estimate_noise_sigma

Note

This page is a reference documentation. It only explains the function signature, and not how to use it. Please refer to the Habitat Guide and Python API guide (v2.0) for usage.

estimate_noise_sigma(array: ndarray, mask: ndarray | None = None, method: str = 'chang') → float[source]

Estimate the Gaussian noise level of an image.

Parameters:

array – Image voxel array in (z, y, x) order.
mask – Optional ROI selector; only used by method="roi_std".
method – "chang" – wavelet estimator (median absolute coefficient of the finest high-high subband of a coif1 transform, divided by 0.6754, the normal-consistency constant), applied on the last two axes (in-plane for axial acquisitions). This is the estimator MIRP uses when no noise level is given. "roi_std" – standard deviation of the intensities inside mask (or of the whole array when no mask is given), the alternative named in the paper.

Returns:

The estimated noise standard deviation in intensity units; 0.0 for a constant image.

Raises:

ValueError – For an unknown method, arrays with fewer than two axes (chang), or an empty roi_std mask.
ImportError – If method="chang" and PyWavelets is not installed.