Defog system and defog method

1. A defog system comprising:

an illuminance sensor configured to detect ambient illuminance; and

at least one processor to implement:

a level determiner configured to determine a defog level of an input image based on the ambient illuminance; and

a defogger configured to determine whether to defog the input image based on skewness and kurtosis of a histogram of the input image, and, in response to the defogger determining to defog the input image, determine a fog condition of the input image based on a cumulative probability of the histogram, and defog the input image based on the defog level,

wherein the defogger comprises:

a histogram generator configured to generate the histogram of the input image:

an analyzer configured to determine the skewness and the kurtosis of the histogram;

a fog detector configured to, in response to the skewness and the kurtosis being within a range, detect a first minimum luminance, in which the cumulative probability of the histogram corresponds to a minimum reference probability, and a first maximum luminance, in which the cumulative probability of the histogram corresponds to a maximum reference probability and

a scaler configured to scale the input image by resetting the first minimum luminance and the first maximum luminance respectively to a second minimum luminance and a second maximum luminance based on the defog level, and

wherein the fog detector is further configured to, in response to at least one among the skewness and the kurtosis being outside the range, reduce the minimum reference probability, and detect the first minimum luminance, in which the cumulative probability of the histogram corresponds to the reduced minimum reference probability.

2. The defog system of claim 1 , wherein the second minimum luminance is less than the first minimum luminance, and

wherein the second maximum luminance is greater than the first maximum luminance.

3. The defog system of claim 1 , wherein the fog detector is further configured to reduce the minimum reference probability in proportion to a degree to which the at least one among the skewness and the kurtosis is outside the range.

4. The defog system of claim 1 , wherein the scaler is further configured to reduce, as the defog level decreases, an adjustment width between the first minimum luminance and the second minimum luminance and an adjustment width between the first maximum luminance and the second maximum luminance.

5. The defog system of claim 1 , wherein the level determiner is further configured to:

output a maximum defog level signal in response to an amplification value of the ambient illuminance being less than a first threshold;

output a minimum defog level signal in response to the amplification value being greater than a second threshold; and

output a respective defog level signal in response to the amplification value being between the first threshold and the second threshold.

6. The defog system of claim 5 , wherein the level determiner is further configured to change the respective defog level signal as the amplification value changes between the first threshold and the second threshold.

7. The defog system of claim 5 , wherein the level determiner is further configured to reduce the respective defog level signal as the amplification value changes from the first threshold to the second threshold.

8. The defog system of claim 1 , further comprising:

an edge detector configured to detect an edge amount of the input image; and

a gamma applier configured to, in response to the edge amount being less than or equal to a threshold, apply a gamma curve to the defogged input image based on a relationship between the edge amount and a preset luminance.

9. A defog method comprising:

detecting an ambient illuminance;

determining a defog level of an input image based on the ambient illuminance;

determining whether to defog the input image based on skewness and kurtosis of a histogram of the input image;

in response to the determining to defog the input image, determining a fog condition of the input image based on a cumulative probability of the histogram, and defogging the input image based on the defog level;

generating the histogram of the imput image; and

determining the skewness and the kurtosis of the histogram

wherein the determining the fog condition comprises, in response to the skewness and the kurtosis being within a range, detecting a first minimum luminance, in which the cumulative probability of the histogram corresponds to a minimum reference probability, and a first maximum luminance, in which the cumulative probability of the histogram corresponds to a maximum reference probability,

wherein the defogging the input image comprises scaling the input image by resetting the first maximum luminance and the first maximum luminance respectively to a second minimum luminance and a second maximum luminance based on the defog level, and

wherein the determining the fog condition further comprises, in response to at least one among the skewness and the kurtosis being outside the range, reducing the minimum reference probability, and detecting the first minimum luminance, in which the cumulative probability of the histogram corresponds to the reduced minimum reference probability.

10. The defog method of claim 9 , wherein the second minimum luminance is less than the first minimum luminance, and

the second maximum luminance is greater than the first maximum luminance.

11. The defog method of claim claim 9 , wherein the reducing the minimum reference probability comprises reducing the minimum reference probability in proportion to a degree to which the at least one among the skewness and the kurtosis is outside the range.

12. The defog method of claim 9 , wherein the scaling the input image comprises reducing, as the defog level decreases, an adjustment width between the first minimum luminance and the second minimum luminance and an adjustment width between the first maximum luminance and the second maximum luminance.

13. The defog method of claim 9 , wherein the determining the defog level comprises:

outputting a maximum defog level signal in response to an amplification value of the ambient illuminance being less than a first threshold;

outputting a minimum defog level signal in response to the amplification value being greater than a second threshold; and

outputting a respective defog level signal in response to the amplification value being between the first threshold and the second threshold.

14. The defog method of claim 13 , wherein the outputting the respective defog level signal comprises changing the respective defog level signal as the amplification value changes between the first threshold and the second threshold.

15. The defog method of claim 13 , wherein the outputting the respective defog level signal comprises reducing the respective defog level signal as the amplification value changes from the first threshold to the second threshold.

16. The defog method of claim 9 , further comprising:

detecting an edge amount of the input image; and

in response to the edge amount being less than or equal to a threshold, applying a gamma curve to the defogged input image based on a relationship between the edge amount and a preset luminance.