双边滤波Matlab代码

%简单地说:

%A为给定图像，归一化到[0,1]的矩阵

%W为双边滤波器（核）的边长/2

%定义域方差σd记为SIGMA(1),值域方差σr记为SIGMA(2)

 

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Pre-process input and select appropriate filter.

function B = bfilter2(A,w,sigma)

 

% Verify that the input image exists and is valid.

if ~exist('A','var') || isempty(A)

   error('Input image A is undefined or invalid.');

end

if ~isfloat(A) || ~sum([1,3] == size(A,3)) || ...

      min(A(:)) < 0 || max(A(:)) > 1

   error(['Input image A must be a double precision ',...

          'matrix of size NxMx1 or NxMx3 on the closed ',...

          'interval [0,1].']);      

end

 

% Verify bilateral filter window size.

if ~exist('w','var') || isempty(w) || ...

      numel(w) ~= 1 || w < 1

   w = 5;

end

w = ceil(w);

 

% Verify bilateral filter standard deviations.

if ~exist('sigma','var') || isempty(sigma) || ...

      numel(sigma) ~= 2 || sigma(1) <= 0 || sigma(2) <= 0

   sigma = [3 0.1];

end

 

% Apply either grayscale or color bilateral filtering.

if size(A,3) == 1

   B = bfltGray(A,w,sigma(1),sigma(2));

else

   B = bfltColor(A,w,sigma(1),sigma(2));

end

 

 

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Implements bilateral filtering for grayscale images.

function B = bfltGray(A,w,sigma_d,sigma_r)

 

% Pre-compute Gaussian distance weights.

[X,Y] = meshgrid(-w:w,-w:w);

%创建核距离矩阵，e.g.

%  [x,y]=meshgrid(-1:1,-1:1)

% 

% x =

% 

%     -1     0     1

%     -1     0     1

%     -1     0     1

% 

% 

% y =

% 

%     -1    -1    -1

%      0     0     0

%      1     1     1

%计算定义域核

G = exp(-(X.^2+Y.^2)/(2*sigma_d^2));

 

% Create waitbar.

h = waitbar(0,'Applying bilateral filter...');

set(h,'Name','Bilateral Filter Progress');

 

% Apply bilateral filter.

%计算值域核H 并与定义域核G 乘积得到双边权重函数F

dim = size(A);

B = zeros(dim);

for i = 1:dim(1)

   for j = 1:dim(2)

      

         % Extract local region.

         iMin = max(i-w,1);

         iMax = min(i+w,dim(1));

         jMin = max(j-w,1);

         jMax = min(j+w,dim(2));

         %定义当前核所作用的区域为(iMin:iMax,jMin:jMax)

         I = A(iMin:iMax,jMin:jMax);%提取该区域的源图像值赋给I

      

         % Compute Gaussian intensity weights.

         H = exp(-(I-A(i,j)).^2/(2*sigma_r^2));

      

         % Calculate bilateral filter response.

         F = H.*G((iMin:iMax)-i+w+1,(jMin:jMax)-j+w+1);

         B(i,j) = sum(F(:).*I(:))/sum(F(:));

               

   end

   waitbar(i/dim(1));

end

 

% Close waitbar.

close(h);

 

 

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Implements bilateral filter for color images.

function B = bfltColor(A,w,sigma_d,sigma_r)

 

% Convert input sRGB image to CIELab color space.

if exist('applycform','file')

   A = applycform(A,makecform('srgb2lab'));

else

   A = colorspace('Lab<-RGB',A);

end

 

% Pre-compute Gaussian domain weights.

[X,Y] = meshgrid(-w:w,-w:w);

G = exp(-(X.^2+Y.^2)/(2*sigma_d^2));

 

% Rescale range variance (using maximum luminance).

sigma_r = 100*sigma_r;

 

% Create waitbar.

h = waitbar(0,'Applying bilateral filter...');

set(h,'Name','Bilateral Filter Progress');

 

% Apply bilateral filter.

dim = size(A);

B = zeros(dim);

for i = 1:dim(1)

   for j = 1:dim(2)

      

         % Extract local region.

         iMin = max(i-w,1);

         iMax = min(i+w,dim(1));

         jMin = max(j-w,1);

         jMax = min(j+w,dim(2));

         I = A(iMin:iMax,jMin:jMax,:);

      

         % Compute Gaussian range weights.

         dL = I(:,:,1)-A(i,j,1);

         da = I(:,:,2)-A(i,j,2);

         db = I(:,:,3)-A(i,j,3);

         H = exp(-(dL.^2+da.^2+db.^2)/(2*sigma_r^2));

      

         % Calculate bilateral filter response.

         F = H.*G((iMin:iMax)-i+w+1,(jMin:jMax)-j+w+1);

         norm_F = sum(F(:));

         B(i,j,1) = sum(sum(F.*I(:,:,1)))/norm_F;

         B(i,j,2) = sum(sum(F.*I(:,:,2)))/norm_F;

         B(i,j,3) = sum(sum(F.*I(:,:,3)))/norm_F;

                

   end

   waitbar(i/dim(1));

end

 

% Convert filtered image back to sRGB color space.

if exist('applycform','file')

   B = applycform(B,makecform('lab2srgb'));

else  

   B = colorspace('RGB<-Lab',B);

end

 

% Close waitbar.

close(h);