verify which one is the correct one to calculate

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bay rem 2016-2-3

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https://ww2.mathworks.cn/matlabcentral/answers/266460-verify-which-one-is-the-correct-one-to-calculate

评论： Walter Roberson 2016-2-3

i tried both of those instruction to calculate variance of each blob in one image, both leads to different results, i dont know wich one is the correct one can you please help me

for i=1: numofblobs
   croppedImage = frameRGB(bbox(i, 2):bbox(i, 2)+bbox(i, 4)-1, bbox(i, 1):bbox(i, 1)+bbox(i, 3)-1, :);
       blobVariance(i) = var(double(croppedImage(:)));
    end
OR 
for i=1: numofblobs
    blobVariance(i) = var(double(bbox(i,:)))
end

where

bbox = step(blobAnalysis, binaryimage);

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Answer 1

Walter Roberson 2016-2-3

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We would need to see the configuration of your blobanalysis to be sure, but the second code appears to be finding the variance in the coordinates of bounding boxes but the first one appears to be looking at the variance in the content of the images inside the bounding boxes

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bay rem 2016-2-3

编辑：bay rem 2016-2-3

在 MATLAB Online 中打开

thank you Here there is the configuration of blobAnalysis

blobAnalysis = vision.BlobAnalysis('BoundingBoxOutputPort', true, ...
    'AreaOutputPort', false, 'CentroidOutputPort', false, ...
    'MinimumBlobArea', 1700,'MaximumCount',2);