Electronic device and control method thereof

1. An electronic device comprising:

a storage configured to store first human visual system (HVS) recognition information according to a difference in luminance between adjacent pixels based on first maximum output luminance and second HVS recognition information according to a difference in luminance between adjacent pixels based on second maximum output luminance; and

a processor configured to,

obtain a first histogram regarding a difference in gradation between adjacent pixels of an input image based on the first maximum output luminance,

obtain a second histogram regarding a difference in gradation between adjacent pixels of the input image based on the second maximum output luminance,

obtain a third histogram regarding a difference in luminance between adjacent pixels of the input image based on the first HVS recognition information,

obtain a fourth histogram regarding a difference in luminance between adjacent pixels of the input image based on the second HVS recognition information, and

obtain a luminance value regarding the input image corresponding to the second maximum output luminance based on a difference between a first value obtained based on the first and third histogram information and a second value obtained based on the second and fourth histograms.

2. The device according to claim 1 , wherein the processor is configured to:

obtain a guide image by applying a guide tone mapping curve according to the second maximum output luminance to the input image,

obtain a fifth histogram regarding a difference in gradation between adjacent pixels of the guide image, and

obtain a luminance value regarding the input image corresponding to the second maximum output luminance based on the difference between the first value and the second value and a difference between the second and fifth histograms.

3. The device according to claim 2 , wherein the processor is configured to obtain a luminance value regarding the input image by applying a weight inversely proportional to a gradation value of each pixel of the input image to the difference between the second and fifth histograms.

4. The device according to claim 2 , wherein the processor is configured to obtain a sixth histogram by applying a weight matrix to the second histogram, and obtain a luminance value regarding the input image corresponding to the second maximum output luminance based on the difference between the first value and the second value, the difference between the second and fifth histograms, and the sixth histogram, and

wherein the weigh matrix is a diagonal matrix for applying 1 to elements in a diagonal direction.

5. The device according to claim 1 , wherein the processor is configured to:

obtain a plurality of second histograms regarding a difference in gradation between adjacent pixels of the input image based on the second maximum output luminance;

obtain a plurality of fourth histograms corresponding to the plurality of second histograms based on the second HVS recognition information;

obtain a plurality of second values based on a product between a plurality of elements included in each of the plurality of second histograms and a plurality of elements included in the corresponding fourth histogram; and

select one of the plurality of second histograms based on a difference value between each of the plurality of second values and the first value, and obtain a luminance value regarding the input image based on a fourth histogram corresponding to the selected second histogram.

6. The device according to claim 5 , wherein the processor is configured to:

obtain a plurality of images by applying a plurality of tone mapping curves to the input image, and obtain the plurality of second histograms based on a difference in gradation between adjacent pixels included in the plurality of images; and

identify a tone mapping curve corresponding to the selected second histogram among the plurality of tone mapping curves and obtain a luminance value regarding the input image by applying the identified tone mapping curve to the input image.

7. The device according to claim 1 , wherein the storage is configured to store mapping information regarding a gradation value of an image and a corresponding luminance value, and

wherein the processor is configured to obtain a luminance value corresponding to a gradation value of each of a plurality of pixels included in the input image based on the mapping information, and obtain the third and fourth histograms based on the obtained luminance value.

8. The device according to claim 1 , wherein the processor is configured to:

obtain a plurality of scaled images by scaling the input image to different sizes;

obtain a plurality of histograms regarding a difference in gradation between adjacent pixels of the plurality of scaled images based on the first maximum output luminance; and

obtain the first histogram by applying different weights to the plurality of histograms and adding up the plurality of histograms to which the weights are applied.

9. A method for controlling an electronic device storing first human visual system (HVS) recognition information according to a difference in luminance between adjacent pixels based on first maximum output luminance and second HVS recognition information according to a difference in luminance between adjacent pixels based on second maximum output luminance, the method comprising:

obtaining a first histogram regarding a difference in gradation between adjacent pixels of an input image based on the first maximum output luminance;

obtaining a second histogram regarding a difference in gradation between adjacent pixels of the input image based on the second maximum output luminance;

obtaining a third histogram regarding a difference in luminance between adjacent pixels of the input image based on the first HVS recognition information;

obtaining a fourth histogram regarding a difference in luminance between adjacent pixels of the input image based on the second HVS recognition information; and

obtaining a luminance value regarding the input image corresponding to the second maximum output luminance based on a difference between a first value obtained based on the first and third histogram information and a second value obtained based on the second and fourth histograms.

10. The method according to claim 9 , further comprising:

obtaining a guide image by applying a guide tone mapping curve according to the second maximum output luminance to the input image; and

obtaining a fifth histogram regarding a difference in gradation between adjacent pixels of the guide image,

wherein the obtaining the luminance value regarding the input image comprises obtaining a luminance value regarding the input image corresponding to the second maximum output luminance based on the difference between the first value and the second value and a difference between the second and fifth histograms.

11. The method according to claim 10 , wherein the obtaining the luminance value regarding the input image comprises obtaining a luminance value regarding the input image by applying a weight inversely proportional to a gradation value of each pixel of the input image to the difference between the second and fifth histograms.

12. The method according to claim 9 , wherein the obtaining the second histogram comprises obtaining a plurality of second histograms regarding a difference in gradation between adjacent pixels of the input image based on the second maximum output luminance, and

wherein the obtaining the luminance value regarding the input image comprises:

obtaining a plurality of second values based on a product between a plurality of elements included in each of the plurality of second histograms and a plurality of elements included in the corresponding fourth histogram;

selecting one of the plurality of second histograms based on a difference value between each of the plurality of second values and the first value; and

obtaining a luminance value regarding the input image based on a fourth histogram corresponding to the selected second histogram.

13. The method according to claim 12 , wherein the obtaining the second histogram comprises:

obtaining a plurality of images by applying a plurality of tone mapping curves to the input image; and

obtaining the plurality of second histograms based on a difference in gradation between adjacent pixels included in the plurality of images; and

wherein the obtaining the luminance value regarding the input image comprises:

identifying a tone mapping curve corresponding to the selected second histogram among the plurality of tone mapping curves; and

obtaining a luminance value regarding the input image by applying the identified tone mapping curve to the input image.

14. The method according to claim 9 , wherein the obtaining the third histogram comprises:

obtaining a luminance value corresponding to a gradation value of each of a plurality of pixels included in the input image based on mapping information regarding a gradation value of an image stored in the electronic device and a corresponding luminance value; and

obtaining the third histogram based on the first HVS recognition information and the obtained luminance value, and

wherein the obtaining the fourth histogram comprises:

obtaining a luminance value corresponding to a gradation value of each of the plurality of pixels included in the input image based on the mapping information; and

obtaining the fourth histogram based on the second HVS recognition information and the obtained luminance value.