graythresh() - Image Processing

level = graythresh(I) computes
a global threshold (level) that can be used to
convert an intensity image to a binary image with im2bw. level is
a normalized intensity value that lies in the range [0, 1].The graythresh function uses Otsu's method,
which chooses the threshold to minimize the intraclass variance of
the black and white pixels.Multidimensional arrays are converted automatically to 2-D arrays
using reshape. The graythresh function
ignores any nonzero imaginary part of I.[level EM] = graythresh(I) returns
the effectiveness metric, EM, as the second output
argument. The effectiveness metric is a value in the range [0 1] that
indicates the effectiveness of the thresholding of the input image.
The lower bound is attainable only by images having a single gray
level, and the upper bound is attainable only by two-valued images.

Syntax

level = graythresh(I)[level EM] = graythresh(I)

Example

I = imread('coins.png');
level = graythresh(I);
BW = im2bw(I,level);
imshow(BW)

Output / Return Value

Limitations

Alternatives / See Also

Reference