What you are saying is this:
binaryImage = bwareafilt(binaryImage, 1); % Extract largest blob only.
props = regionprops(binaryImage, 'BoundingBox');
height = props.BoundingBox(4)
This way is susceptible to little outliers, like the two you have on the top. A better way may be to either scan the blob vertically getting the height at every column and then taking the average
heights = zeros(rows, 1);
for col = 1 : columns
thisColumn = binaryImage(:, col);
if max(thisColumn) > 0 % If there are white pixels in the column
topRow = find(thisColumn, 1, 'first');
bottomRow = find(thisColumn, 1, 'last');
heights(col) = bottomRow - topRow + 1;
end
end
averageHeight = mean(heights(heights>0))
Or, get the average vertical profile and threshold it at some level
verticalProfile = sum(binaryImage, 2);
averageHeight = sum(verticalProfile > someLevel)
All 3 methods will/could give different heights. It just depends on how you want to define height. I mean, look at the bottom of your bottle - it's not flat so you don't have a perfect rectangle aligned with the edges of the image, so there are different ways to define height.
