fspecial函數用于建立預定義的濾波算子，其文法格式為：
h =
fspecial(type)
h =
fspecial(type，para)其中type指定算子的類型，para指定相應的參數；
type的類型有：
1、'average'
averaging filter為均值濾波，參數為hsize代表模闆尺寸，預設值為【3，3】。
H =
FSPECIAL('average',HSIZE) returns an averaging filter H of
size
HSIZE. HSIZE can be a vector specifying the number of rows and
columns in
H or a scalar, in which case H is a square matrix.
The
default HSIZE is [3 3].
2、'disk'
circular averaging filter
為圓形區域均值濾波，參數為radius代表區域半徑，預設值為5.
H =
FSPECIAL('disk',RADIUS) returns a circular averaging
filter
(pillbox) within the square matrix of side
2*RADIUS+1.
The default RADIUS is 5.
3、'gaussian'
Gaussian lowpass filter
為高斯低通濾波，有兩個參數，hsize表示模闆尺寸，預設值為【3
3】，sigma為濾波器的标準值，機關為像素，預設值為0.5.
H =
FSPECIAL('gaussian',HSIZE,SIGMA) returns a
rotationally
symmetric Gaussian lowpass filter
of size HSIZE with standard
deviation SIGMA (positive). HSIZE can be a vector specifying
the
number of rows and columns in H or a scalar, in which case H is
a
square matrix.
The default HSIZE is [3 3], the default SIGMA is
0.5.
4、'laplacian' filter approximating the 2-D
Laplacian operator
為拉普拉斯算子，參數alpha用于控制算子形狀，取值範圍為【0，1】，預設值為0.2.
H = FSPECIAL('laplacian',ALPHA) returns a 3-by-3
filter
approximating the shape of the two-dimensional
Laplacian
operator. The parameter ALPHA controls the shape of
the
Laplacian and must be in the range 0.0 to 1.0.
The default ALPHA is 0.2.
5、'log'
Laplacian of Gaussian filter
為拉普拉斯高斯算子，有兩個參數，hsize表示模闆尺寸，預設值為【3
3】，sigma為濾波器的标準差，機關為像素，預設值為0.5.
H =
FSPECIAL('log',HSIZE,SIGMA) returns a rotationally
symmetric
Laplacian of Gaussian filter of size HSIZE with standard
deviation
SIGMA (positive). HSIZE can be a vector specifying the number of
rows
and columns in H or a scalar, in which case H is a square
matrix.
The default HSIZE is [5 5], the default SIGMA is
0.5.
6、'motion'
motion filter
為運動模糊算子，有兩個參數，表示攝像物體逆時針方向以theta角度運動了len個像素，len的預設值為9，theta的預設值為0；
H =
FSPECIAL('motion',LEN,THETA) returns a filter to approximate,
once
convolved with an image, the linear motion of a camera by LEN
pixels,
with an angle of THETA degrees in a counter-clockwise direction.
The
filter becomes a vector for horizontal and vertical
motions.
The
default LEN is 9, the default THETA is 0, which corresponds to
a
horizontal motion of 9 pixels.
7、'prewitt'
Prewitt horizontal edge-emphasizing filter
用于邊緣增強，大小為【3
3】，無參數
H =
FSPECIAL('prewitt') returns 3-by-3 filter that
emphasizes
horizontal edges by approximating a vertical gradient. If you need
to
emphasize vertical edges, transpose the filter H:
H'.
[1 1 1;0 0 0;-1 -1 -1].
8、'sobel'
Sobel horizontal edge-emphasizing filter
用于邊緣提取，無參數
H =
FSPECIAL('sobel') returns 3-by-3 filter that
emphasizes
horizontal edges utilizing the smoothing effect by approximating
a
vertical gradient. If you need to emphasize vertical edges,
transpose
the filter H: H'.
[1 2 1;0 0 0;-1 -2 -1].
9、'unsharp'
unsharp contrast enhancement filter
為對比度增強濾波器。參數alpha用于控制濾波器的形狀，範圍為【0，1】，預設值為0.2.
H =
FSPECIAL('unsharp',ALPHA) returns a 3-by-3 unsharp
contrast
enhancement filter. FSPECIAL creates the unsharp filter from
the
negative of the Laplacian filter with parameter ALPHA. ALPHA
controls
the shape of the Laplacian and must be in the range 0.0 to
1.0.
The default ALPHA is 0.2.