The edge detection is to detect the change of neighbor pixel from 1 to 0 or vise versa. This detection is performed with the logical operator XOR. This operator returns 1 if its two inputs are different. In this way, if there was a change between the two input pixels then the output pixel will be white, otherwise it will be black.
| e1 | e2 | s |
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 0 |
Now you must choose the correct input pixels of the XOR gate. Look at the diagram below.
To see the edges in several directions, it is important to make many operations. For a square mask of order 1, we can detect edges in four directions.
The direction is defined by the line between the two input pixels of XOR gates.
If the mask does not provide every direction, the edge risks to be mis identify.
The image must be very few parasites to not detect edge due to noise.
If one or more front is detected in a mask then the output must be equal to 1, so we must use an OR between all the outputs of XOR.
output = 1 if (n1 XOR n1')=1 OU (n2 XOR n2')=1 OU (n3 XOR n3')=1 OU (n4 XOR n4')=1, otherwise output = 0
function guifront
%translationfunction guihistogramme
clear all;
close all;
figure( 'name','majorité',...
'NumberTitle','off',...
'color',[0.3137 0.3137 0.5098]);
a(1)=axes('units','normalized',...
'position',[0.05 0.60 0.35 0.35]);
a(2)=axes('units','normalized',...
'position',[0.05 0.15 0.35 0.35]);
a(3)=axes('units','normalized',...
'position',[0.50 0.60 0.35 0.35]);
a(4)=axes('units','normalized',...
'position',[0.50 0.15 0.35 0.35]);
uicontrol( 'style','pushbutton',...
'string','load',...
'Position', [10 10 50 20],...
'callback',@loadimage);
uicontrol( 'style','pushbutton',...
'string','majorité',...
'Position', [100 10 50 20],...
'callback',@majorite);
uicontrol( 'style','pushbutton',...
'string','front',...
'Position', [400 10 50 20],...
'callback',@front);
uicontrol( 'style','popup',...
'string','ligne|colonne|croix|carre',...
'Min',0,'Max',4,...
'Position', [200 10 50 20],...
'callback',{@choix,'typemasque'});
uicontrol( 'style','popup',...
'string','1|2|3|4|5',...
'Min',0,'Max',4,...
'Position', [300 10 50 20],...
'callback',{@choix,'ordrefiltre'});
uicontrol( 'style','popup',...
'string','1|2|3|4|5',...
'Min',0,'Max',4,...
'Position', [500 10 50 20],...
'callback',{@choix,'ordrefront'});
text(1)=uicontrol( 'style','text',...
'string','ordre majorite ',...
'Position', [300 30 70 20]);
text(2)=uicontrol( 'style','text',...
'string','odre front ',...
'Position', [500 30 70 20]);
%parametre initial
setappdata(gcf,'k',8);
setappdata(gcf,'x',1);
setappdata(gcf,'img2',1);
setappdata(gcf,'typemasque',0);
setappdata(gcf,'ordrefiltre',0);
setappdata(gcf,'ordrefront',0);
function loadimage(~,~)
% appeler quand appui check box
[filename, pathname] = uigetfile({'*.jpg;*.tif;*.png;*.gif;*.bmp','All Image Files';...
'*.*','All Files' },'mytitle',...
'C:\Work\myfile.jpg')
x = imread(filename);
axes(a(1))
imshow(x)
if (length(size(x))>2)
x=mean(x,3);% on prend une seul plan image noir et blanc chaque plan sont egaux
end
x=uint8(x);
k = whos('x');
if k.class == 'uint8'
k=8;
end
% on inverse l'image les objets sont noir
img2=uint8(x);
axes(a(2))
imshow(img2)
x=x/255;
img2=img2/255;
setappdata(1,'k',k);
setappdata(1,'x',x);
setappdata(1,'img2',img2);
end
function majorite(hObj,~)
typemasque = getappdata(1,'typemasque');
ordre = getappdata(1,'ordrefiltre');
if (ordre == 0 || ordre == 1)
ordre=1;
end
img = getappdata(1,'x');
k = getappdata(1,'k');
[ligne colonne]=size(img);
img2=zeros(ligne,colonne);
for i=ordre+1:ligne-ordre%attention aux debordement
for j =ordre+1:colonne-ordre%attention aux debordement
if (typemasque==0 || typemasque==1) %ligne
for o = -ordre : 1 : ordre
img2(i,j)=img2(i,j) + img(i+o,j);
end
elseif typemasque==2
for o = -ordre : 1 : ordre
img2(i,j)=img2(i,j) + img(i,j+o);
end
elseif typemasque==3
for o = -ordre : 1 : ordre
img2(i,j)=img2(i,j) + img(i+o,j) + img(i,j+o);
end
else
for o1 = -ordre : 1 : ordre
for o2 = -ordre : 1 : ordre
img2(i,j)=img2(i,j) + img(i+o1,j+o2);
end
end
end
end
end
if (typemasque==0 || typemasque==1)
taillemasque = 1 + 2*ordre;
elseif typemasque==2
taillemasque = 1 + 2*ordre;
elseif typemasque==3
taillemasque = 1 + 4*ordre;
else
taillemasque = ((ordre*2)+1)^2;
end
seuilmajorite=ceil(taillemasque/2);
for i = 1 : ligne
for j = 1 : colonne
if (img2(i,j)>seuilmajorite)
img2(i,j)=1;
else
img2(i,j)=0;
end
end
end
setappdata(1,'img2',img2);
axes(a(2))
imshow(img2)
end
function front(hObj,~)
typemasque = getappdata(1,'typemasque');
ordre = getappdata(1,'ordrefront');
if (ordre == 0 || ordre == 1)
ordre=1;
end
x = getappdata(1,'x');
img2 = getappdata(1,'img2');
k = getappdata(1,'k');
[ligne colonne]=size(img2);
x2=zeros(ligne,colonne);
for i=ordre+1:ligne-ordre%attention aux debordement
for j =ordre+1:colonne-ordre%attention aux debordement
if (typemasque==0 || typemasque==1) %ligne
x2(i,j)=xor(x(i-ordre,j) , x(i+ordre,j));% detection horisontal
elseif typemasque==2
x2(i,j)=xor(x(i,j-ordre) , x(i,j+ordre));% detection vertical
elseif typemasque==3
x2(i,j)=xor(x(i-ordre,j) , x(i+ordre,j)) |... % detection horisontal
xor(x(i,j-ordre) , x(i,j+ordre)); % detection vertical
else
x2(i,j)=xor(x(i-ordre,j) , x(i+ordre,j)) |... % detection horisontal
xor(x(i,j-ordre) , x(i,j+ordre)) |... % detection vertical
xor(x(i-ordre,j-ordre) , x(i+ordre,j+ordre)) |... % detection diagonal decendante
xor(x(i-ordre,j+ordre) , x(i+ordre,j-ordre)); % detection diagonal montante
end
end
end
img3=zeros(ligne,colonne);
for i=ordre+1:ligne-ordre%attention aux debordement
for j =ordre+1:colonne-ordre%attention aux debordement
if (typemasque==0 || typemasque==1) %ligne
img3(i,j)=xor(img2(i-ordre,j) , img2(i+ordre,j));% detection horisontal
elseif typemasque==2
img3(i,j)=xor(img2(i,j-ordre) , img2(i,j+ordre));% detection vertical
elseif typemasque==3
img3(i,j)=xor(img2(i-ordre,j) , img2(i+ordre,j)) |... % detection horisontal
xor(img2(i,j-ordre) , img2(i,j+ordre)); % detection vertical
else
img3(i,j)=xor(img2(i-ordre,j) , img2(i+ordre,j)) |... % detection horisontal
xor(img2(i,j-ordre) , img2(i,j+ordre)) |... % detection vertical
xor(img2(i-ordre,j-ordre) , img2(i+ordre,j+ordre)) |... % detection diagonal decendante
xor(img2(i-ordre,j+ordre) , img2(i+ordre,j-ordre)); % detection diagonal montante
end
end
end
axes(a(3))
imshow(x2)
axes(a(4))
imshow(img3)
end
function choix(hObj,~,name)
% Called when user activates popup menu
val = get(hObj,'Value'); %0|1=ligne, 2=colonne, 3=croix, 4=carre
setappdata(1,name,val);
end
end
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