Area of objects in binary image
Read a binary image and display it.
BW = imread('circles.png'); imshow(BW)
Calculate the area of objects in the image.
ans = 1.4187e+04
BW— Binary image
Binary image, specified as a 2-D numeric or logical matrix.
BW = imread('text.png'); L =
bwarea estimates the area of all of the
pixels in an image by summing the areas of each pixel in the image. The area of an
individual pixel is determined by looking at its 2-by-2 neighborhood. There are six
different patterns, each representing a different area:
Patterns with zero
on pixels (area = 0)
Patterns with one
on pixel (area = 1/4)
Patterns with two adjacent
on pixels (area = 1/2)
Patterns with two diagonal
on pixels (area = 3/4)
Patterns with three
on pixels (area = 7/8)
Patterns with all four
on pixels (area = 1)
Each pixel is part of four different 2-by-2 neighborhoods. This means, for example,
that a single
on pixel surrounded by
has a total area of 1.
 Pratt, William K., Digital Image Processing, New York, John Wiley & Sons, Inc., 1991, p. 634.