Defective pixel correction device and method of operating the same
A defective pixel correction device is provided. The defective pixel correction device includes: a pixel grading circuit configured to output a grade map including a plurality of grades indicating defect levels and respectively corresponding to a plurality of pixels included in an input image; a pixel selection circuit configured to select one or more candidate pixels from among the plurality of pixels, based on whether the plurality of grades correspond to a correction level, in the grade map; and a correction circuit configured to correct the one or more candidate pixels.
1 . A defective pixel correction device comprising:
a pixel grading circuit configured to output a grade map comprising a plurality of grades indicating defect levels and respectively corresponding to a plurality of pixels included in an input image, wherein the plurality of pixels comprises red pixels, green pixels and blue pixels arranged in a regular pattern;
a pixel selection circuit configured to select one or more candidate pixels from among the plurality of pixels, based on whether the plurality of grades correspond to a correction level, in the grade map; and
a correction circuit configured to:
calculate one or more correction values based on the one or more candidate pixels and a plurality of neighboring pixels included in an image patch, wherein the image patch includes the one or more candidate pixels;
correct the one or more candidate pixels based on the one or more correction values; and
replicate the image patch for each of the one or more candidate pixels.
2 . The defective pixel correction device of claim 1 , wherein the pixel grading circuit is further configured to assign a grade to a target pixel of the plurality of pixels based on an average value or a median value of a plurality of neighboring pixels included in an image patch being compared with a pixel value of the target pixel.
3 . The defective pixel correction device of claim 2 , wherein the pixel grading circuit is further configured to:
assign a first grade as the grade of the target pixel based on satisfaction of a first condition in which a difference between the pixel value and the average value or the median value is less than a first threshold value;
assign a third grade as the grade of the target pixel based on satisfaction of a second condition in which the difference between the pixel value and the average value or the median value is greater than a second threshold value; and
assign a second grade as the grade of the target pixel based on the target pixel satisfying neither the first condition nor the second condition.
4 . The defective pixel correction device of claim 3 , wherein the correction level comprises at least one of the second grade and the third grade.
5 . The defective pixel correction device of claim 1 , wherein the pixel selection circuit is further configured to set at least one of the plurality of grades to the correction level based on a ratio of one of the plurality of grades in the grade map to another one of the plurality of grades in the grade map.
6 . The defective pixel correction device of claim 1 , wherein the correction circuit is further configured to calculate the one or more correction values for the one or more candidate pixels and the correcting for the one or more candidate pixels in parallel.
7 . The defective pixel correction device of claim 1 , further comprising a replication circuit configured to select one of a correction value and a reference value for each of the one or more candidate pixels.
8 . The defective pixel correction device of claim 7 , wherein the replication circuit is further configured to:
compare a first difference between one or more pixel values of the one or more candidate pixels before being corrected and the correction value, and a second difference between the one or more pixel values and the reference value; and
select the correction value based on the first difference being greater than the second difference, and select the reference value based on the first difference not being greater than the second difference.
9 . The defective pixel correction device of claim 1 , wherein the regular pattern is a Bayer pattern.
10 . A method of operating a defective pixel correction device, the method comprising:
assigning a plurality of grades, among grades indicating defect levels, to a plurality of pixels included in an input image, respectively, wherein the plurality of pixels comprises red pixels, green pixels and blue pixels arranged in a regular pattern;
outputting a grade map comprising the plurality of grades;
selecting one or more candidate pixels from among the plurality of pixels, based on whether the plurality of grades correspond to a correction level, in the grade map;
correcting the one or more candidate pixels;
replicating an image patch for each of the one or more candidate pixels; and
calculating one or more correction values based on the one or more candidate pixels and a plurality of neighboring pixels included in the image patch.
11 . The method of claim 10 , further comprising:
setting at least one of the plurality of grades to the correction level;
determining which of the plurality of grades correspond to the correction level; and
selecting the one or more candidate pixels based on which of the plurality of grades correspond to the correction level.
12 . The method of claim 10 , further comprising:
receiving a reference value for the one or more candidate pixels;
calculating a first difference between one or more pixel values of the one or more candidate pixels before being corrected and correction value of the one or more correction values, and a second difference between the one or more pixel values of the one or more candidate pixels before being corrected and the reference value; and
selecting the correction value based on the first difference being greater than the second difference, and selecting the reference value based on the first difference not being greater than the second difference.
13 . The method of claim 10 , wherein the calculating the one or more correction values and the correcting are performed for the one or more candidate pixels in parallel.
14 . The method of claim 11 , wherein the correction level is set based on a ratio of each of the plurality of grades in the grade map.
15 . An electronic device comprising:
an image sensor comprising red pixels, green pixels and blue pixels arranged in a regular pattern;
a pixel grading circuit configured to output a grade map comprising a plurality of pixels to which a grade, among a plurality of grades indicating defect levels, is assigned, based on the grade being assigned, wherein the plurality of pixels are included in an input image output from the image sensor;
a pixel selection circuit configured to select one or more candidate pixels, having the grade corresponding to a correction level, in the grade map; and
a correction circuit configured to:
calculate one or more correction values based on the one or more candidate pixels and a plurality of neighboring pixels included in an image patch, wherein the image patch includes the one or more candidate pixels;
correct the one or more candidate pixels based on the one or more correction values; and
replicate the image patch for each of the one or more candidate pixels.
16 . The electronic device of claim 15 , wherein the pixel selection circuit is further configured to set at least one of the plurality of grades to the correction level based on a ratio of one of the plurality of grades in the grade map to another one of the plurality of grades in the grade map.