std2 ROI

Hi,

I am looking to calculate the standard deviation of intensity values of a grayscale image.

I do not want to calculate the standard deviation of the entire image, but just a ROI.

I can create a binary mask, but can not see a way of using this to extract the ROI statistics.

Any help would be greatly appreciated.

Cheers,

Joe

Answer 1

[Gareth Thomas]

Hi Joe,

Maybe I miss understood what you were aiming for but try logical indexing.

img = imread('pout.tif');
h_im = imshow(img);
e = imellipse(gca,[55 10 120 120]);
BW = createMask(e,h_im);
imshow(BW)
std2(img)
std2(img(BW))

Does this give you what you were looking for?

The idea here is simple. std2(A) gives the same as as std(A(:))

But the important thing is if you only want part of A, use the logical indexing to get those numbers.

Simple example:

a = [1 2 3 4; 2 3 4 5; 2 3 4 4; 4 4 1 2]
BW=a>=3
a(BW)
std2(a(BW))

Hope this helps.

[Joe]

std2(image(binary_mask)) gives me what I'm looking for.

Thanks for the help.

Joe

Answer 2

[David Young]

std(Image(logical(binary_mask)))