How can I count the number of pixels in an image that satisfy a certain condition?

I am doing a project based on image processing. My image is in double format. I need to count the number of pixels in an image which satisfy a condition. For example, I need to count the number of pixels whose values are greater than say 0.1... And then I need to store that number in a variable for further processing. Please help me out. Thank you.

Answer 1

[Adam]

res = nnz( im > 0.1 );