class jwst.resample.ResampleStep(name=None, parent=None, config_file=None, _validate_kwds=True, **kws)[source]

Bases: jwst.stpipe.core.JwstStep

Resample input data onto a regular grid using the drizzle algorithm.


input (DataModel or Association) – Single filename for either a single image or an association table.

Create a Step instance.

  • name (str, optional) – The name of the Step instance. Used in logging messages and in cache filenames. If not provided, one will be generated based on the class name.

  • parent (Step instance, optional) – The parent step of this step. Used to determine a fully-qualified name for this step, and to determine the mode in which to run this step.

  • config_file (str path, optional) – The path to the config file that this step was initialized with. Use to determine relative path names of other config files.

  • **kws (dict) – Additional parameters to set. These will be set as member variables on the new Step instance.

Attributes Summary



Methods Summary

get_drizpars(ref_filename, input_models)

Extract drizzle parameters from reference file.


This is where real work happens.


Update pixel scale keywords

Attributes Documentation

reference_file_types = ['drizpars']
spec = "\n        pixfrac = float(default=1.0)\n        kernel = string(default='square')\n        fillval = string(default='INDEF')\n        weight_type = option('ivm', 'exptime', default='ivm')\n        pixel_scale_ratio = float(default=1.0) # Ratio of input to output pixel scale\n        single = boolean(default=False)\n        blendheaders = boolean(default=True)\n        allowed_memory = float(default=None)  # Fraction of memory to use for the combined image.\n    "

Methods Documentation

get_drizpars(ref_filename, input_models)[source]

Extract drizzle parameters from reference file.

This method extracts parameters from the drizpars reference file and uses those to set defaults on the following ResampleStep configuration parameters:

pixfrac = float(default=None) kernel = string(default=None) fillval = string(default=None)

Once the defaults are set from the reference file, if the user has used a resample.cfg file or run ResampleStep using command line args, then these will overwerite the defaults pulled from the reference file.


This is where real work happens. Every Step subclass has to override this method. The default behaviour is to raise a NotImplementedError exception.


Update pixel scale keywords