MATLAB: How to calculate the area of certain portion of an image

Question

how to calculate the area of certain portion of an image ?

Answer 1

Call regionprops(). See my Image Segmentation Tutorial. It goes over all of that:

BlobsDemo

For example with a simple thresholding:

binaryImage = grayImage > 90;
measurements = regionprops(binaryImage, 'Area');
allAreas = [measurements.Area];