image, a difference between the brightness of each of the plurality of correction images and the target brightness, and a difference between the light amount of each of the plurality of correction images and the target light amount.

12. The controlling method of claim 11 ,

wherein the target brightness is the maximum output brightness corresponding to the brightness information of the input image, and

the brightness of each of the plurality of correction images is the maximum output brightness corresponding to the brightness information of each of the plurality of correction images.

13. The controlling method of claim 11 ,

wherein the acquiring a target light amount comprises:

acquiring the light amount of the input image by summing up the brightness of each of the plurality of pixels included in the input image, and

the target light amount is a light amount which is a reduced amount of the light amount of the input image by a predetermined ratio.

14. The controlling method of claim 11 ,

wherein the acquiring a plurality of correction effects comprises:

acquiring a first correction image by applying a first gradation adjustment curve among the plurality of gradation adjustment curves to the input image;

calculating a difference in a first perceived visual sense on the basis of a difference value between a graph indicating the gradation for each pixel included in the input image and the first gradation adjustment curve;

calculating a first light amount difference between the light amount of the first correction image and the target light amount;

calculating a first brightness difference between the maximum output brightness of the first correction image and the target brightness; and

acquiring a first correction effect on the basis of the following formula:

E=α SIM ω SIM +α LUMA ω LUMA +α GRARE ω GRARE ,

wherein α SIM is a first weighted value, α LUMA is a second weighted value, α GRARE is a third weighted value, ω SIM is the difference in the first perceived visual sense, ω LUMA is the first light amount difference, and ω GRARE is the first brightness difference, and each of the α SIM , the α LUMA , and the α GRARE is a weighted value that is neural network trained on the basis of a plurality of sample images.

15. The controlling method of claim 14 ,

wherein the acquiring a plurality of correction effects comprises:

acquiring a second correction image by applying a second gradation adjustment curve among the plurality of gradation adjustment curves to the input image;

calculating a difference in a second perceived visual sense on the basis of the second gradation adjustment curve, and calculating a second light amount difference and a second brightness difference on the basis of the second correction image; and

acquiring a second correction effect on the basis of the difference in the second perceived visual sense, the second light amount difference, and the second brightness difference,

wherein the adjusting and outputting the gradation for each pixel of the input image comprises:

adjusting and outputting the gradation for each pixel of the input image on the basis of a gradation adjustment curve corresponding to the smaller value between the first correction effect and the second correction effect.