matlab improfile用法,MATLAB图像处理基本命令2

32.freqspace

附录 MATLAB图像处理命令 335

功能:确定二维频率响应的频率空间.

语法:

[f1,f2] = freqspace(n)

[f1,f2] = freqspace([m n])

[x1,y1] = freqspace(...,'meshgrid')

f = freqspace(N)

f = freqspace(N,'whole')

相关命令:fsamp2, fwind1, fwind2

33.freqz2

功能:计算二维频率响应.

语法:

[H,f1,f2] = freqz2(h,n1,n2)

[H,f1,f2] = freqz2(h,[n2 n1])

[H,f1,f2] = freqz2(h,f1,f2)

[H,f1,f2] = freqz2(h)

[...] = freqz2(h,...,[dx dy])

[...] = freqz2(h,...,dx)

freqz2(...)

举例

Hd = zeros(16,16);

Hd(5:12,5:12) = 1;

Hd(7:10,7:10) = 0;

h = fwind1(Hd,bartlett(16));

colormap(jet(64))

freqz2(h,[32 32]); axis ([-1 1 -1 1 0 1])

34.fsamp2

MATLAB高级应用——图形及影像处理 336

功能:用频率采样法设计二维FIR过滤器.

语法:

h = fsamp2(Hd)

h = fsamp2(f1,f2,Hd,[m n])

举例

[f1,f2] = freqspace(21,'meshgrid');

Hd = ones(21);

r = sqrt(f1.^2 + f2.^2);

Hd((r0.5)) = 0;

colormap(jet(64))

mesh(f1,f2,Hd)

相关命令:conv2, filter2, freqspace, ftrans2, fwind1, fwind2

35.fspecial

功能:创建预定义过滤器.

语法:

h = fspecial(type)

h = fspecial(type,parameters)

举例

I = imread('saturn.tif');

h = fspecial('unsharp',0.5);

I2 = filter2(h,I)/255;

imshow(I)

figure, imshow(I2)

相关命令:conv2, edge, filter2, fsamp2, fwind1, fwind2

36.ftrans2

功能:通过频率转换设计二维FIR过滤器.

语法:

附录 MATLAB图像处理命令 337

h = ftrans2(b,t)

h = ftrans2(b)

举例

colormap(jet(64))

b = remez(10,[0 0.05 0.15 0.55 0.65 1],[0 0 1 1 0 0]);

[H,w] = freqz(b,1,128,'whole');

plot(w/pi-1,fftshift(abs(H)))

相关命令:conv2, filter2, fsamp2, fwind1, fwind2

37.fwind1

功能:用一维窗口方法设计二维FIR过滤器.

语法:

h = fwind1(Hd,win)

h = fwind1(Hd,win1,win2)

h = fwind1(f1,f2,Hd,...)

举例

[f1,f2] = freqspace(21,'meshgrid');

Hd = ones(21);

r = sqrt(f1.^2 + f2.^2);

Hd((r0.5)) = 0;

colormap(jet(64))

mesh(f1,f2,Hd)

相关命令:conv2, filter2, fsamp2, freqspace, ftrans2, fwind2

38.fwind2

功能:用二维窗口方法设计二维FIR过滤器.

语法:

h = fwind2(Hd,win)

h = fwind2(f1,f2,Hd,win)

举例

[f1,f2] = freqspace(21,'meshgrid');

Hd = ones(21);

r = sqrt(f1.^2 + f2.^2);

Hd((r0.5)) = 0;

colormap(jet(64))

mesh(f1,f2,Hd)

MATLAB高级应用——图形及影像处理 338

相关命令:conv2, filter2, fsamp2, freqspace, ftrans2, fwind1

39.getimage

功能:从坐标轴取得图像数据.

语法:

A = getimage(h)

[x,y,A] = getimage(h)

[...,A,flag] = getimage(h)

[...] = getimage