Image processing device, image processing method, image processing program, and recording medium
The image processing device performs noise removal processing for an input image. The image processing device comprises a filter setting unit configured to set first and second filter factors by using a first target pixel value of a noise processing target pixel to be targeted to the processing and a reference pixel value of a plurality of reference pixels surrounding the noise processing target pixel and a noise removal unit configured to calculate a corrected pixel value by sequentially adding a luminance component of the reference pixel value weighted with the first filter factor and sequentially adding a chroma component of the reference pixel value weighted with the second filter factor, and remove noise of the noise processing target pixel by using the corrected pixel value. The input image has pixel values according to Bayer pattern format.
1. An image processing device for performing noise removal processing for an input image comprising image pixels, the image processing device comprising:
a buffer configured to store pixel values of the image pixels according to Bayer pattern format, wherein one or more of the image pixels are selectable as an abnormality processing target pixel having a target pixel value;
a processor; and
a memory device storing executable instructions that, when executed by the processor, cause the processor to:
calculate each of a plurality of estimated pixel values for the abnormality processing target pixel based, at least in part, on one or more of the image pixels that are linearly arranged with the abnormality processing target pixel;
perform a plurality of comparisons of the target pixel value of the abnormality processing target pixel with the plurality of estimated pixel values to determine, based on the plurality of comparisons, whether or not the target pixel value is abnormal; and
substitute the target pixel value with one of the plurality of the estimated pixel values when the target pixel value is determined to be abnormal based on the plurality of comparisons.
2. The image processing device according to claim 1 , wherein the plurality of comparisons are performed by:
comparing the target pixel value of the abnormality processing target pixel with the plurality of estimated pixel values, to determine a divergence number representing a number of comparison results indicating that the target pixel value is divergent relative to a respective one of the plurality of estimated pixel values; and
determining whether or not the target pixel value is abnormal based on the divergence number.
3. The image processing device according to claim 2 , wherein the executable instructions stored in the memory device further cause the processor to:
extract an area of the image pixels including the abnormality processing target pixel;
calculate a variance in pixels values, associated with the area extracted; and
set a first threshold based at least in part on the variance, wherein the divergence number is obtained by calculating a difference between the target pixel value of the abnormality processing target pixel and each of the plurality of estimated pixel values to obtain respective differences, and setting the divergence number to a number of the differences exceeding the first threshold.
4. The image processing device according to claim 2 , wherein the executable instructions stored in the memory device further cause the processor to:
extract an area of the image pixels including the abnormality processing target pixel; and
set a second threshold based on a determination as to whether the area includes an edge of the input image, wherein the divergence number is compared to the second threshold to determine whether or not the target pixel value is abnormal.
5. The image processing device according to claim 4 , wherein the second threshold is set higher when the area includes the edge.
6. The image processing device according to claim 4 , wherein the second threshold is greater than one.
7. The image processing device according to claim 1 wherein, for each of the plurality of estimated pixel values that are calculated for the abnormality processing target pixel, the one or more image pixels are linearly arranged in a predetermined direction.