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Function List:

C++ API

Function File: filter = fspecial( type, arg1, arg2)

Create spatial filters for image processing.

type determines the shape of the filter and can be

"average"

Rectangular averaging filter. The optional argument arg1 controls the size of the filter. If arg1 is an integer N, a N by N filter is created. If it is a two-vector with elements N and M, the resulting filter will be N by M. By default a 3 by 3 filter is created.

"disk"

Circular averaging filter. The optional argument arg1 controls the radius of the filter. If arg1 is an integer N, a 2 N + 1 filter is created. By default a radius of 5 is used.

"gaussian"

Gaussian filter. The optional argument arg1 controls the size of the filter. If arg1 is an integer N, a N by N filter is created. If it is a two-vector with elements N and M, the resulting filter will be N by M. By default a 3 by 3 filter is created. The optional argument arg2 sets spread of the filter. By default a spread of 0.5 is used.

"log"

Laplacian of Gaussian. The optional argument arg1 controls the size of the filter. If arg1 is an integer N, a N by N filter is created. If it is a two-vector with elements N and M, the resulting filter will be N by M. By default a 5 by 5 filter is created. The optional argument arg2 sets spread of the filter. By default a spread of 0.5 is used.

"laplacian"

3x3 approximation of the laplacian. The filter is approximated as

 (4/(alpha+1))*[alpha/4,     (1-alpha)/4, alpha/4; ...
                (1-alpha)/4, -1,          (1-alpha)/4;  ...
                alpha/4,     (1-alpha)/4, alpha/4];
 

where alpha is a number between 0 and 1. This number can be controlled via the optional input argument arg1. By default it is 0.2.

"unsharp"

Sharpening filter. The following filter is returned

 (1/(alpha+1))*[-alpha,   alpha-1, -alpha; ...
                 alpha-1, alpha+5,  alpha-1; ...
                -alpha,   alpha-1, -alpha];
 

where alpha is a number between 0 and 1. This number can be controlled via the optional input argument arg1. By default it is 0.2.

"motion"

Moion blur filter of width 1 pixel. The optional input argument arg1 controls the length of the filter, which by default is 9. The argument arg2 controls the angle of the filter, which by default is 0 degrees.

"sobel"

Horizontal Sobel edge filter. The following filter is returned

 [ 1,  2,  1;
   0,  0,  0;
  -1, -2, -1 ]
 
"prewitt"

Horizontal Prewitt edge filter. The following filter is returned

 [ 1,  1,  1;
   0,  0,  0;
  -1, -1, -1 ]
 
"kirsch"

Horizontal Kirsch edge filter. The following filter is returned

 [ 3,  3,  3;
   3,  0,  3;
  -5, -5, -5 ]
 

Package: image