MATLAB: Removing objects which have area greater and lesser than some threshold areas and extracting only the objects which have the area in between

Image Processing Toolboxremoving small and larger objects at a time?

Hi, I am doing a project on nighttime vehicle detection. I have extracted bright objects from the input traffic image.I have to remove smaller objects(noise) and larger objects(reflections) when compared to vehicle headlight objects. I have removed small objects using "sterl" function. How can i remove larger objects? Please help me in extracting based on the area of these objects. I have to extract only the in between area objects.

Thank you sir.

Best Answer

Given some image, for example (just to make a random image):

I = conv2(randn(500),ones(10)) > 10;
imshow(I);

To keep only objects between, say, 30 pixels and 50 pixels in area, you can use the BWAREAOPEN command, like this:

LB = 30;
UB = 50;
Iout = xor(bwareaopen(I,LB),  bwareaopen(I,UB));
figure, imshow(Iout);

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MATLAB: How to extract objects from an image after i have measured properties through regionprops

See my image segmentation tutorial - it goes over all of that. http://www.mathworks.com/matlabcentral/fileexchange/25157-image-segmentation-tutorial

Here's the relevant snippet. Change the filter parameters to be eccentricity and aspect ratio and you're all set.

% Now I'll demonstrate how to select certain blobs based using the ismember() function.
% Let's say that we wanted to find only those blobs
% with an intensity between 150 and 220 and an area less than 2000 pixels.
% This would give us the three brightest dimes (the smaller coin type).
allBlobIntensities = [blobMeasurements.MeanIntensity];
allBlobAreas = [blobMeasurements.Area];
% Get a list of the blobs that meet our criteria and we need to keep.
% These will be logical indices - lists of true or false depending on whether the feature meets the criteria or not.
% for example [1, 0, 0, 1, 1, 0, 1, .....].  Elements 1, 4, 5, 7, ... are true, others are false.
allowableIntensityIndexes = (allBlobIntensities > 150) & (allBlobIntensities < 220);
allowableAreaIndexes = allBlobAreas < 2000; % Take the small objects.
% Now let's get actual indexes, rather than logical indexes, of the  features that meet the criteria.
% for example [1, 4, 5, 7, .....] to continue using the example from above.
keeperIndexes = find(allowableIntensityIndexes & allowableAreaIndexes);
% Extract only those blobs that meet our criteria, and
% eliminate those blobs that don't meet our criteria.
% Note how we use ismember() to do this.  Result will be an image - the same as labeledImage but with only the blobs listed in keeperIndexes in it.
keeperBlobsImage = ismember(labeledImage, keeperIndexes);
% Re-label with only the keeper blobs kept.
labeledDimeImage = bwlabel(keeperBlobsImage, 8);     % Label each blob so we can make measurements of it
% Now we're done.  We have a labeled image of blobs that meet our specified criteria.

MATLAB: How can i separate all the connected regions in a binary image and display them individually.

Use bwlabel() and ismember

[labeledImage, numRegions] = bwlabel(binaryImage);
props = regionprops(labeledImage, 'Area')
% Compute all the areas.
allAreas = [props.Area]
% Display each blob in its own figure.
for k = 1 : numRegions
    thisRegion = ismember(labeledImage, k);
    figure;
    imshow(thisRegion);
    drawnow;
end

Best Answer

Related Solutions

MATLAB: How to extract objects from an image after i have measured properties through regionprops

MATLAB: How can i separate all the connected regions in a binary image and display them individually.

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