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| -rw-r--r-- | fg21sim/utils/wcs.py | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/fg21sim/utils/wcs.py b/fg21sim/utils/wcs.py new file mode 100644 index 0000000..b4a9ed1 --- /dev/null +++ b/fg21sim/utils/wcs.py @@ -0,0 +1,54 @@ +# Copyright (c) 2017 Weitian LI <weitian@aaronly.me> +# MIT license + +""" +Create WCS for sky projection. +""" + +import numpy as np +from astropy.wcs import WCS + + +def make_wcs(center, size, pixelsize, frame="ICRS", projection="TAN"): + """ + Make WCS for sky projection usages, etc. + + Parameters + ---------- + center : (xcenter, ycenter) float tuple + The equatorial/galactic coordinate of the sky/image center [ deg ]. + size : (xsize, ysize) int tuple + The size (width, height) of the sky/image. + pixelsize : float + The pixel size of the sky/image [ arcmin ] + frame : str, "ICRS" or "Galactic" + The coordinate frame, only one of ``ICRS`` or ``Galactic``. + projection : str, "TAN" or "CAR" + The projection algorithm used by the sky/image, currently only + support ``TAN`` (tangential), ``CAR`` (Cartesian). + + Returns + ------- + w : `~astropy.wcs.WCS` + Created WCS header/object + """ + xcenter, ycenter = center # [ deg ] + xsize, ysize = size + delt = pixelsize / 60.0 # [ deg ] + if projection.upper() not in ["TAN", "CAR"]: + raise ValueError("unsupported projection: " % projection) + if frame.upper() == "ICRS": + ctype = ["RA---" + projection.upper(), "DEC--" + projection.upper()] + elif frame.upper() == "GALACTIC": + ctype = ["GLON-" + projection.upper(), "GLAT-" + projection.upper()] + else: + raise ValueError("unknown frame: " % frame) + + w = WCS(naxis=2) + w.wcs.ctype = ctype + w.wcs.crval = np.array([xcenter, ycenter]) + w.wcs.crpix = np.array([xsize/2.0-0.5, ysize/2.0-0.5]) + w.wcs.cdelt = np.array([-delt, delt]) + w.wcs.cunit = ["deg", "deg"] + w.wcs.equinox = 2000.0 + return w |