MATLAB: How to calculate area in a binary image

@image analystareabinary imageimage enhancementimage processingImage Processing Toolbox

I have two questions to ask:

1) How to calculate area at the white region in binary image?

2) How to convert the answer of area unit that get from matlab into cm^2 or mm^2 (SI UNIT)?

here I attach the original image and binary image (this image is marine growth on the fiberglass plate)

Best Answer

Hi Asmalina,

1) To find the area in pixel size we just need to find the number of white pixel which would be

area = bwarea(bw);%bw is your binary threshold image

The unit would be pixel

2) To find the area in real world units , you need to find out how big one pixel is in appropraite units, if you working with DICOM image refer to this answer.

Another way is we can find the percentage of white area so if you have the plate area , you can find out the actual white area then.

to find out the percentage area:

percentageWhite = nnz(bw) / numel(bw);

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MATLAB: How to convert Pixel to cm or inch (i want to know 1 pixel equal = ?? mm or = ?? cm = ?? inch)

Hello , But how can i find the real length of dicom image if that is taken from a online data source. i can not use ruler to measure its mm size? Is there any way.

MATLAB: How to calculate distance in centimeters using IMDISTLINE

Put a ruler, a tape measure, a standard sheet of paper, or anything else of known length into the scene. Then snap a picture of it and use imdistline() to find the length in pixels. For example, let's say you laid down a sheet of A4 paper and measured it's distance as 2100 pixels. Knowing that it is 21 cm long, you get a spatial calibration factor of 21/2100, which you multiply your distances in pixels by to get the distance in cm. Multiply by that calibration factor squared to convert the area in pixels to the area in square centimeters.

calibrationFactor = 21/2100;
distanceInCm = distanceInPixels * calibrationFactor;
areaInSquareCm = areaInPixels * calibrationFactor ^ 2;

It's in the FAQ.

See my demo attached below for a really nice demo.

Best Answer

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MATLAB: How to convert Pixel to cm or inch (i want to know 1 pixel equal = ?? mm or = ?? cm = ?? inch)

MATLAB: How to calculate distance in centimeters using IMDISTLINE

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