ZScaleInterval

class astropy.visualization.ZScaleInterval(n_samples=1000, contrast=0.25, max_reject=0.5, min_npixels=5, krej=2.5, max_iterations=5)

Bases: BaseInterval

Interval based on IRAF’s zscale.

Original implementation: spacetelescope/stsci.numdisplay

Licensed under a 3-clause BSD style license (see AURA_LICENSE.rst).

Parameters:

n_samplesint, optional

The number of points in the array to sample for determining scaling factors. Defaults to 1000.

Changed in version 7.0: nsamples parameter is removed.

contrastfloat, optional

The scaling factor (between 0 and 1) for determining the minimum and maximum value. Larger values decrease the difference between the minimum and maximum values used for display. Defaults to 0.25.

max_rejectfloat, optional

If more than max_reject * npixels pixels are rejected, then the returned values are the minimum and maximum of the data. Defaults to 0.5.

min_npixelsint, optional

If there are less than min_npixels pixels remaining after the pixel rejection, then the returned values are the minimum and maximum of the data. Defaults to 5.

krejfloat, optional

The number of sigma used for the rejection. Defaults to 2.5.

max_iterationsint, optional

The maximum number of iterations for the rejection. Defaults to 5.

Methods Summary

__call__(values[, clip, out])	Transform values using this interval.
get_limits(values)	Return the minimum and maximum value in the interval based on the values provided.

Methods Documentation

__call__(values, clip=True, out=None)

Transform values using this interval.

The vmin and vmax values are determined by the get_limits method.

The following transformation is then applied to the values:

\[{\rm result} = \frac{{\rm values} - v_{\rm min}} {v_{\rm max} - v_{\rm min}}\]

If clip is True (default), the result is then clipped to the [0:1] range.

Parameters:

valuesarray_like

The input values.

clipbool, optional

If True (default), values outside the [0:1] range are clipped to the [0:1] range.

outndarray, optional

If specified, the output values will be placed in this array (typically used for in-place calculations).

Returns:

resultndarray

The transformed values.

get_limits(values)

Return the minimum and maximum value in the interval based on the values provided.

Parameters:

valuesndarray

The image values.

Returns:

vmin, vmaxfloat

The mininium and maximum image value in the interval.