Image processing apparatus and method of processing image

1. A method of processing an input image, the method comprising:

obtaining a first blurred image and a second blurred image having different blurring degrees, from the input image;

estimating illuminance of an image generated by combining the first blurred image and the second blurred image;

generating a dark region amplified image from the input image by amplifying pixel values of a dark region in the input image;

generating a bright region conserved image from the input image by maintaining pixel values of a bright region in the input image;

applying weights to the dark region amplified image and the bright region conserved image, respectively, according to the estimated illuminance;

combining the weighted dark region amplified image and the weighted bright region conserved image to generate a final image in which occurrence of a halo artifact effect is reduced; and

outputting the final image for display.

2. The method of claim 1 , wherein the input image is an image which is filtered to uniformly distribute information of the input image over an entire region of a histogram of the input image.

3. The method of claim 2 , wherein the filtering comprises:

generating a first curve and a second curve having different amplification degrees;

applying different weights to the first curve and the second curve, respectively, according to a ratio between a first maximum value and a second maximum value, wherein the first maximum value and the second maximum value are obtained by passing the input image through the first curve and the second curve, respectively;

generating a third curve by summing the weighted first curve and the weighted second curve; and

passing the input image through the generated third curve.

4. The method of claim 1 , wherein the estimating the illuminance comprises:

down-sampling the input image;

generating the first blurred image by interpolating the down-sampled input image;

generating the second blurred image formed of maximum value pixels respectively included in predetermined-size blocks of the input image;

applying different weights to the first blurred image and the second blurred image, respectively, according to characteristics of pixel values of the input image;

combining the weighted first blurred image and the weighted second blurred image; and

calculating the estimated illuminance from the combined image.

5. The method of claim 4 , further comprising processing an entire brightness of the combined image to be uniform and generate the estimated illuminance therefrom.

6. The method of claim 1 , wherein the generating the dark region amplified image comprises:

amplifying brightness of a dark region of the input image, and increasing contrast of the dark region of the input image; and

increasing contrast of a local region in the dark region the contrast of which is increased.

7. The method of claim 1 , wherein the generating the bright region conserved image comprises:

maintaining brightness of the bright region having greater brightness than a medium-brightness region of the input image; and

increasing contrast of the medium-brightness region of the input image.

8. The method of claim 1 , wherein the weights applied to the dark region amplified image and the bright region conserved image are different from each other according to whether the estimated illuminance is lower than a critical value.

9. The method of claim 8 , wherein the weight applied to the dark region amplified image is greater than the weight applied to the bright region conserved image if the estimated luminance is lower than the critical value.

10. The method of claim 1 , further comprising increasing contrast of the final image by performing brightness amplification of a dark region of the final image.

11. An image processing apparatus comprising:

a memory comprising computer executable instructions;

a processor configured to execute the computer executable instructions to implement:

an illuminance estimation unit configured to obtain a first blurred image and a second blurred image having different blurring degrees from an input image, and estimate illuminance of an image generated by combining the first blurred image and the second blurred image according to characteristics of the input image;

a dark region amplifying unit configured to generate a dark region amplified image from the input image by amplifying pixel values of a dark region in the input image;

a bright region conservation unit configured to generate a bright region conserved image from the input image by maintaining pixel values of a bright region in the input image; and

a combination unit configured to apply weights to the dark region amplified image and the bright region conserved image, respectively, according to the estimated illuminance, and combine the weighted dark region amplified image and the weighted bright region conserved image to generate a final image for display in which occurrence of a halo artifact effect is reduced to output for display.

12. The image processing apparatus of claim 11 , wherein the processor is further configured to execute the computer executable instructions to implement a filtering unit configured to generate the input image by uniformly distributing information of the input image over an entire region of a histogram of the input image.

13. The image processing apparatus of claim 11 , wherein the illuminance estimation unit comprises:

a first blurring unit configured to down-sample the input image and generate the first blurred image by interpolating the down-sampled input image;

a second blurring unit configured to generate the second blurred image formed maximum value pixels respectively included in predetermined-size blocks of the input image; and

an illuminance computation unit configured to apply different weights to the first blurred image and the second blurred image, respectively, according to characteristics of pixel values of the input image, combine the weighted first blurred image and the weighted second blurred image, and calculate the estimated illuminance from the combined image.

14. The image processing apparatus of claim 13 , wherein the processor is further configured to execute the computer executable instructions to implement a halo artifact reducing unit configured to process an entire brightness of the combined image to be uniform and generate the estimated illuminance therefrom.

15. The image processing apparatus of claim 11 , wherein the dark region amplifying unit comprises:

a global contrast increasing unit configured to amplify brightness of a dark region of the input image, and increase contrast of the dark region of the input image; and

a local contrast increasing unit configured to increase contrast of a local region in the dark region the contrast of which is increased.

16. The image processing apparatus of claim 11 , wherein the bright region conservation unit is configured to maintain brightness of the bright region having greater brightness than a medium-brightness region of the input image, and increase contrast of the medium-brightness region of the input image.

17. The image processing apparatus of claim 11 , wherein the weights applied to the dark region amplified image and the bright region conserved image are different from each other according to whether the estimated illuminance is lower than a critical value.

18. The image processing apparatus of claim 17 , wherein the weight applied to the dark region amplified image is greater than the weight applied to the bright region conserved image if the estimated luminance is lower than the critical value.

19. The image processing apparatus of claim 11 , wherein the combination unit is further configured to increase contrast of the final image by performing brightness amplification of a dark region of the final image.

20. A non-transitory computer readable medium storing a computer program for executing the method of claim 1 .