how can find size of this objects in a binary image?
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hi I have a binary image and it has some objects...how can find size of this objects??Is there any toolbox in matlab for this??
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Meshooo
il 25 Set 2014
Modificato: Meshooo
il 25 Set 2014
There are many ways to do that. One easy way is to use nnz (Number of nonzero matrix elements).
So if your image is I, then:
I = im2bw (I); %be sure that your image is binary
Total_White_Pixels = nnz(I); % total area based on number of white pixels
Hope that helps you.
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Image Analyst
il 23 Ott 2021
Modificato: Image Analyst
il 23 Ott 2021
@sylvester Fok, the units are "pixels" since nnz() gives a count of elements with non-zero values in an array. If you have the area of a pixel in real world units, like it's 5 square meters per pixel, then you can multiply by that spatial calibration factor, like I do in the attached demo.
Note that this answer just gives the area of all blobs added together, not of single blobs like I showed in my answer below. Essentially:
mask = grayImage > 128; % Create a logical binary image.
props = regionprops(mask, 'Area'); % Find areas of each blob and put into a structure.
allAreas = [props.Area]
Be sure to run my Image Segmentation Tutorial.
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Meshooo
il 25 Set 2014
Modificato: Meshooo
il 25 Set 2014
You can do it in few steps. If your input image is I then:
%Step 1: Label each object using the following code.
I = im2bw(I); % be sure your image is binary
L = bwlabel(I); % label each object
%Step 2: see the label of each object
s = regionprops(L, 'Centroid');
imshow(I)
hold on
for k = 1:numel(s)
c = s(k).Centroid;
text(c(1), c(2), sprintf('%d', k), ...
'HorizontalAlignment', 'center', ...
'VerticalAlignment', 'middle');
end
hold off
% Step 3: find the area of the object you want using its label
Obj = (L == 1) % 1 is the label number of the first object.
figure, imshow(Obj);
Area = regionprops(Obj,'Area') % the answer
Now, for example if you want to find the area of object number 3, the just change number 1 to 3.
Obj = (L == 3) where 3 is the label number of the third object.
Area is the number of pixels in the object.
Hope that will help.
Image Analyst
il 24 Set 2014
Modificato: Image Analyst
il 23 Ott 2021
Of course sara. I thought you've already run across my image segmentation tutorial by now. Run it here http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862, replacing the coin image with yours. It will tell you the areas, centroids, bounding boxes, coordinates of the perimeter, etc.
Basically, it's
mask = grayImage > 128; % Create a logical binary image.
props = regionprops(mask, 'Area'); % Find areas of each blob and put into a structure.
allAreas = [props.Area]
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