# Region mapping for TweakReg

This module provides functions for mapping DS9 region files given in sky coordinates to DS9 region files specified in image coordinates of multiple images using the WCS information from the images.

Authors: | Mihai Cara
License: | http://www.stsci.edu/resources/software_hardware/pyraf/LICENSE

`drizzlepac.mapreg.``MapReg`(input_reg, images, img_wcs_ext='sci', refimg='', ref_wcs_ext='sci', chip_reg='', outpath='./regions', filter='', catfname='', iteractive=False, append=False, verbose=True)

  `MapReg` provides an automated interface for converting a region file to the image coordinate system (CS) of multiple images (and their extensions) using WCS information from the image(s) header(s). This conversion does not take into account pointing errors and, therefore, an examination and adjustment (if required) of output region files is highly recommended. This task is designed to simplify the creation of the exclusions and/or inclusions region files used with `TweakReg` task for sources finding.

  Parameters: | input_reg : string or list of strings (Default = ‘’) Input region files that need to be mapped to image CS using WCS information from `images` (see below). Only region files saved in sky CS are allowed in this release. Regions specified in image-like coordinates (e.g., image, physical) will be ignored. This paramater can be provided in any of several forms: filename of a single image comma-separated list of filenames `@-file` filelist containing list of desired input region filenames The `@-file` filelist needs to be provided as an ASCII text file containing a list of filenames for all input region files with one filename on each line of the file. images : string or list of strings (Default = `*.fits`) FITS images onto which the region files `input_reg` will be mapped. These image files must contain WCS information in their headers in order to convert `input_reg` from sky coordinates to correct image coordinates. This paramater can be provided in any of several forms: filename of a single image filename of an association (ASN)table wild-card specification for files in directory (using `*`, `?` etc.) comma-separated list of filenames `@-file` filelist containing list of desired input filenames (and optional inverse variance map filenames) The `@-file` filelist needs to be provided as an ASCII text file containing a list of filenames for all input images (to which `input_reg` regions should be mapped) with one filename on each line of the file. img_wcs_ext : string or list of strings (Default = `SCI`) Extension name, extension name and version, or extension number of FITS extensions in the `images` to which the input regions `input_reg` should be mapped. The header of each extension must contain WCS information that will be used to convert `input_reg` from sky CS to image-like CS. Multiple extensions must be separated by semicolon while extension name and version (if present) must be separated by comma, e.g., `'SCI;DQ,1;0'`. When specifying the extension name only, internally it will be expanded into a list of extension names and versions for each version of that extension name present in the input `images`. For example, if a FITS file has four SCI and four DQ extensions, then `'SCI;DQ,1;0'` will be expanded into `'SCI,1;SCI,2;SCI,3;SCI,4;DQ,1;0'`. refimg : string (Default = ‘’) Reserved for future use. Filename of the reference image. May contain extension specifier: [extname,extver], [extname], or [extnumber]. Note This parameter is reserved for future use and it is not available through `TEAL` interface. ref_wcs_ext : string (Default = `SCI`) Reserved for future use. Extension name and/or version of FITS extensions in the `refimg` that contain WCS information that will be used to convert `input_reg` from image-like CS to sky CS. NOTE: Only extension name is allowed when `input_reg` is a list of region files that contain regions in image-like CS. In this case, the number of regions in `input_reg` must agree with the number of extensions with name specified by `ref_wcs_ext` present in the `refimg` FITS image. Note This parameter is reserved for future use and it is not available through `TEAL` interface. chip_reg : string or list of strings (Default = ‘’) Input region files in image CS associated with each extension specified by the `img_wcs_ext` parameter above. These regions will be added directly (without any transformation) to the `input_reg` regions mapped to each extension of the input `images`. These regions must be specified in image-like coordinates. Typically, these regions should contain “exclude” regions to exclude parts of the image specific to the detector chip (e.g., vignetted regions due to used filters, or occulting finger in ACS/HRC images) from being used for source finding. This paramater can be provided in one of the following forms: filename of a single image (if `img_wcs_ext` specifies a single FITS extension); comma-separated list of filenames (if `img_wcs_ext` specifies more than one extension) or `None` for extensions that do not need any chip-specific regions to be excluded/included; ‘’ (empty string) or None if no chip-specific region files are provided. The number of regions ideally must be equal to the number of extensions specified by the `img_wcs_ext` parameter. If the number of chip-specific regions is less than the number of `img_wcs_ext` extensions then ‘chip_reg’ regions will be assigned to the first extensions from `img_wcs_ext` (after internal expansion described in help for the `img_wcs_ext` parameter above). If the number of ‘chip_reg’ is larger than the number of `img_wcs_ext` extensions then extra regions will be ignored. outpath : string (Default = `./regions`) The directory to which the transformed regions should be saved. filter : string {‘None’, ‘fast’, or ‘precise’ } (Default = ‘None’) Specify whether or not to remove the regions in the transformed region files that are outside the image array. With the ‘fast’ mehod only intersection of the bounding boxes is being checked. Note The `'precise'` method is not implemented in this release and, if specified, defaults to ‘fast’. The `'precise'` option is not available through the `TEAL` interface. catfname : string (Default = `exclusions_cat.txt`) The file name of the output exclusions catalog file to be created from the supplied image and region file names. This file can be passed as an input to TweakReg task. Verify that the created file is correct! append : bool (Default = False) Specify whether or not to append the transformed regions to the existing region files with the same name. interactive : bool (Default = False) Reserved for future use. (This switch controls whether the program stops and waits for the user to examine any generated region files before continuing on to the next image.) Note This parameter is reserved for future use and it is not available through `TEAL` interface. verbose : bool (Default = False) Specify whether or not to print extra messages during processing.

  Notes

  NOTE 1: This task takes a region file (or multiple files) that describe(s) what regions of sky should be used for source finding (include regions) and what regions should be avoided (exclude regions) and transforms/maps this region file onto a number of image files that need to be alighned.

  The idea behind this task is automate the creation of region files that then can be passed to exclusions parameter of the `TweakReg` task.

  The same thing can be achieved manually using, for example, external FITS viewers, e.g., SAO DS9. For example, based on some image `refimg.fits` we can select a few small regions of sky that contain several good (bright, not saturated) point-like sources that could be used for image alignment of other images (say `img1.fits`, `img2.fits`, etc.). We can save this region file in sky coordinates (e.g., `fk5`), e.g., under the name `input_reg.reg`. We can then load a specific extension of each of the images `img1.fits`, `img2.fits`, etc. one by one into DS9 and then load onto those images the previously created include/exclude region file `input_reg.reg`. Now we can save the regions using image coordinates. To do conversion from the sky coordinates to image coordinates, DS9 will use the WCS info from the image onto which the region file was loaded. The `MapReg` task tries to automate this process.

  NOTE 2: `MapReg` relies on the `pyregion` package for region file parsing and coordinate transformation. Unfortunately, as of writing, pyregion does not consider distortion corrections when performing coordinate transformations. Therefore, there might be a slight discrepancy between the regions produced by `MapReg` and the DS9 regions obtained as described in the NOTE 1 above.

  NOTE 3: `MapReg` does not take into account pointing errors and thus the produced region files can be somewhat misaligned compared to their intended position around the sources identified in the “reference” image. Threfore, it is highly recommended that the produced region files be loaded into DS9 and their position be adjusted manually to include the sources of interest (or to avoid the regions that need to be avoided). If possible, the include or exclude regions should be large enough as to allow for most pointing errors.

  Examples

  Let’s say that based on some image `refimg.fits` we have produced a “master” reference image (`master.reg`) that includes regions around sources that we want to use for image alignment in task `TweakReg` and excludes regions that we want to avoid being used for image alignment (e.g, diffraction spikes, saturated quasars, stars, etc.). We save the file `master.reg` in sky CS (e.g., `fk5`).

  Also, let’s assume that we have a set of images `img1.fits`, `img2.fits`, etc. with four FITS extensions named ‘SCI’ and ‘DQ’. For some of the extensions, after analizing the `img*.fits` images we have identified parts of the chips that cannot be used for image alighnment. We create region files for those extensions and save the files in image CS as, e.g., `img1_chip_sci2.reg` (in our example this will be the only chip that needs “special” treatment).

  Finally, let’s say we want to “replicate” the “master” region file to all SCI exctensions of the `img*.fits` images as well as to the 2nd DQ extension and to the 8th extension of the `img*.fits` images.

  To do this we run:

      >>> mapreg(input_reg = 'master.reg', images='img*.fits',
      ...        img_wcs_ext='sci;dq,2;8', chip_reg='None,
      ...        img1_chip_sci2.reg,None,None,None,None')

  This will produce six region files in the ./regions subdirectory for each input image:

      ``img1_sci1_twreg.reg``,    ``img1_sci2_twreg.reg``,    ``img1_sci3_twreg.reg``,
      ``img1_sci4_twreg.reg``,    ``img1_dq2_twreg.reg``,     ``img1_extn8_twreg.reg``
      ...

      ``img2_sci1_twreg.reg``,    ``img2_sci2_twreg.reg``,    ``img2_sci3_twreg.reg``,
      ``img2_sci4_twreg.reg``,    ``img2_dq2_twreg.reg``,     ``img2_extn8_twreg.reg``
      ...

`drizzlepac.mapreg.``map_region_files`(input_reg, images, img_wcs_ext='sci', refimg=None, ref_wcs_ext='sci', chip_reg=None, outpath='./regions', filter=None, catfname=None, iteractive=False, append=False, verbose=True)

`drizzlepac.mapreg.``help`(file=None)

  Print out syntax help for running astrodrizzle

  Parameters: | file : str (Default = None) If given, write out help to the filename specified by this parameter Any previously existing file with this name will be deleted before writing out the help.