Method of multi-frame image noise reduction

摘要

A method of multi-frame image noise reduction suitable for an image-capturing device includes following steps: obtaining a current frame and multiple reference frames; defining a mask and a target point in the mask; judging whether the target point pixel of the current frame is on an edge according to an edge map of the frame; when the pixel is on the edge, using the pixels in the reference frames on the edge to calculate a replacement result; when the target point pixel is not on the edge, using the pixels in the reference frames surrounding the target point to calculate a replacement result; after that, generating a pixel corresponding to the position of the target point in an output image according to the replacement result; further, moving the mask and going back to judge whether the pixel of the target point of the current frame is on the edge.

主权项

1. A method of multi-frame image noise reduction, suitable for an image-capturing device and comprising:
obtaining a current frame and a plurality of reference frames; defining a mask and a target point in the mask, wherein a plurality of same positions of the current frame and the reference frames are marked by the mask after motion compensation is performed on the current frame and the reference frames; judging whether or not the pixel of the target point of the current frame is located on at least one edge of the current frame according to an edge map of the current frame, wherein the at least one edge comprises a first edge which is corresponding to a plurality of second edge of the reference frames, and each of the second edges is respectively located on each of the reference frames; when the pixel of the target point is located on the first edge, calculating a replacement result by using the pixels the reference frames respectively located on each of the second edges, wherein the pixels on the second edges in the references frames correspond to the same spatial position as the target point in the current frame; when the pixel of the target point is not located on the first edge, calculating a replacement result by using the pixels in the mask of each of the reference frames corresponding to pixels surrounding the target point and on a same side of the second edge as the target point location with respect to the first edge; generating a pixel corresponding to the position of the target point in an output image according to the replacement result; and moving the mask and going back to the step of judging whether or not the pixel of the target point of the current frame is located on the at least one edge, wherein the step of calculating the replacement result by using the pixels in the reference frames respectively located on each of the second edges comprises: determining a representing direction of the first edge and the second edges among a plurality of edge directions according to the contrast of the pixel of the target point over the adjacent pixels; respectively calculating a median value of the pixels of the current frame on the representing direction and calculating median values for each of the reference frames using the pixels of each of the reference frames on the representing direction; and determining the replacement result according to the median values.