这是我们在kWave工具箱中使用的resize函数。

function mat_rs = resize(varargin)

%RESIZE Resize a matrix.

% DESCRIPTION:

% Resize a matrix to a given size using interp2 (2D) or interp3

% (3D).

% Use interpolation to redivide the [0,1] interval into Nx, Ny, Nz

% voxels, where 0 is the center of first voxel, and 1 is the center

% of the last one.

%

% USAGE:

% mat_rs = resize(mat, new_size)

% mat_rs = resize(mat, new_size, interp_mode)

%

% INPUTS:

% mat - matrix to resize

% new_size - desired matrix size in elements given by [Nx, Ny] in

% 2D and [Nx, Ny, Nz] in 3D. Here Nx is the number of

% elements in the row direction, Ny is the number of

% elements in the column direction, and Nz is the

% number of elements in the depth direction.

%

% OPTIONAL INPUTS:

% interp_mode - interpolation mode used by interp2 and interp3

% (default = '*linear')

%

% OUTPUTS:

% mat_rs - resized matrix

% check the inputs for release B.0.2 compatability

if length(varargin{2}) == 1 && nargin >= 3 && length(varargin{3}) == 1

% display warning message

disp('WARNING: input usage deprecated, please see documentation.');

disp('In future releases this usage will no longer be functional.');

% recursively call resize with the correct inputs

if nargin == 3

mat_rs = resize(varargin{1}, [varargin{2}, varargin{3}]);

else

mat_rs = resize(varargin{1}, [varargin{2}, varargin{3}], varargin{4});

end

return

end

% update command line status

disp('Resizing matrix...');

% assign the matrix input

mat = varargin{1};

% check for interpolation mode input

if nargin == 2

interp_mode = '*linear';

elseif nargin ~= 3

error('incorrect number of inputs');

else

interp_mode = varargin{3};

end

% check inputs

if numDim(mat) ~= length(varargin{2})

error('resolution input must have the same number of elements as data dimensions');

end

switch numDim(mat)

case 2

% extract the original number of pixels from the size of the matrix

[Nx_input, Ny_input] = size(mat);

% extract the desired number of pixels

Nx_output = varargin{2}(1);

Ny_output = varargin{2}(2);

% update command line status

disp([' input grid size: ' num2str(Nx_input) ' by ' num2str(Ny_input) ' elements']);

disp([' output grid size: ' num2str(Nx_output) ' by ' num2str(Ny_output) ' elements']);

% check the size is different to the input size

if Nx_input ~= Nx_output || Ny_input ~= Ny_output

% resize the input matrix to the desired number of pixels

mat_rs = interp2(0:1/(Ny_input - 1):1, (0:1/(Nx_input - 1):1)', mat, 0:1/(Ny_output - 1):1, (0:1/(Nx_output - 1):1)', interp_mode);

else

mat_rs = mat;

end

case 3

% extract the original number of pixels from the size of the matrix

[Nx_input, Ny_input, Nz_input] = size(mat);

% extract the desired number of pixels

Nx_output = varargin{2}(1);

Ny_output = varargin{2}(2);

Nz_output = varargin{2}(3);

% update command line status

disp([' input grid size: ' num2str(Nx_input) ' by ' num2str(Ny_input) ' by ' num2str(Nz_input) ' elements']);

disp([' output grid size: ' num2str(Nx_output) ' by ' num2str(Ny_output) ' by ' num2str(Nz_output) ' elements']);

% create normalised plaid grids of current discretisation

[x_mat, y_mat, z_mat] = ndgrid((0:Nx_input-1)/(Nx_input-1), (0:Ny_input-1)/(Ny_input-1), (0:Nz_input-1)/(Nz_input-1));

% create plaid grids of desired discretisation

[x_mat_interp, y_mat_interp, z_mat_interp] = ndgrid((0:Nx_output-1)/(Nx_output-1), (0:Ny_output-1)/(Ny_output-1), (0:Nz_output-1)/(Nz_output-1));

% compute interpolation; for a matrix indexed as [M, N, P], the

% axis variables must be given in the order N, M, P

mat_rs = interp3(y_mat, x_mat, z_mat, mat, y_mat_interp, x_mat_interp, z_mat_interp, interp_mode);

otherwise

error('input matrix must be 2 or 3 dimensional');

end