lsst.ip.isr.linearize.LinearizeLookupTable Class Reference

Inheritance diagram for lsst.ip.isr.linearize.LinearizeLookupTable:

Public Member Functions
def	__call__ (self, image, **kwargs)

Static Public Attributes
string	LinearityType = "LookupTable"

Detailed Description

Correct non-linearity with a persisted lookup table.

The lookup table consists of entries such that given
"coefficients" c0, c1:

for each i,j of image:
    rowInd = int(c0)
    colInd = int(c1 + uncorrImage[i,j])
    corrImage[i,j] = uncorrImage[i,j] + table[rowInd, colInd]

- c0: row index; used to identify which row of the table to use
        (typically one per amplifier, though one can have multiple
        amplifiers use the same table)
- c1: column index offset; added to the uncorrected image value
        before truncation; this supports tables that can handle
        negative image values; also, if the c1 ends with .5 then
        the nearest index is used instead of truncating to the
        next smaller index

Definition at line 520 of file linearize.py.

Member Function Documentation

__call__()

def lsst.ip.isr.linearize.LinearizeLookupTable.__call__	(		self,
			image,
		**	kwargs
	)

Correct for non-linearity.

Parameters
----------
image : `lsst.afw.image.Image`
    Image to be corrected
kwargs : `dict`
    Dictionary of parameter keywords:
    ``"coeffs"``
        Columnation vector (`list` or `numpy.array`).
    ``"table"``
        Lookup table data (`numpy.array`).
    ``"log"``
        Logger to handle messages (`lsst.log.Log`).

Returns
-------
output : `tuple` [`bool`, `int`]
    If true, a correction was applied successfully.  The
    integer indicates the number of pixels that were
    uncorrectable by being out of range.

Raises
------
RuntimeError:
    Raised if the requested row index is out of the table
    bounds.

Reimplemented from lsst.ip.isr.linearize.LinearizeBase.

Definition at line 542 of file linearize.py.

    def __call__(self, image, **kwargs):
        """Correct for non-linearity.
 
        Parameters
        ----------
        image : `lsst.afw.image.Image`
            Image to be corrected
        kwargs : `dict`
            Dictionary of parameter keywords:
            ``"coeffs"``
                Columnation vector (`list` or `numpy.array`).
            ``"table"``
                Lookup table data (`numpy.array`).
            ``"log"``
                Logger to handle messages (`lsst.log.Log`).
 
        Returns
        -------
        output : `tuple` [`bool`, `int`]
            If true, a correction was applied successfully.  The
            integer indicates the number of pixels that were
            uncorrectable by being out of range.
 
        Raises
        ------
        RuntimeError:
            Raised if the requested row index is out of the table
            bounds.
        """
        numOutOfRange = 0
 
        rowInd, colIndOffset = kwargs['coeffs'][0:2]
        table = kwargs['table']
        log = kwargs['log']
 
        numTableRows = table.shape[0]
        rowInd = int(rowInd)
        if rowInd < 0 or rowInd > numTableRows:
            raise RuntimeError("LinearizeLookupTable rowInd=%s not in range[0, %s)" %
                               (rowInd, numTableRows))
        tableRow = np.array(table[rowInd, :], dtype=image.getArray().dtype)
 
        numOutOfRange += applyLookupTable(image, tableRow, colIndOffset)
 
        if numOutOfRange > 0 and log is not None:
            log.warn("%s pixels were out of range of the linearization table",
                     numOutOfRange)
        if numOutOfRange < image.getArray().size:
            return True, numOutOfRange
        else:
            return False, numOutOfRange
 
 

Member Data Documentation

LinearityType

string lsst.ip.isr.linearize.LinearizeLookupTable.LinearityType = "LookupTable"

static

Definition at line 540 of file linearize.py.

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The documentation for this class was generated from the following file:

• /j/snowflake/release/lsstsw/stack/0.4.3/Linux64/ip_isr/21.0.0-11-g2b59f77+a9c1acf22d/python/lsst/ip/isr/linearize.py