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# Licensed under a 3-clause BSD style license - see LICENSE.rst
from __future__ import print_function, division, absolute_import
import numpy as np
from ... import units as u
from ...extern import six
from ...coordinates import BaseCoordinateFrame
# Modified from axis_artist, supports astropy.units
def select_step_degree(dv):
# Modified from axis_artist, supports astropy.units
if dv > 1. * u.arcsec:
degree_limits_ = [1.5, 3, 7, 13, 20, 40, 70, 120, 270, 520]
degree_steps_ = [1, 2, 5, 10, 15, 30, 45, 90, 180, 360]
degree_units = [u.degree] * len(degree_steps_)
minsec_limits_ = [1.5, 2.5, 3.5, 8, 11, 18, 25, 45]
minsec_steps_ = [1, 2, 3, 5, 10, 15, 20, 30]
minute_limits_ = np.array(minsec_limits_) / 60.
minute_units = [u.arcmin] * len(minute_limits_)
second_limits_ = np.array(minsec_limits_) / 3600.
second_units = [u.arcsec] * len(second_limits_)
degree_limits = np.concatenate([second_limits_,
minute_limits_,
degree_limits_])
degree_steps = minsec_steps_ + minsec_steps_ + degree_steps_
degree_units = second_units + minute_units + degree_units
n = degree_limits.searchsorted(dv.to(u.degree))
step = degree_steps[n]
unit = degree_units[n]
return step * unit
else:
return select_step_scalar(dv.to(u.arcsec).value) * u.arcsec
def select_step_hour(dv):
if dv > 15. * u.arcsec:
hour_limits_ = [1.5, 2.5, 3.5, 5, 7, 10, 15, 21, 36]
hour_steps_ = [1, 2, 3, 4, 6, 8, 12, 18, 24]
hour_units = [u.hourangle] * len(hour_steps_)
minsec_limits_ = [1.5, 2.5, 3.5, 4.5, 5.5, 8, 11, 14, 18, 25, 45]
minsec_steps_ = [1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30]
minute_limits_ = np.array(minsec_limits_) / 60.
minute_units = [15. * u.arcmin] * len(minute_limits_)
second_limits_ = np.array(minsec_limits_) / 3600.
second_units = [15. * u.arcsec] * len(second_limits_)
hour_limits = np.concatenate([second_limits_,
minute_limits_,
hour_limits_])
hour_steps = minsec_steps_ + minsec_steps_ + hour_steps_
hour_units = second_units + minute_units + hour_units
n = hour_limits.searchsorted(dv.to(u.hourangle))
step = hour_steps[n]
unit = hour_units[n]
return step * unit
else:
return select_step_scalar(dv.to(15. * u.arcsec).value) * (15. * u.arcsec)
def select_step_scalar(dv):
log10_dv = np.log10(dv)
base = np.floor(log10_dv)
frac = log10_dv - base
steps = np.log10([1, 2, 5, 10])
imin = np.argmin(np.abs(frac - steps))
return 10. ** (base + steps[imin])
def get_coord_meta(frame):
coord_meta = {}
coord_meta['type'] = ('longitude', 'latitude')
coord_meta['wrap'] = (None, None)
coord_meta['unit'] = (u.deg, u.deg)
from astropy.coordinates import frame_transform_graph
if isinstance(frame, six.string_types):
initial_frame = frame
frame = frame_transform_graph.lookup_name(frame)
if frame is None:
raise ValueError("Unknown frame: {0}".format(initial_frame))
if not isinstance(frame, BaseCoordinateFrame):
frame = frame()
names = list(frame.representation_component_names.keys())
coord_meta['name'] = names[:2]
return coord_meta
def coord_type_from_ctype(ctype):
"""
Determine whether a particular WCS ctype corresponds to an angle or scalar
coordinate.
"""
if ctype[:4] in ['RA--'] or ctype[1:4] == 'LON':
return 'longitude', None
elif ctype[:4] in ['HPLN']:
return 'longitude', 180.
elif ctype[:4] in ['DEC-', 'HPLT'] or ctype[1:4] == 'LAT':
return 'latitude', None
else:
return 'scalar', None
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