Total Length of an image

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SANDRA COSTA 2020-2-27

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https://ww2.mathworks.cn/matlabcentral/answers/507884-total-length-of-an-image

评论： Image Analyst 2020-2-28

Hello,

Is it possible to upload an image to Matlab and calculate the total length and area?

Thank you

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Adam 2020-2-27

编辑：Adam 2020-2-27

在 MATLAB Online 中打开

How do you define the 'length' of an image? Matlab defines it as the longest dimension of an array. If that is what you want then

doc length

gives you that.

When you load an image you get a 2d array so

doc size

will give you its size. Area is trivially calculated from that if all you mean is how many pixels does it have. If you mean the area of some object in the picture that is a whole different question!

SANDRA COSTA 2020-2-27

I'm taking pictures of corals so I wanted to see if I could use matlab to measure the total length of the coral in the picture and the area.

The picture has around 5000x3000 pixels.

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Answer 1

Image Analyst 2020-2-27

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https://ww2.mathworks.cn/matlabcentral/answers/507884-total-length-of-an-image#answer_417605

You'd have to do image analysis. This includes image segmentation to get a binary map of the coral alone, then you can either take the area fraction, or skeletonize it with bwskel() and then sum the image . But I'm sure the image segmentation is probably the hardest part, but you chose not to share any images so I'm not sure how tough that would be.

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SANDRA COSTA 2020-2-27

Thank you so much.

I was able to get the threshold, but not sure on how to get the total length and area with this.

I have uploaded the image, this is what I've got so far.

Image Analyst 2020-2-28

在 MATLAB Online 中打开

I'm sure by now you've tried what I suggested and have it solved already so go ahead and post your image and code. You probably got something like

binaryImage = imbinarize(grayImage);
area = sum(binaryImage(:))
% If binaryImage doesn't have the object as white on a black background, then do this
% binaryImage = ~imbinarize(grayImage);
skelImage = bwmorph(grayImage, 'skel', inf);
totalLength = sum(skelImage(:))