# Licensed under a 3-clause BSD style license - see LICENSE.rst import os from astropy import log from astropy.io.fits import getdata from astropy.visualization.mpl_normalize import simple_norm __all__ = ["fits2bitmap", "main"] def fits2bitmap( filename, ext=0, out_fn=None, stretch="linear", power=1.0, asinh_a=0.1, min_cut=None, max_cut=None, min_percent=None, max_percent=None, percent=None, cmap="Greys_r", ): """ Create a bitmap file from a FITS image, applying a stretching transform between minimum and maximum cut levels and a matplotlib colormap. Parameters ---------- filename : str The filename of the FITS file. ext : int FITS extension name or number of the image to convert. The default is 0. out_fn : str The filename of the output bitmap image. The type of bitmap is determined by the filename extension (e.g. '.jpg', '.png'). The default is a PNG file with the same name as the FITS file. stretch : {'linear', 'sqrt', 'power', log', 'asinh'} The stretching function to apply to the image. The default is 'linear'. power : float, optional The power index for ``stretch='power'``. The default is 1.0. asinh_a : float, optional For ``stretch='asinh'``, the value where the asinh curve transitions from linear to logarithmic behavior, expressed as a fraction of the normalized image. Must be in the range between 0 and 1. The default is 0.1. min_cut : float, optional The pixel value of the minimum cut level. Data values less than ``min_cut`` will set to ``min_cut`` before stretching the image. The default is the image minimum. ``min_cut`` overrides ``min_percent``. max_cut : float, optional The pixel value of the maximum cut level. Data values greater than ``min_cut`` will set to ``min_cut`` before stretching the image. The default is the image maximum. ``max_cut`` overrides ``max_percent``. min_percent : float, optional The percentile value used to determine the pixel value of minimum cut level. The default is 0.0. ``min_percent`` overrides ``percent``. max_percent : float, optional The percentile value used to determine the pixel value of maximum cut level. The default is 100.0. ``max_percent`` overrides ``percent``. percent : float, optional The percentage of the image values used to determine the pixel values of the minimum and maximum cut levels. The lower cut level will set at the ``(100 - percent) / 2`` percentile, while the upper cut level will be set at the ``(100 + percent) / 2`` percentile. The default is 100.0. ``percent`` is ignored if either ``min_percent`` or ``max_percent`` is input. cmap : str The matplotlib color map name. The default is 'Greys_r'. """ import matplotlib import matplotlib.image as mimg from astropy.utils.introspection import minversion # __main__ gives ext as a string try: ext = int(ext) except ValueError: pass try: image = getdata(filename, ext) except Exception as e: log.critical(e) return 1 if image.ndim != 2: log.critical(f"data in FITS extension {ext} is not a 2D array") if out_fn is None: out_fn = os.path.splitext(filename)[0] if out_fn.endswith(".fits"): out_fn = os.path.splitext(out_fn)[0] out_fn += ".png" # explicitly define the output format out_format = os.path.splitext(out_fn)[1][1:] try: if minversion(matplotlib, "3.5"): matplotlib.colormaps[cmap] else: from matplotlib import cm cm.get_cmap(cmap) except (ValueError, KeyError): log.critical(f"{cmap} is not a valid matplotlib colormap name.") return 1 norm = simple_norm( image, stretch=stretch, power=power, asinh_a=asinh_a, min_cut=min_cut, max_cut=max_cut, min_percent=min_percent, max_percent=max_percent, percent=percent, ) mimg.imsave(out_fn, norm(image), cmap=cmap, origin="lower", format=out_format) log.info(f"Saved file to {out_fn}.") def main(args=None): import argparse parser = argparse.ArgumentParser( description="Create a bitmap file from a FITS image." ) parser.add_argument( "-e", "--ext", metavar="hdu", default=0, help="Specify the HDU extension number or name (Default is 0).", ) parser.add_argument( "-o", metavar="filename", type=str, default=None, help=( "Filename for the output image (Default is a " "PNG file with the same name as the FITS file)." ), ) parser.add_argument( "--stretch", type=str, default="linear", help=( 'Type of image stretching ("linear", "sqrt", ' '"power", "log", or "asinh") (Default is "linear").' ), ) parser.add_argument( "--power", type=float, default=1.0, help='Power index for "power" stretching (Default is 1.0).', ) parser.add_argument( "--asinh_a", type=float, default=0.1, help=( "The value in normalized image where the asinh " "curve transitions from linear to logarithmic " 'behavior (used only for "asinh" stretch) ' "(Default is 0.1)." ), ) parser.add_argument( "--min_cut", type=float, default=None, help="The pixel value of the minimum cut level (Default is the image minimum).", ) parser.add_argument( "--max_cut", type=float, default=None, help="The pixel value of the maximum cut level (Default is the image maximum).", ) parser.add_argument( "--min_percent", type=float, default=None, help=( "The percentile value used to determine the " "minimum cut level (Default is 0)." ), ) parser.add_argument( "--max_percent", type=float, default=None, help=( "The percentile value used to determine the " "maximum cut level (Default is 100)." ), ) parser.add_argument( "--percent", type=float, default=None, help=( "The percentage of the image values used to " "determine the pixel values of the minimum and " "maximum cut levels (Default is 100)." ), ) parser.add_argument( "--cmap", metavar="colormap_name", type=str, default="Greys_r", help='matplotlib color map name (Default is "Greys_r").', ) parser.add_argument( "filename", nargs="+", help="Path to one or more FITS files to convert" ) args = parser.parse_args(args) for filename in args.filename: fits2bitmap( filename, ext=args.ext, out_fn=args.o, stretch=args.stretch, min_cut=args.min_cut, max_cut=args.max_cut, min_percent=args.min_percent, max_percent=args.max_percent, percent=args.percent, power=args.power, asinh_a=args.asinh_a, cmap=args.cmap, )