Image processing device and image enhancing method thereof

1. An image processing device comprising a processor configured to implement:

a first corrector configured to generate a first corrected image obtained by correcting a local intensity of an input image; and

a second corrector configured to generate a second corrected image obtained by correcting a global intensity of the first corrected image based on a histogram of the input image,

wherein the first corrector comprises:

a local intensity calculator configured to calculate a representative local intensity value of a current pixel by calculating a weighted sum of a first representative local intensity value and a second representative local intensity value with a weight value;

a gamma calculator configured to calculate a local gamma value for correcting a pixel value of the current pixel by using the representative local intensity value of the current pixel; and

a local intensity corrector configured to correct the pixel value of the current pixel by applying the local gamma value to the pixel value of the current pixel,

wherein the local intensity calculator is configured to

calculate the weight value of the current pixel based on an intensity distribution of a peripheral area of the current pixel and a global intensity distribution of the input image,

calculate the first representative local intensity value by calculating a first average value of the pixel value of the current pixel and pixel values of peripheral pixels in a first window having a first size, and

calculate the second representative local intensity value by calculating a second average value of the pixel value of the current pixel and the pixel values of peripheral pixels in a second window having a second size that is smaller than the first size.

2. The image processing device of claim 1 , wherein the local intensity calculator is configured to move the second window in a plurality of directions with respect to the current pixel, and calculate the second average value of the pixel value of the current pixel and the pixel values of peripheral pixels in the second window in the plurality of directions.

3. The image processing device of claim 2 , wherein the local intensity calculator is configured to calculate, as the second representative local intensity value, a minimum average value calculated in a direction corresponding to a minimum value from among a plurality of absolute values of a plurality of differences between a plurality of average values calculated in the plurality of directions and the pixel value of the current pixel.

4. The image processing device of claim 2 , wherein a position of the current pixel in the second window is modified according to the plurality of directions.

5. The image processing device of claim 1 , wherein the gamma calculator is configured to calculate the local gamma value by using the representative local intensity value of the current pixel as a gamma weight value and calculating a weighted sum of a first gamma value set to correct a first portion that is brighter than a reference intensity and a second gamma value set to correct a second portion that is darker than the reference intensity.

6. The image processing device of claim 1 , wherein the second corrector is configured to correct the pixel value of the current pixel of the first corrected image based on a result of comparing the pixel value of the current pixel of the first corrected image with a plurality of average intensity values corresponding to a plurality of cumulative probabilities preset in the histogram.

7. An image enhancing method performed by an image processing device, the image enhancing method comprising:

calculating a weight value of a current pixel based on an intensity distribution of a peripheral area of the current pixel and a global intensity distribution of an input image;

obtaining a first representative local intensity value by calculating a first average value of a pixel value of the current pixel and pixel values of peripheral pixels in a first window having a first size;

obtaining a second representative local intensity value by calculating a second average value of the pixel value of the current pixel and the pixel values of peripheral pixels in a second window having a second size that is smaller than the first size;

calculating a representative local intensity value of the current pixel by calculating a weighted sum of the first representative local intensity value and the second representative local intensity value with the weight value;

calculating a local gamma value for correcting the pixel value of the current pixel by using the representative local intensity value of the current pixel;

generating a first corrected image by correcting the pixel value of the current pixel by applying the local gamma value to the pixel value of the current pixel; and

generating a second corrected image obtained by correcting a global intensity of the first corrected image based on a histogram of the input image.

8. The image enhancing method of claim 7 , wherein the calculating the second average value comprising moving the second window in a plurality of directions with respect to the current pixel, and calculating the second average value of the pixel value of the current pixel and the pixel values of peripheral pixels in the second window in the plurality of directions.

9. The image enhancing method of claim 8 , wherein the calculating the second average value comprising calculating a minimum average value calculated in a direction corresponding to a minimum value from among a plurality of absolute values of a plurality of differences between a plurality of average values calculated in the plurality of directions and the pixel value of the current pixel.

10. The image enhancing method of claim 8 , wherein a position of the current pixel in the second window is modified according to the plurality of directions.

11. The image enhancing method of claim 7 , wherein the calculating the local gamma value comprising calculating the local gamma value by using the representative local intensity value of the current pixel as a gamma weight value and calculating a weighted sum of a first gamma value set to correct a first portion that is brighter than a reference intensity and a second gamma value set to correct a second portion that is darker than the reference intensity.

12. The image enhancing method of claim 7 , wherein the generating the second corrected image comprising correcting the pixel value of the current pixel of the first corrected image based on a result of comparing the pixel value of the current pixel of the first corrected image with a plurality of average intensity values corresponding to a plurality of cumulative probabilities preset in the histogram, with the pixel value of the current pixel of the first corrected image.