.. _calwebb_image3:

calwebb_image3: Stage 3 Imaging Processing
==========================================

:Class: `jwst.pipeline.Image3Pipeline`
:Alias: calwebb_image3

Stage 3 processing for direct-imaging observations is intended for combining the 
calibrated data from multiple exposures (e.g. a dither or mosaic pattern) into a
single rectified (distortion corrected) product.
Before being combined, the exposures receive additional corrections for the
purpose of astrometric alignment, background matching, and outlier rejection.
The steps applied by the ``calwebb_image3`` pipeline are shown below.
This pipeline is intended for non-TSO imaging only. TSO imaging data should be
processed using the :ref:`calwebb_tso3 <calwebb_tso3>` pipeline.

+--------------------------------------------------+
| calwebb_image3                                   |
+==================================================+
| :ref:`assign_mtwcs <assign_mtwcs_step>`          |
+--------------------------------------------------+
| :ref:`tweakreg <tweakreg_step>`                  |
+--------------------------------------------------+
| :ref:`skymatch <skymatch_step>`                  |
+--------------------------------------------------+
| :ref:`outlier_detection <outlier_detection_step>`|
+--------------------------------------------------+
| :ref:`resample <resample_step>`                  |
+--------------------------------------------------+
| :ref:`source_catalog <source_catalog_step>`      |
+--------------------------------------------------+

Arguments
---------

``--in_memory``
  Boolean governing whether to load all models in the input association to memory at once (faster) 
  or to save to temporary files when not in use (slower, less memory usage). Default is True.

Inputs
------

2D calibrated images
^^^^^^^^^^^^^^^^^^^^

:Data model: `~jwst.datamodels.ImageModel`
:File suffix: _cal

The inputs to the ``calwebb_image3`` pipeline are one or more
:ref:`calwebb_image2 <calwebb_image2>`
calibrated ("_cal") image products. In order to process and combine multiple
images, an ASN file must be used as input, listing the exposures to be
processed. It is also possible use a single "_cal" file as input to
``calwebb_image3``, in which case only the :ref:`resample <resample_step>` and
:ref:`source_catalog <source_catalog_step>` steps will be applied.

Outputs
-------

CR-flagged exposures
^^^^^^^^^^^^^^^^^^^^

:Data model: `~jwst.datamodels.ImageModel`
:File suffix: _crf

If the :ref:`outlier_detection <outlier_detection_step>` step is applied, a new version
of each input calibrated exposure is created, in which the DQ array has been updated to
flag pixels detected as outliers. These files use the "_crf" (CR-Flagged)
product type suffix and also includes the association candidate ID as a
new field in the original product root name, e.g.
"jw96090001001_03101_00001_nrca2_o001_crf.fits."

Resampled and combined 2D image
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

:Data model: `~jwst.datamodels.ImageModel`
:File suffix: _i2d

A resampled 2D image product of type "_i2d" is created containing the
combined, rectified association of exposures, which is the direct output of
the :ref:`resample <resample_step>` step.

Source catalog
^^^^^^^^^^^^^^

:Data model: N/A
:File suffix: _cat

The source catalog produced by the :ref:`source_catalog <source_catalog_step>` step
from the "_i2d" product is saved as an ASCII file in ``ecsv`` format, with a product type
of "_cat."

Segmentation map
^^^^^^^^^^^^^^^^

:Data model: `~jwst.datamodels.ImageModel`
:File suffix: _segm

A 2D image segmentation map produced by the :ref:`source_catalog <source_catalog_step>`
step from the "_i2d" product, saved as a FITS file with a single image extension and
a product type suffix of "_segm."