GaussianPsfFactory

class lsst.meas.algorithms.GaussianPsfFactory

Bases: lsst.pex.config.Config

Factory for simple Gaussian PSF models

Provides a high-level interface to DoubleGaussianPsf and SingleGaussianPsf by specifying Gaussian PSF model width in FWHM instead of sigma, and supporting computing kernel size as a multiple of PSF width. This makes it suitable for tasks where PSF width is not known in advance.

Attributes Summary

addWing Add a Gaussian to represent wings? (bool, default True)
defaultFwhm Default FWHM of Gaussian model of core of star (pixels) (float, default 3.0)
history
maxSize Maximum kernel size if using sizeFactor (pixels); ignored if size is not None (int, default None)
minSize Minimum kernel size if using sizeFactor (pixels); ignored if size is not None (int, default 5)
size Kernel size (width and height) (pixels); if None then sizeFactor is used (int, default None)
sizeFactor Kernel size as a factor of fwhm (dimensionless); size = sizeFactor * fwhm; ignored if size is not None (float, default 3.0)
wingAmplitude wing amplitude, as a multiple of core amplitude (dimensionless); ignored if addWing false (float, default 0.1)
wingFwhmFactor wing width, as a multiple of core width (dimensionless); ignored if addWing false (float, default 2.5)

Methods Summary

apply([fwhm]) Construct a GaussianPsf
compare(other[, shortcut, rtol, atol, output]) Compare this configuration to another Config for equality.
computeSizeAndSigma([fwhm]) Compute kernel size and star width as sigma.
formatHistory(name, **kwargs) Format a configuration field’s history to a human-readable format.
freeze() Make this config, and all subconfigs, read-only.
items() Get configurations as (field name, field value) pairs.
keys() Get field names.
load(filename[, root]) Modify this config in place by executing the Python code in a configuration file.
loadFromStream(stream[, root, filename]) Modify this Config in place by executing the Python code in the provided stream.
loadFromString(code[, root, filename]) Modify this Config in place by executing the Python code in the provided string.
makeField(doc) Make an lsst.pex.config.ConfigurableField
names() Get all the field names in the config, recursively.
save(filename[, root]) Save a Python script to the named file, which, when loaded, reproduces this config.
saveToStream(outfile[, root, skipImports]) Save a configuration file to a stream, which, when loaded, reproduces this config.
saveToString([skipImports]) Return the Python script form of this configuration as an executable string.
setDefaults() Subclass hook for computing defaults.
toDict() Make a dictionary of field names and their values.
update(**kw) Update values of fields specified by the keyword arguments.
validate() Validate the Config, raising an exception if invalid.
values() Get field values.

Attributes Documentation

addWing

Add a Gaussian to represent wings? (bool, default True)

defaultFwhm

Default FWHM of Gaussian model of core of star (pixels) (float, default 3.0)

history
maxSize

Maximum kernel size if using sizeFactor (pixels); ignored if size is not None (int, default None)

minSize

Minimum kernel size if using sizeFactor (pixels); ignored if size is not None (int, default 5)

size

Kernel size (width and height) (pixels); if None then sizeFactor is used (int, default None)

sizeFactor

Kernel size as a factor of fwhm (dimensionless); size = sizeFactor * fwhm; ignored if size is not None (float, default 3.0)

wingAmplitude

wing amplitude, as a multiple of core amplitude (dimensionless); ignored if addWing false (float, default 0.1)

wingFwhmFactor

wing width, as a multiple of core width (dimensionless); ignored if addWing false (float, default 2.5)

Methods Documentation

apply(fwhm=None)

Construct a GaussianPsf

Parameters:
fwhm : float

FWHM of core of star (pixels); if None then self.defaultFwhm is used

Returns:
DoubleGaussianPsf : lsst.meas.algorithms.DoubleGaussianPsf

Returns if self.addWing is True

SingleGaussianPsf : lsst.meas.algorithms.SingleGaussianPsf

Returns if self.addWing is False

compare(other, shortcut=True, rtol=1e-08, atol=1e-08, output=None)

Compare this configuration to another Config for equality.

Parameters:
other : lsst.pex.config.Config

Other Config object to compare against this config.

shortcut : bool, optional

If True, return as soon as an inequality is found. Default is True.

rtol : float, optional

Relative tolerance for floating point comparisons.

atol : float, optional

Absolute tolerance for floating point comparisons.

output : callable, optional

A callable that takes a string, used (possibly repeatedly) to report inequalities.

Returns:
isEqual : bool

True when the two lsst.pex.config.Config instances are equal. False if there is an inequality.

Notes

Unselected targets of RegistryField fields and unselected choices of ConfigChoiceField fields are not considered by this method.

Floating point comparisons are performed by numpy.allclose.

computeSizeAndSigma(fwhm=None)

Compute kernel size and star width as sigma. The kernel size will be odd unless minSize or maxSize is used and that value is even. Assumes a valid config.

Parameters:
fwhm : float

FWHM of core star (pixels); if None then defaultFwhm is used

Returns:
size : int

Kernel size (width == height) in pixels

sigma : float

Sigma equivalent to supplied FWHM, assuming a Gaussian (pixels)

formatHistory(name, **kwargs)

Format a configuration field’s history to a human-readable format.

Parameters:
name : str

Name of a Field in this config.

kwargs

Keyword arguments passed to lsst.pex.config.history.format.

Returns:
history : str

A string containing the formatted history.

freeze()

Make this config, and all subconfigs, read-only.

items()

Get configurations as (field name, field value) pairs.

Returns:
items : dict_items

Iterator of tuples for each configuration. Tuple items are:

  1. Field name.
  2. Field value.
keys()

Get field names.

Returns:
names : dict_keys

List of lsst.pex.config.Field names.

See also

lsst.pex.config.Config.iterkeys
load(filename, root='config')

Modify this config in place by executing the Python code in a configuration file.

Parameters:
filename : str

Name of the configuration file. A configuration file is Python module.

root : str, optional

Name of the variable in file that refers to the config being overridden.

For example, the value of root is "config" and the file contains:

config.myField = 5

Then this config’s field myField is set to 5.

loadFromStream(stream, root='config', filename=None)

Modify this Config in place by executing the Python code in the provided stream.

Parameters:
stream : file-like object, str, bytes, or compiled string

Stream containing configuration override code. If this is a code object, it should be compiled with mode="exec".

root : str, optional

Name of the variable in file that refers to the config being overridden.

For example, the value of root is "config" and the file contains:

config.myField = 5

Then this config’s field myField is set to 5.

filename : str, optional

Name of the configuration file, or None if unknown or contained in the stream. Used for error reporting.

Notes

For backwards compatibility reasons, this method accepts strings, bytes and code objects as well as file-like objects. New code should use loadFromString instead for most of these types.

loadFromString(code, root='config', filename=None)

Modify this Config in place by executing the Python code in the provided string.

Parameters:
code : str, bytes, or compiled string

Stream containing configuration override code.

root : str, optional

Name of the variable in file that refers to the config being overridden.

For example, the value of root is "config" and the file contains:

config.myField = 5

Then this config’s field myField is set to 5.

filename : str, optional

Name of the configuration file, or None if unknown or contained in the stream. Used for error reporting.

classmethod makeField(doc)

Make an lsst.pex.config.ConfigurableField

names()

Get all the field names in the config, recursively.

Returns:
names : list of str

Field names.

save(filename, root='config')

Save a Python script to the named file, which, when loaded, reproduces this config.

Parameters:
filename : str

Desination filename of this configuration.

root : str, optional

Name to use for the root config variable. The same value must be used when loading (see lsst.pex.config.Config.load).

saveToStream(outfile, root='config', skipImports=False)

Save a configuration file to a stream, which, when loaded, reproduces this config.

Parameters:
outfile : file-like object

Destination file object write the config into. Accepts strings not bytes.

root

Name to use for the root config variable. The same value must be used when loading (see lsst.pex.config.Config.load).

skipImports : bool, optional

If True then do not include import statements in output, this is to support human-oriented output from pipetask where additional clutter is not useful.

saveToString(skipImports=False)

Return the Python script form of this configuration as an executable string.

Parameters:
skipImports : bool, optional

If True then do not include import statements in output, this is to support human-oriented output from pipetask where additional clutter is not useful.

Returns:
code : str

A code string readable by loadFromString.

setDefaults()

Subclass hook for computing defaults.

Notes

Derived Config classes that must compute defaults rather than using the Field instances’s defaults should do so here. To correctly use inherited defaults, implementations of setDefaults must call their base class’s setDefaults.

toDict()

Make a dictionary of field names and their values.

Returns:
dict_ : dict

Dictionary with keys that are Field names. Values are Field values.

Notes

This method uses the toDict method of individual fields. Subclasses of Field may need to implement a toDict method for this method to work.

update(**kw)

Update values of fields specified by the keyword arguments.

Parameters:
kw

Keywords are configuration field names. Values are configuration field values.

Notes

The __at and __label keyword arguments are special internal keywords. They are used to strip out any internal steps from the history tracebacks of the config. Do not modify these keywords to subvert a Config instance’s history.

Examples

This is a config with three fields:

>>> from lsst.pex.config import Config, Field
>>> class DemoConfig(Config):
...     fieldA = Field(doc='Field A', dtype=int, default=42)
...     fieldB = Field(doc='Field B', dtype=bool, default=True)
...     fieldC = Field(doc='Field C', dtype=str, default='Hello world')
...
>>> config = DemoConfig()

These are the default values of each field:

>>> for name, value in config.iteritems():
...     print(f"{name}: {value}")
...
fieldA: 42
fieldB: True
fieldC: 'Hello world'

Using this method to update fieldA and fieldC:

>>> config.update(fieldA=13, fieldC='Updated!')

Now the values of each field are:

>>> for name, value in config.iteritems():
...     print(f"{name}: {value}")
...
fieldA: 13
fieldB: True
fieldC: 'Updated!'
validate()

Validate the Config, raising an exception if invalid.

Raises:
lsst.pex.config.FieldValidationError

Raised if verification fails.

Notes

The base class implementation performs type checks on all fields by calling their validate methods.

Complex single-field validation can be defined by deriving new Field types. For convenience, some derived lsst.pex.config.Field-types (ConfigField and ConfigChoiceField) are defined in lsst.pex.config that handle recursing into subconfigs.

Inter-field relationships should only be checked in derived Config classes after calling this method, and base validation is complete.

values()

Get field values.

Returns:
values : dict_values

Iterator of field values.