XSnap

XSnap - Create Snapshots of Astronomical Sources

Space Telescope Science Institute

Synopsis

Create PNG images (and optionally FITS cutouts) of astronomical sources from FITS images, with optional region overlays.

Command Line Usage

XSnap.py [-size arcmin] [-type suffix] [-min vmin] [-max vmax] [-o outname] image.fits master_table
XSnap.py [-size arcmin] [-type suffix] [-min vmin] [-max vmax] snapshot_table region_table

Modes

The script operates in three modes depending on the inputs:

Overview mode (FITS file + master table, no -size): Creates a single PNG of the full FITS image with regions from the master table overlaid.

Example:
```
XSnap.py -o lmc_ha_overview DECam_SWARP/LMC_c42_T01.ha.fits config/lmc_snr.txt
```
Output: lmc_ha_overview.png
Snapshot mode (FITS file + master table + -size): Creates one PNG snapshot per source in the master table, all extracted from the same FITS image. Also creates FITS cutouts in xdata/.

Example:
```
XSnap.py -size 10 -type ha -min -1 -max 20 DECam_SWARP/LMC_c42_T01.ha.fits config/lmc_snr.txt
```
Output: ximage/{Source_name}.ha.png for each source, plus FITS cutouts in xdata/
Multi-file snapshot mode (snapshot table + region table, no FITS file): The snapshot table must contain a filename column specifying a different FITS file for each source. Creates one PNG per row using the corresponding FITS file.

Example:
```
XSnap.py -size 10 -type ha snapshots.txt config/lmc_snr.txt
```
Where snapshots.txt contains columns: Source_name, RA, Dec, filename

Optional Arguments:

-size arcmin: Size of snapshot cutouts in arcminutes. Required for snapshot modes.
-type suffix: Suffix appended to output filenames (e.g., “ha” produces Source.ha.png). Useful for distinguishing filter/image types.

-o outname: Base name for output file in overview mode (produces outname.png).

-min vmin: Minimum value for image scaling. Default: 5th percentile.
-max vmax: Maximum value for image scaling. Default: 95th percentile.

Input Tables

Master/region tables must contain at minimum: Source_name, RA, Dec

For region overlays, tables may also include: - RegType: “circle” or “ellipse” - Major, Minor: region sizes in arcseconds - Theta: position angle for ellipses

Output

PNG images are written to ximage/ (snapshots) or current directory (overview)
FITS cutouts are written to xdata/ (snapshot modes only)

Functions

`display_fits_image`(image_file[, scale, ymin, ymax, ...])
`extract_region`(source_name, ra, dec, size_arcmin, ...)	Extract a region of a given size, but do not write an image if a fraction of an
`make_many_images`(filename, master, xtype, size, ymin, ymax)	Create cut-outs of an image, one for each source in a masterfile
`make_many_images2`(master, reg, xtype, size, ymin, ymax)	Create cut-outs of an image, one for each line in a mastefile
`make_one_image`(filename, master, ymin, ymax[, outroot])	Create a plot of an image and overlay the retions
`steer`(argv)	XSnap.py [-size 10] [-type ha] [-min -1] [-max 20] -out ha [filename or table of snaps] master_table_of_regions

Module Contents

XSnap.display_fits_image(image_file, scale='linear', ymin=None, ymax=None, invert=True, masterfile='', outfile='')

XSnap.extract_region(source_name, ra, dec, size_arcmin, input_fits, outdir='test', default_value=0, frac_off=0.1): Extract a region of a given size, but do not write an image if a fraction of an image has not data exceeds frac_off

XSnap.make_many_images(filename, master, xtype, size, ymin, ymax, frac_off=0.1): Create cut-outs of an image, one for each source in a masterfile and overlay the regions from the master file on each sanpshot.

XSnap.make_many_images2(master, reg, xtype, size, ymin, ymax): Create cut-outs of an image, one for each line in a mastefile and overlay the regions from the master file on each sanpshot.

XSnap.make_one_image(filename, master, ymin, ymax, outroot=''): Create a plot of an image and overlay the retions from a master file on it.

XSnap.steer(argv)

XSnap.py [-size 10] [-type ha] [-min -1] [-max 20] -out ha [filename or table of snaps] master_table_of_regions

without - size we use the full image, and just display eveything with a size we make images of each of the source in the master tale