make_noise_image

photutils.datasets.make_noise_image(shape, distribution='gaussian', mean=None, stddev=None, seed=None)

Make a noise image containing Gaussian or Poisson noise.

This function simply takes random samples from a Gaussian or Poisson distribution with the given parameters. If you want to apply Poisson noise to existing sources, see the apply_poisson_noise function.

Parameters:

shape2-tuple of int

The shape of the output 2D image.

distribution{‘gaussian’, ‘poisson’}, optional

The distribution used to generate the random noise:

• 'gaussian': Gaussian distributed noise.

• 'poisson': Poisson distributed noise.

meanfloat

The mean of the random distribution. Required for both Gaussian and Poisson noise.

stddevfloat, optional

The standard deviation of the Gaussian distribution. Required for Gaussian noise and ignored for Poisson noise (the variance of the Poisson distribution is equal to its mean).

seedint, optional

A seed to initialize the numpy.random.BitGenerator. If None, then fresh, unpredictable entropy will be pulled from the OS.

Returns:

image2D ndarray

Image containing random noise. The dtype is float for Gaussian noise and int for Poisson noise.

Raises:

ValueError

If mean is None, if stddev is None for Gaussian noise, or if distribution is invalid.

See also

apply_poisson_noise

Examples

import matplotlib.pyplot as plt
from photutils.datasets import make_noise_image

# Make Gaussian and Poisson noise images
shape = (100, 100)
image1 = make_noise_image(shape, distribution='gaussian', mean=0.,
                          stddev=5.)
image2 = make_noise_image(shape, distribution='poisson', mean=5.)

# Plot the images
fig, (ax1, ax2) = plt.subplots(ncols=2, figsize=(8, 4))
ax1.imshow(image1, origin='lower')
ax1.set_title(r'Gaussian noise ($\mu=0$, $\sigma=5.$)')
ax2.imshow(image2, origin='lower')
ax2.set_title(r'Poisson noise ($\mu=5$)')

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