一、简介

投影，在立体几何中我们学到过，是空间直线在某个方向上的投影，那么图像处理中也是这种投影思想。

最简单的投影：
水平方向投影，将图像数组进行列求和；
垂直方向投影，将图像数组进行行求和；
对于二值图像或明显特征的灰度图分割前景与背景，经常用到投影法。

二、源代码

unction varargout = chongjian(varargin)
% CHONGJIAN MATLAB code for chongjian.fig
%      CHONGJIAN, by itself, creates a new CHONGJIAN or raises the existing
%      singleton*.
%
%      H = CHONGJIAN returns the handle to a new CHONGJIAN or the handle to
%      the existing singleton*.
%
%      CHONGJIAN('CALLBACK',hObject,eventData,handles,...) calls the local
%      function named CALLBACK in CHONGJIAN.M with the given input arguments.
%
%      CHONGJIAN('Property','Value',...) creates a new CHONGJIAN or raises the
%      existing singleton*.  Starting from the left, property value pairs are
%      applied to the GUI before chongjian_OpeningFcn gets called.  An
%      unrecognized property name or invalid value makes property application
%      stop.  All inputs are passed to chongjian_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 chongjian

% Last Modified by GUIDE v2.5 22-Mar-2020 18:21:37

% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name',       mfilename, ...
                   'gui_Singleton',  gui_Singleton, ...
                   'gui_OpeningFcn', @chongjian_OpeningFcn, ...
                   'gui_OutputFcn',  @chongjian_OutputFcn, ...
                   'gui_LayoutFcn',  [] , ...
                   'gui_Callback',   []);
if nargin && ischar(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 chongjian is made visible.
function chongjian_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 chongjian (see VARARGIN)
axes(handles.axes1);
imshow([255]);
axes(handles.axes2);
imshow([255]);
axes(handles.axes3);
imshow([255]);
% Choose default command line output for chongjian
handles.output = hObject;

% Update handles structure
guidata(hObject, handles);

% UIWAIT makes chongjian wait for user response (see UIRESUME)
% uiwait(handles.figure1);


% --- Outputs from this function are returned to the command line.
function varargout = chongjian_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 on button press in pushbutton1.
function pushbutton1_Callback(hObject, eventdata, handles)
global tu
axes(handles.axes1)
[filename,pathname]=uigetfile({ ...
    '*.*','All Files(*.*)';},...
    '选择文件');
%
if isequal([filename,pathname],[0,0])
    return
else
    %读取图片
    pic = fullfile(pathname,filename);
    b = imread(pic);

    imshow(b);%上面是打开图片的步骤，这一句是显示图片
    tu=b;

    title('原始图像');
    %handle.axes1=b;
end
% hObject    handle to pushbutton1 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)


% --- Executes on button press in pushbutton2.
function pushbutton2_Callback(hObject, eventdata, handles)
global tu
global tu2
P = tu;

[N,N]=size(P);


%先进行自定义radon变换------------------------------------------------------------
thm=45;                %45度时会出现最大尺寸
pre = imrotate(P,thm);
[mmax,nmax] = size(pre);
s=1;
%创建一个180*nmax的空白图片，用以存储投影后的线状图片
Final = zeros(180/s,nmax);%这里180代表180角度，每个角度投影成为一条线
t = 1;
for theta = 1:s:179
Protate = imrotate(P,theta);    %对原图旋转一个角度，求和（线积分）
Pf = sum(Protate,1);
[mreal,nreal]=size(Pf);           %计算实际尺寸
%确定起始点
if (nmax - nreal)/2-floor((nmax - nreal)/2) == 0
    From = floor((nmax - nreal)/2 + 1);%总点数为偶数时
   else
    From = floor((nmax - nreal)/2) + 1;%总点数为奇数时
    end
    %结果文本显示------------------------------------------------------------
% o=ones(500,1000);
% subplot(2,3,6);
% imshow(o,[]);
% s_title=['图像重建精度判据如下:'];
% text(0,0,s_title,'Fontsize',14);
% s=num2str(toc);
% s_one=['run time = ' s ' s;'];
% text(0,100,s_one,'FontSize',10);  
% s=num2str(evaluate_d);
% s_two=['归一化均方距离判据d=' s ';'];
% text(0,200,s_two,'Fontsize',10);
% s=num2str(evaluate_r);
% s_three=['归一化平均绝对距离判据r=' s ';'];
% text(0,300,s_three,'Fontsize',10);
% s=num2str(evaluate_e);
% s_four=['最坏情况距离判据e=' s ';'];
% text(0,400,s_four,'Fontsize',10);
% toc

% hObject    handle to pushbutton2 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)


% --- Executes on button press in pushbutton3.
function pushbutton3_Callback(hObject, eventdata, handles)
global tu2
axes(handles.axes3);
imshow(tu2);
title('投影重建后的图像');
% hObject    handle to pushbutton3 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)


% --- Executes on button press in pushbutton4.
function pushbutton4_Callback(hObject, eventdata, handles)
axes(handles.axes1);
imshow([255]);
axes(handles.axes2);
imshow([255]);
axes(handles.axes3);
imshow([255]);
% hObject    handle to pushbutton4 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

三、运行结果

四、备注

完整代码或者代写添加QQ 1564658423