def rotate(infile, outfile, angle, xcen=None, ycen=None):
# Open the FITS file using pyfits. A list of the HDUs in the FITS file is
# returned.
hdu_list = pyfits.open(infile)
# Create an object that will transfer FITS header cards between an AST
# FitsChan and the PyFITS header describing the primary HDU of the
# supplied FITS file.
adapter = Atl.PyFITSAdapter(hdu_list[0])
# Create a FitsChan and use the above adapter to copy all the header
# cards into it.
fitschan = Ast.FitsChan(adapter, adapter)
# Get the flavour of FITS-WCS used by the header cards currently in the
# FitsChan. This is so that we can use the same flavour when we write
# out the modified WCS.
encoding = fitschan.Encoding
# Read WCS information from the FitsChan. Additionally, this removes all
# WCS information from the FitsChan. The returned wcsinfo object
# is an AST FrameSet, in which the current Frame describes WCS coordinates
# and the base Frame describes pixel coodineates. The FrameSet includes a
# Mapping that specifies the transformation between the two Frames.
wcsinfo = fitschan.read()
# Check that the FITS header contained WCS in a form that can be
# understood by AST.
if wcsinfo == None:
print("Failed to read WCS information from {0}".format(infile))
# Rotation is restricted to 2D arrays, so check the FITS file has 2 pixel
# axes (given by Nin) and 2 WCS axes (given by Nout).
elif wcsinfo.Nin != 2 or wcsinfo.Nout != 2:
print("{0} is not 2-dimensional".format(infile))
# Proceed if the WCS information was read OK.
else:
# Get the lower and upper bounds of the input image in pixel indices.
# All FITS arrays by definition have lower pixel bounds of [1,1] (unlike
# NDFs). Note, unlike pyfits AST uses FITS ordering for storing pixel axis
# values in an array (i.e. NAXIS1 first, NAXIS2 second, etc).
lbnd_in = [1, 1]
ubnd_in = [fitschan["NAXIS1"], fitschan["NAXIS2"]]
# Get the rotation angle and convert from degrees to radians.
angle = float(angle) * Ast.DD2R
# Construct a MatrixMap that rotates by the required angle, converted to radians.
sinang = math.sin(angle)
cosang = math.cos(angle)
pixmap = Ast.MatrixMap([[cosang, sinang], [-sinang, cosang]])
# If supplied, get the centre of rotation.
if (xcen is not None) and (ycen is not None):
# Create aShiftMap to shift the origin and combine it with the
# MatrixMap, to give the desired centre of rotation (shift,
# rotate, then shift back again).
shiftmap = Ast.ShiftMap([-xcen, -ycen])
pixmap = Ast.CmpMap(shiftmap, pixmap)
shiftmap.invert()
pixmap = Ast.CmpMap(pixmap, shiftmap)
# The dimensions of the output array are the same as the input array.
lbnd_out = lbnd_in
ubnd_out = ubnd_in
# If no centre of rotation was specified, we use the MatrixMap
# unchanged, and determine the bounds of the smallest output image that
# will hold the entire rotated input image. These are with respect to
# the pixel coordinates of the input array, and so some corners may have
# negative pixel coordinates.
else:
(lb1, ub1, xl, xu) = pixmap.mapbox(lbnd_in, ubnd_in, 1)
(lb2, ub2, xl, xu) = pixmap.mapbox(lbnd_in, ubnd_in, 2)
lbnd_out = [int(lb1), int(lb2)]
ubnd_out = [int(ub1), int(ub2)]
# Get the value used to represent missing pixel values
if "BLANK" in fitschan:
badval = fitschan["BLANK"]
flags = Ast.USEBAD
else:
badval = 0
flags = 0
# Resample the data array using the above mapping.
(npix, out, out_var) = pixmap.resample(lbnd_in, ubnd_in,
hdu_list[0].data, None,
Ast.LINEAR, None, flags, 0.05,
1000, badval, lbnd_out,
ubnd_out, lbnd_out, ubnd_out)
# Store the rotated data in the HDU, and update the NAXISi keywords
# to hold the number of pixels along each edge of the rotated image.
hdu_list[0].data = out
fitschan["NAXIS1"] = ubnd_out[0] - lbnd_out[0] + 1
fitschan["NAXIS2"] = ubnd_out[1] - lbnd_out[1] + 1
# Move the pixel origin of the output from "lbnd_out" to (1,1). Create a
# suitable ShiftMap, and append it to the total "old pixel coord" to
# "new pixel coords" mapping.
shiftmap = Ast.ShiftMap([-lbnd_out[0], -lbnd_out[1]])
pixmap = Ast.CmpMap(pixmap, shiftmap)
# Re-map the base Frame (i.e. the pixel coordinates Frame) so that it
# refers to the new data grid instead of the old one.
wcsinfo.remapframe(Ast.BASE, pixmap)
# Attempt to write the modified WCS information to the primary HDU (i.e.
# convert the FrameSet to a set of FITS header cards stored in the
# FITS file). Indicate that we want to use original flavour of FITS-WCS.
fitschan.Encoding = encoding
fitschan.clear('Card')
if fitschan.write(wcsinfo) == 0:
print("Failed to convert the rotated WCS to Fits-WCS")
# If successfull, force the FitsCHan to copy its contents into the
# PyFITS header, then write the changed data and header to the output
# FITS file.
else:
fitschan.writefits()
hdu_list.writeto(outfile, clobber=True, output_verify='ignore')
else:
# Get the lower and upper bounds of the input image in pixel indices.
# All FITS arrays by definition have lower pixel bounds of [1,1] (unlike
# NDFs). Note, unlike pyfits AST uses FITS ordering for storing pixel axis
# values in an array (i.e. NAXIS1 first, NAXIS2 second, etc).
lbnd_in = [ 1, 1 ]
ubnd_in = [ fitschan["NAXIS1"], fitschan["NAXIS2"] ]
# Get the rotation angle and convert from degrees to radians.
angle = float( sys.argv[3] )*Ast.DD2R
# Construct a MatrixMap that rotates by the required angle, converted to radians.
sinang = math.sin( angle )
cosang = math.cos( angle )
pixmap = Ast.MatrixMap( [ [cosang,sinang], [-sinang,cosang] ] )
# If supplied, get the centre of rotation.
if len(sys.argv) > 5:
x0 = float( sys.argv[4] )
y0 = float( sys.argv[5] )
# Create aShiftMap to shift the origin and combine it with the
# MatrixMap, to give the desired centre of rotation (shift,
# rotate, then shift back again).
shiftmap = Ast.ShiftMap( [ -x0, -y0 ] )
pixmap = Ast.CmpMap( shiftmap, pixmap );
shiftmap.invert()
pixmap = Ast.CmpMap( pixmap, shiftmap );
# The dimensions of the output array are the same as the input array.