Apparatuses and methods for noise reduction
View Patent ↗Methods and apparatuses provide noise reduction in a demosaiced digital image by processing the digitized signals received from a color pattern pixel array for noise reduction previous to, or as part of, a demosaicing process by using a weight matrix.
1. A method of processing a digital image, said method comprising:
capturing an image from a Bayer patterned pixel array;
providing digital Bayer pattern pixel signals corresponding to the pixels of said array;
demosaicing said digital Bayer pattern pixel signals to produce said digital image;
removing noise from said digital Bayer pattern pixel signals prior to or as part of said demosaicing by using a weight matrix, wherein said step of removing noise further comprises:
calculating a plurality of differences between a center pixel being processed and a plurality of surrounding pixels;
counting each of the plurality of differences whose value is less than a first threshold to obtain a count; and
processing the center pixel based on weighted values for the center pixel and the plurality of surrounding pixels obtained from the weight matrix, wherein the weighted values are determined by using a row of the weight matrix corresponding to the count, and wherein the weight matrix comprises:
[
1
1
1
1
1
1
1
1
/
2
1
/
2
1
1
1
1
1
1
1
1
0
2
1
1
1
1
1
1
0
0
2
2
1
1
1
1
0
0
0
2
2
2
1
1
0
0
0
0
2
2
2
2
0
0
0
0
0
4
2
2
0
0
0
0
0
0
4
4
0
0
0
0
0
0
0
8
0
0
0
0
0
0
0
0
0
2
2
2
2
0
0
0
0
]
.
2. A method of processing a digital image, said method comprising:
capturing an image from a Bayer patterned pixel array;
providing digital Bayer pattern pixel signals corresponding to the pixels of said array;
demosaicing said digital Bayer pattern pixel signals to produce said digital image;
removing noise from said digital Bayer pattern pixel signals prior to or as part of said demosaicing by using a weight matrix, wherein said step of removing noise further comprises:
calculating a plurality of differences between a center pixel being processed and a plurality of surrounding pixels;
counting each of the plurality of differences whose value is less than a first threshold to obtain a count; and
processing the center pixel based on weighted values for the center pixel and the plurality of surrounding pixels obtained from the weight matrix, wherein the weighted values are determined by using a row of the weight matrix corresponding to the count, and wherein the weight matrix comprises:
[
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
2
2
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
2
2
2
1
1
1
1
1
1
1
1
1
1
0
0
0
0
2
2
2
2
1
1
1
1
1
1
1
1
0
0
0
0
0
2
2
2
2
2
1
1
1
1
1
1
0
0
0
0
0
0
2
2
2
2
2
2
1
1
1
1
0
0
0
0
0
0
0
2
2
2
2
2
2
2
1
1
0
0
0
0
0
0
0
0
2
2
2
2
2
2
2
2
0
0
0
0
0
0
0
0
0
4
2
2
2
2
2
2
0
0
0
0
0
0
0
0
0
0
4
4
2
2
2
2
0
0
0
0
0
0
0
0
0
0
0
4
4
4
2
2
0
0
0
0
0
0
0
0
0
0
0
0
4
4
4
4
0
0
0
0
0
0
0
0
0
0
0
0
0
8
4
4
0
0
0
0
0
0
0
0
0
0
0
0
0
0
8
8
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
16
0
0
0
0
0
0
0
0
0
0
0
0
0
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0
0
0
4
4
4
4
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0
0
0
0
0
0
0
0
0
0
]
.
3. An apparatus for processing a digital image, said apparatus comprising:
a digital image processor configured to perform the steps of:
capturing an image from a Bayer patterned pixel array;
providing digital Bayer pattern pixel signals corresponding to the pixels of said array; and
demosaicing or processing said digital Bayer pattern pixel signals with a weight matrix to both remove noise and demosaic the signals, wherein said step of removing noise further comprises:
calculating a plurality of differences between a center pixel being processed and a plurality of surrounding pixels;
counting each of the plurality of differences whose value is less than a first threshold to obtain a count; and
processing the center pixel based on weighted values for the center pixel and the plurality of surrounding pixels, said weighted values determined by using a row of the weight matrix corresponding to the count, the matrix having rows and columns, and each row having a plurality of entries, wherein the number of rows in the weight matrix is two more than the number of surrounding pixels, the number of columns in the weight matrix is one more than the number of surrounding pixels, the total value of each row of the weight matrix is the number of surrounding pixels, the entries in each row of the weight matrix are in descending order, at least one row of the weight matrix comprises a number of zeroes that is one more than the number of zeroes in the previous row, and wherein the last row in the weight matrix comprises:
a first entry equal to 0;
a second, third, fourth and fifth entry each equal to the number of surrounding pixels divided by 4; and
a sixth through a last entry equal to zero.