CN102801983A - Denoising method and device on basis of DCT (Discrete Cosine Transform) - Google Patents
Denoising method and device on basis of DCT (Discrete Cosine Transform) Download PDFInfo
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- CN102801983A CN102801983A CN2012103125438A CN201210312543A CN102801983A CN 102801983 A CN102801983 A CN 102801983A CN 2012103125438 A CN2012103125438 A CN 2012103125438A CN 201210312543 A CN201210312543 A CN 201210312543A CN 102801983 A CN102801983 A CN 102801983A
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Abstract
The invention discloses a denoising method and a denoising device on the basis of DCT (Discrete Cosine Transform). The method comprises the following steps: setting an initial block selection center and a denoising threshold value; selecting a block with the size of m*m by taking the set block selection center as the center; carrying out m*m DCT transformation on the block; judging a value obtained after DCT transformation, if absolute values of the rest of m*m-1 AC (Alternate Current) DCT coefficients are less than the denoising threshold value except for a DC (Direct Current) DCT coefficient, using an average value of all values in the block as a filtered value at the position of the block selection center, or filtering by a conventional filtering method; and changing an abscissa and an ordinate of the block selection center and repeating the steps. By the denoising method and the denoising device on the basis of DCT, noise can be well eliminated on flat regions of an image and a video and details of the image and the video are kept in regions with the rich details.
Description
Technical field
The present invention relates to a kind of denoising method and device, particularly relate to a kind of denoising method and device based on DCT to additive white noise based on DCT (Discrete Cosine Transform, discrete cosine transform).
Background technology
In image and video, often there is noise, wherein white Gaussian noise is main noise type.White Gaussian noise is two types of branch additivity and the property taken advantage of again, and so-called additivity is exactly that the value of noise and the content of image or video have nothing to do, and can regard final image or vision signal as that real image or vision signal and noise signal addition obtain.The what is called property taken advantage of, the value that is exactly noise is relevant with the content of image or video.The characteristics of white Gaussian noise are to obey the normal distribution of 0 average.
The method of elimination noise in the past basically all is under the prerequisite of the characteristic of not knowing noise, to handle, and therefore is difficult to accomplish accurately and targetedly the details that when eliminating noise, can lose image.
Summary of the invention
For overcoming the deficiency that above-mentioned prior art exists; The present invention's purpose is to provide a kind of denoising method and device based on DCT; Its noise in known image or video is that standard deviation is under the prerequisite of additive white Gaussian noise of sigma; Propose a kind of method of eliminating noise, can well eliminate noise, keep the details of image and video simultaneously in the abundant zone of details at the flat site of image and video.
For reaching above-mentioned and other purpose, the present invention provides a kind of denoising method based on DCT, is used for the noise of removal of images or the arbitrary component of frame of video, comprises the steps:
Step 1 is set initial square and is chosen center and noise-removed threshold value;
Step 2, choosing the center with the square of setting is that the square that size is m*m is chosen at the center;
Step 3 is carried out the m*m dct transform to this square;
Step 4 is judged the value behind dct transform, and except that direct current DCT coefficient, all less than this noise-removed threshold value, the mean value of then getting all values in this square is chosen the filtered value of center as this square as if all the other m*m-1 the absolute values that exchange the DCT coefficients; Otherwise, carry out filtering with traditional filtering method;
Step 5 changes abscissa and ordinate that this square is chosen the center, if square is chosen all positions that the center has traveled through this component of image or frame of video, then finishes the denoising process; Otherwise forward step 2 to.
Further, other components to pending image or frame of video repeat step 1 to step 5, to this pending image or frame of video denoising.
Further, it is (0,0) that initial square is selected the coordinate at center, and noise-removed threshold value is k*sigma, and wherein k is a positive number, and sigma is that noise criteria is poor.
Further, 2.0＜k＜5.0.
Further, in step 2, choosing the center with the square of setting is that the square that size is 8*8 is chosen at the center.
For reaching above-mentioned and other purposes, the present invention also provides a kind of denoising device based on DCT, is used for the noise of removal of images or the arbitrary component of frame of video, comprises at least:
Initialization module is used to set initial square and chooses center and noise-removed threshold value;
Square is chosen module, and choosing the center with the square of setting is the center, gets size and is the square of m*m;
The dct transform module is carried out the dct transform of m*m to this square;
The denoising module is carried out corresponding denoising operation according to the result of dct transform; And
Square is chosen the center and is changed module, changes abscissa and ordinate that square is chosen the center.
Further; This denoising module is judged the value behind dct transform; Except that direct current DCT coefficient, all less than this noise-removed threshold value, the mean value of then getting all values in this square is chosen the filtered value of center as this square as if all the other m*m-1 the absolute values that exchange the DCT coefficients; Otherwise, carry out filtering with traditional filtering method.
Further, this square is chosen the center and is changed in the module, after this square is chosen all positions of this component that the center travel through image or frame of video, and end denoising process.
Further, this square is chosen module, and choosing the center with the square of setting is the center, gets size and is the square of 8*8.
Further, the coordinate that this initialization module is set initial square selection center is (0,0), and noise-removed threshold value is k*sigma, and wherein k is a positive number, and sigma is that noise criteria is poor.
Compared with prior art, the present invention a kind of denoising method and device based on DCT are through with point (x0; Y0) choose the square of m*m for the center; Square is carried out behind the dct transform numerical value behind the dct transform is judged with to point (x0, y0) denoising, the not only additive white Gaussian noise in removal of images or the frame of video effectively; And can well eliminate noise at the flat site of image and video, keep the details of image and video simultaneously in the abundant zone of details.
Description of drawings
Fig. 1 is the flow chart of steps of a kind of denoising method based on DCT of the present invention;
Fig. 2 is for being the sketch map that the 8*8 square is got at the center with a point in the preferred embodiment of a kind of denoising method based on DCT of the present invention;
Fig. 3 is the system architecture diagram of a kind of denoising device based on DCT of the present invention.
Embodiment
Below through specific instantiation and accompanying drawings execution mode of the present invention, those skilled in the art can understand other advantage of the present invention and effect easily by the content that this specification disclosed.The present invention also can implement or use through other different instantiation, and each item details in this specification also can be based on different viewpoints and application, carries out various modifications and change under the spirit of the present invention not deviating from.
Suppose that pending image or frame of video are f={f [0], f [1], f [2] }, wherein f [j] is j component (coloured image has three components, and black and white image has only one-component).F [j]={ f [j] [y] [x] }, the wherein sampled value of the capable x row of j branch flow control y of f [j] [y] [x] expression.X, the span of y be [0, w
j-1] and [0, h
j-1], wj and h
jBe respectively the width and the height of j component of image.
Fig. 1 is the flow chart of steps of a kind of denoising method based on DCT of the present invention.As shown in Figure 1, a kind of denoising method based on DCT of the present invention is used for the additive white Gaussian noise of the arbitrary component f of removal of images or frame of video [j], comprises the steps:
If y＜0 makes a=0; If y＞h
j-1, make a=h
j-1, otherwise make a=y;
If x＜0 makes d=0, if x＞w
j-1, make d=w
j-1, otherwise make d=x.
At this, what need explanation is, the process of noise is duplicate in each component of removal of images or frame of video, and above step 101 to step 105 is recycled and reused for each component, just can removal of images or frame of video in noise.
Below will further specify the present invention through a specific embodiment.In preferred embodiment of the present invention, the square of choosing 8*8 is carried out denoising, the method for the additive white Gaussian noise of arbitrary component f [j] comprises the steps: in removal of images or the frame of video
1) make x0=0, y0=0, t=k*sigma, wherein k is a positive number, general 2.0＜k＜5.0.
2) as shown in Figure 2, so that (x0 y0) gets size for the square of 8*8 for the center, is designated as B.B={b [y] [x]=f [j] [a] [d] | y0-3≤y≤y0+4, x0-3≤x≤x0+4; If y＜0 makes a=0,, otherwise make a=y if y＞hj-1 makes a=hj-1; If x＜0 makes d=0,, otherwise make d=x} if x＞wj-1 makes d=wj-1.
3) square B is carried out the 8*8DCT conversion, the conversion postscript is C={c [yc] [xc]; Yc=0..7, xc=0..7}.
4) except direct current DCT coefficient c [0] [0]; If all the other 63 absolute values that exchange the DCT coefficient are all less than t among the C; The mean value of then getting all values among the piece B is as (x0, the filtered value of y0) locating, otherwise carry out filtering with traditional filtering method (template of for example getting 3x3 is carried out weighted filtering).
5)x0++。If x0 equals w
j, then make x0=0, y0++.If y0 equals h
j, then finish, otherwise forward step 2 to).
Fig. 3 is the system architecture diagram of a kind of denoising device based on DCT of the present invention.A kind of denoising device of the present invention as shown in Figure 3 based on DCT; Be used for the additive white Gaussian noise of the arbitrary component f of removal of images or frame of video [j], comprise at least: initialization module 301, square are chosen module 302, dct transform module 303, denoising module 304 and square and are chosen center change module 305.
Wherein initialization module 301 is used to carry out initializing set, promptly set initial square choose the center (x0 y0) and noise-removed threshold value t, that is: makes x0=0, y0=0, t=k*sigma, wherein k is a positive number, sigma is that noise criteria is poor; Square is chosen module 302, and choosing the center with the square of setting is the center, gets size for the square of 8*8, is designated as B.B={b [y] [x]=f [j] [a] [d] | y0-3≤y≤y0+4, x0-3≤x≤x0+4; If y＜0 makes a=0,, otherwise make a=y if y＞hj-1 makes a=hj-1; If x＜0 makes d=0,, otherwise make d=x} if x＞wj-1 makes d=wj-1.
Dct transform module 303 is used for square B is carried out the dct transform of m*m (like 8*8), obtains DCT coefficient matrix C, and DCT coefficient matrix C is designated as C={c [yc] [xc] after the conversion; Yc=0..7, xc=0..7}.
Denoising module 304 is carried out corresponding denoising operation according to the result of dct transform.Promptly except direct current DCT coefficient c [0] [0]; If all the other 63 absolute values that exchange the DCT coefficient are all less than t among the C; The mean value of then getting all values among the square B is as (x0; Y0) the filtered value of locating, otherwise carry out filtering with traditional filtering method, traditional filtering method carries out weighted filtering etc. like the template of getting 3*3.
Square is chosen the center and is changed module 305, changes square and chooses the abscissa x0 and the ordinate y0 at center, and judge whether whole positions of this component of traversing graph picture or frame of video.That is: if x0++ is x0>=w
j, then make x0=0, y0++; If y0>=h
j, then finish, otherwise square is chosen module 302 and is continued to choose square.
It is thus clear that the present invention a kind of denoising method and device based on DCT are through with point (x0; Y0) choose the square of 8*8 for the center; Square is carried out behind the dct transform numerical value behind the dct transform is judged with to point (x0, y0) denoising, the not only additive white Gaussian noise in removal of images or the frame of video effectively; And can well eliminate noise at the flat site of image and video, keep the details of image and video simultaneously in the abundant zone of details.
The foregoing description is illustrative principle of the present invention and effect thereof only, but not is used to limit the present invention.Any those skilled in the art all can be under spirit of the present invention and category, and the foregoing description is modified and changed.Therefore, rights protection scope of the present invention should be listed like claims.
Claims (10)
1. denoising method based on DCT is used for the noise of removal of images or the arbitrary component of frame of video, comprises the steps:
Step 1 is set initial square and is chosen center and noise-removed threshold value;
Step 2, choosing the center with the square of setting is that the square that size is m*m is chosen at the center;
Step 3 is carried out the m*m dct transform to this square;
Step 4 is judged the value behind dct transform, and except that direct current DCT coefficient, all less than this noise-removed threshold value, the mean value of then getting all values in this square is chosen the filtered value of center as this square as if all the other m*m-1 the absolute values that exchange the DCT coefficients; Otherwise, carry out filtering with traditional filtering method;
Step 5 changes abscissa and ordinate that this square is chosen the center, if square is chosen all positions that the center has traveled through this component of image or frame of video, then finishes, otherwise forwards step 2 to.
2. a kind of denoising method based on DCT as claimed in claim 1 is characterized in that: other components to pending image or frame of video repeat step 1 to step 5, to this pending image or frame of video denoising.
3. a kind of denoising method based on DCT as claimed in claim 1 is characterized in that: it is (0,0) that initial square is selected the coordinate at center, and noise-removed threshold value is k*sigma, and wherein k is a positive number, and sigma is that noise criteria is poor.
4. a kind of denoising method based on DCT as claimed in claim 1 is characterized in that, in step 2; With square choose the center (x0, y0) to choose size following for the method for the square of m*m for the center: when m was odd number, m can be expressed as 2k+1; K is a positive integer, and selected square is:
B＝{b[y][x]|y0-k≤y≤y0+k，x0-k≤x≤x0+k；}
When m was even number, m can be expressed as 2k, and k is a positive integer, and selected square is:
B＝{b[y][x]|y0-k+1≤y≤y0+k，x0-k+1≤x≤x0+k；}
Wherein, b [y] [x] represent this image or frame of video component in coordinate (x, the value of y) locating; As (x; When y) exceeding the span that the component of this image or frame of video allows, get in the span of permission with (x, y) value at nearest coordinate place is as the value of b [y] [x].
5. a kind of denoising method based on DCT as claimed in claim 1 is characterized in that: in step 2, choosing the center with the square of setting is that the square that size is 8*8 is chosen at the center.
6. denoising device based on DCT, the noise that is used for removal of images or the arbitrary component of frame of video comprises at least:
Initialization module is used to set initial square and chooses center and noise-removed threshold value;
Square is chosen module, and choosing the center with the square of setting is the center, gets size and is the square of m*m;
The dct transform module is carried out the dct transform of m*m to this square;
The denoising module is carried out corresponding denoising operation according to the result of dct transform; And
Square is chosen the center and is changed module, changes abscissa and ordinate that square is chosen the center.
7. a kind of denoising device as claimed in claim 6 based on DCT; It is characterized in that: this denoising module is judged the value behind dct transform; Except that direct current DCT coefficient; If all the other m*m-1 the absolute values that exchange the DCT coefficient are all less than this noise-removed threshold value, the mean value of then getting all values in this square is chosen the filtered value of center as this square; Otherwise, carry out filtering with traditional filtering method.
8. a kind of denoising device based on DCT as claimed in claim 6 is characterized in that: this square is chosen the center and is changed in the module, after this square is chosen all positions of this component that the center travel through image or frame of video, and end denoising process.
9. a kind of denoising device as claimed in claim 6 based on DCT, it is characterized in that: this square is chosen module, and choosing the center with the square of setting is the center, gets size and is the square of 8*8.
10. a kind of denoising device based on DCT as claimed in claim 6 is characterized in that: the coordinate that this initialization module is set initial square selection center is (0,0), and noise-removed threshold value is k*sigma, and wherein k is a positive number, and sigma is that noise criteria is poor.
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Application publication date: 20121128 |