一、简介
沃尔什-哈达玛变换(Walsh-Hadmard Transform,WHT),是一种典型的非正弦函数变换,采用正交直角函数作为基函数,具有与傅里叶函数类似的性质,图像数据越是均匀分布,经过沃尔什-哈达玛变换后的数据越是集中于矩阵的边角上,因此沃尔什变换具有能量集中的性质,可以用于压缩图像信息。
Matlab中的Hadamard函数:
格式:H=hadamard( n ) ,返回一个 n * n的hadamard矩阵。
二、源代码
function varargout = hadamard_encoding(varargin)
% HADAMARD_ENCODING M-file for hadamard_encoding.fig
% HADAMARD_ENCODING, by itself, creates a new HADAMARD_ENCODING or raises the existing
% singleton*.
%
% H = HADAMARD_ENCODING returns the handle to a new HADAMARD_ENCODING or the handle to
% the existing singleton*.
%
% HADAMARD_ENCODING('CALLBACK',hObject,eventData,handles,...) calls the local
% function named CALLBACK in HADAMARD_ENCODING.M with the given input arguments.
%
% HADAMARD_ENCODING('Property','Value',...) creates a new HADAMARD_ENCODING or raises the
% existing singleton*. Starting from the left, property value pairs are
% applied to the GUI before hadamard_encoding_OpeningFunction gets called. An
% unrecognized property name or invalid value makes property application
% stop. All inputs are passed to hadamard_encoding_OpeningFcn via varargin.
%
% *See GUI Options on GUIDE's Tools menu. Choose "GUI allows only one
% instance to run (singleton)".
%
% See also: GUIDE, GUIDATA, GUIHANDLES
% Edit the above text to modify the response to help hadamard_encoding
% Last Modified by GUIDE v2.5 18-Jun-2009 20:25:20
% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name', mfilename, ...
'gui_Singleton', gui_Singleton, ...
'gui_OpeningFcn', @hadamard_encoding_OpeningFcn, ...
'gui_OutputFcn', @hadamard_encoding_OutputFcn, ...
'gui_LayoutFcn', [] , ...
'gui_Callback', []);
if nargin & isstr(varargin{1})
gui_State.gui_Callback = str2func(varargin{1});
end
if nargout
[varargout{1:nargout}] = gui_mainfcn(gui_State, varargin{:});
else
gui_mainfcn(gui_State, varargin{:});
end
% End initialization code - DO NOT EDIT
% --- Executes just before hadamard_encoding is made visible.
function hadamard_encoding_OpeningFcn(hObject, eventdata, handles, varargin)
% This function has no output args, see OutputFcn.
% hObject handle to figure
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% varargin command line arguments to hadamard_encoding (see VARARGIN)
cr = 0.5;
I = imread('lena.bmp');
axes(handles.axes1);
imshow(I);
I = double(I)/255;
t = hadamard(8);
fftcoe = blkproc(I,[8 8],'P1*x*P2',t,t);
coevar = im2col(fftcoe,[8 8],'distinct');
coe = coevar;
[y,ind] = sort(coevar);
[m,n] = size(coevar);
snum = 64-64*cr;
for i = 1:n
coe(ind(1:snum),i) = 0;
end
B2 = col2im(coe,[8 8],[512 512],'distinct');
I2 = blkproc(B2,[8,8],'P1*x*P2',t,t);
I2 = I2./(8*8);
axes(handles.axes2);
imshow(I2);
e = double(I) - double(I2);
[m,n]=size(e);
erms = sqrt(sum(e(:).^2)/(m*n));
set(handles.erms_edit,'string',erms);
set(handles.cr_edit,'string',0.5);
% Choose default command line output for hadamard_encoding
handles.output = hObject;
% Update handles structure
guidata(hObject, handles);
% UIWAIT makes hadamard_encoding wait for user response (see UIRESUME)
% uiwait(handles.figure1);
% --- Outputs from this function are returned to the command line.
function varargout = hadamard_encoding_OutputFcn(hObject, eventdata, handles)
% varargout cell array for returning output args (see VARARGOUT);
% hObject handle to figure
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Get default command line output from handles structure
varargout{1} = handles.output;
% --- Executes during object creation, after setting all properties.
function image_pop_menu_CreateFcn(hObject, eventdata, handles)
% hObject handle to image_pop_menu (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: popupmenu controls usually have a white background on Windows.
% See ISPC and COMPUTER.
if ispc
set(hObject,'BackgroundColor','white');
else
set(hObject,'BackgroundColor',get(0,'defaultUicontrolBackgroundColor'));
end
% --- Executes on selection change in image_pop_menu.
function image_pop_menu_Callback(hObject, eventdata, handles)
% hObject handle to image_pop_menu (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
val = get(hObject,'value');
str = get(hObject,'string');
cr = str2num(get(handles.cr_edit,'string'));
switch str{val}
case 'Lena'
I = imread('lena.bmp');
case 'Cameraman'
I = imread('cameraman.tif');
case 'Peppers'
I = imread('peppers.bmp');
case 'Fingerprint'
I = imread('fingerprint.jpg');
case 'Licenceplate'
I = imread('licenceplate.jpg');
case 'Cloudy'
I = imread('cloudy.tif');
end
axes(handles.axes1);
imshow(I);
I = double(I)/255;
t = hadamard(8);
fftcoe = blkproc(I,[8 8],'P1*x*P2',t,t);
coevar = im2col(fftcoe,[8 8],'distinct');
coe = coevar;
[y,ind] = sort(coevar);
[m,n] = size(coevar);
snum = 64-64*cr;
for i = 1:n
coe(ind(1:snum),i) = 0;
end
B2 = col2im(coe,[8 8],size(I),'distinct');
I2 = blkproc(B2,[8,8],'P1*x*P2',t,t);
I2 = I2./(8*8);
axes(handles.axes2);
imshow(I2);
e = double(I) - double(I2);
[m,n]=size(e);
erms = sqrt(sum(e(:).^2)/(m*n));
set(handles.erms_edit,'string',erms);
set(handles.cr_edit,'string',0.5);
% Hints: contents = get(hObject,'String') returns image_pop_menu contents as cell array
% contents{get(hObject,'Value')} returns selected item from image_pop_menu
% --- Executes during object creation, after setting all properties.
function cr_edit_CreateFcn(hObject, eventdata, handles)
% hObject handle to cr_edit (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles empty - handles not created until after all CreateFcns called
% Hint: edit controls usually have a white background on Windows.
% See ISPC and COMPUTER.
if ispc
set(hObject,'BackgroundColor','white');
else
set(hObject,'BackgroundColor',get(0,'defaultUicontrolBackgroundColor'));
end
function cr_edit_Callback(hObject, eventdata, handles)
% hObject handle to cr_edit (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'String') returns contents of cr_edit as text
% str2double(get(hObject,'String')) returns contents of cr_edit as a double
% --- Executes on button press in apply_button.
function apply_button_Callback(hObject, eventdata, handles)
% hObject handle to apply_button (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
cr = str2num(get(handles.cr_edit,'string'));
I = getimage(handles.axes1);
I = double(I)/255;
t = hadamard(8);
fftcoe = blkproc(I,[8 8],'P1*x*P2',t,t);
coevar = im2col(fftcoe,[8 8],'distinct');
coe = coevar;
[y,ind] = sort(coevar);
[m,n] = size(coevar);
snum = 64-floor(64*cr);
for i = 1:n
coe(ind(1:snum),i) = 0;
end
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