in order to extract largest size object(out of many) from an image, i used the following code but i am getting some errors please tell me where i did mistake.
I=imread('361.jpg');
I2=im2bw(I);
cc=bwconncomp(I2);
numPixels=cellfun(@numel,cc.PixelIdList);
[biggestSize,idx]=max(numPixels);
I2=false(size(I2));
I2(cc.PixelIdList{idx})=true;
i am unabe to understand the use of cellinfo() and @numel argument please explain some one. my assumption is that largest area object has maximum no.of pixels.
try I=imread('361.jpeg'); then imresize and save to other variable, would do. Your image may be in jpeg format
Will try , Attached is the snapshot of error free code and workspace for variable list
1. cc is a struct value returnted by the bwconncomp() , with 4 fields viz connectivity , size , NumObjects and PixelIdxList
2. numpixels is the variable (row vector) returned by cellfun() which takes the # of elements (@numel) and the PixelIdxList (member data , accessed thru cc.PixelIdxList)
3. max returns the maximum value from the row vector
4 And you make false all of I2 and true at those locations !!!!
Thank you very much all, i found it this typo error later i posted. but conncomp() function not giving my desired output. if back ground object is even slightly connected, then whole region is extracting, how to overcome this problem. here i am attaching both input image and the output of the above code.
my desired output should only contain bus object(largest object)
i think conncomp() works in my case if all objects are well separated.
CODE: with conncomp()
I=imread('361.jpg');
I2=im2bw(I);
cc=bwconncomp(I2);
numPix=cellfun(@numel,cc.PixelIdxList);
[BigSz,idx]=max(numPix);
%I2=false(size(I2));
%I2(cc.PixelIdxList{idx})=true;
[Row,Col]=find(cc.PixelIdxList{idx});
TT=digraph(Row,Col);
plot(TT);
bin=conncomp(TT);
concommp works with a graph , so I have used digraph you can use graph too.
find will return the coordinates , bin has the coordinates (as double) . If you want it as (x,y) the you should use mod(rowSize) and colSize for them to be in the same coordinates as the image .
Thank you Aparna Murthy,
I tried the code you have given, but i am getting error saying "Undefined function 'digraph' for input arguments of type 'double'. " . i am beginner to MATLAB, will this code gives me the bus object alone as output for the image i included. my intention is once i get the bigger object extracted, then i need to store the shape of that object as a feature. if you know how to do that, can you please guide me.
CODE:
I=imread('361.jpg');
I2=rgb2gray(I);
I22=edge(I2,'Prewitt');
se = offsetstrel('ball',3,3);
EI = imerode(I2,se);
Fifty_pts = detectHarrisFeatures(I22, 'MinQuality', 0.55);
Fifty_addr=Fifty_pts.Location;
[IndxF,CnF]=kmeans(Fifty_addr,2);
[RowF, ColF]=size(Fifty_addr);
x1=CnF(1,:);
x2=CnF(2,:);
TmpPts= Fifty_addr;
for i=1: RowF
if ((TmpPts(i,1) > x1(:,1)) | TmpPts(i,1) < x1(:,1)) & ((TmpPts(i,2) < x2(:,2)) | TmpPts(i,2) < x2(:,2))
TmpPts(i,:)=0.0;
end
end
TmpP=TmpPts(1:37,:);
TmpGrp=nonzeros(TmpP);
Count2=nnz(TmpGrp);
TTlCnt2=Count2/2;
TmpP=reshape(TmpGrp,[TTlCnt2,2]);
xmin=min(TmpP(:,1));
ymin=min(TmpP(:,2));
xmax=max(TmpP(:,1));
ymax=max(TmpP(:,2));
Width=ymax-ymin;
Len=xmax-xmin;
figure ; imshow(I) ; hold on
plot(TmpP(:,1),TmpP(:,2),'g*');
hold off
Bus=imcrop(I,[xmin,ymin,Len,Width]);
figure ; imshow(Bus)
NOTE: I have done some handpicking for the coordinates , they are fractional .
You have to do some reading on corner detection using Harrisdetector()
This is in 2016 version of MATLAB. Older hasn't got the Harrisdetector function but has a corner( ) . You can replace it.
To understand the code do debug option and step-by-step look at the variables in the workspace.
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