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crop(wcs=cube.extra_coords): dummy pixel components leak into points and errors #978
Description
Describe the bug
When cropping with wcs=cube.extra_coords, sanitize_crop_inputs pads each point with None for the dummy PIXEL components ndcube adds for array axes without extra coords. That shows up in a few ways:
- The count error counts the padding and (with Fix crop for WCSes with interleaved world objects #977) lists the dummy components. A 1-entry point on a 3-D cube with two extra coords on axis 0 reports "3 components ... 4 components", and passing the 4 listed entries reports "6 components".
- The correctly sized point
[time, None]fails withValueError: Number of world inputs (1) does not match expected (2)when the extra coords share an array axis. This is the same on main and with Fix crop for WCSes with interleaved world objects #977. - With the class matching from Fix crop for WCSes with interleaved world objects #977, a wrongly typed
Quantitygiven for aTimeextra coord matches the dummyQuantityslot and is moved there. Main raised a clearTypeError; now it raises aUnitConversionErroraboutpix, or, if the unit ispix, crops the dummy axis by pixel index.
One option for 1 and 3: in _get_crop_item, drop the trailing dummy components from the object list and the count, and re-append Nones after matching. That reads the private ExtraCoords._cube_array_axes_without_extra_coords, as sanitize_crop_inputs already does. 2 needs a separate fix in the default crop path.
To Reproduce
import numpy as np
import astropy.units as u
from astropy.time import Time
from astropy.wcs import WCS
from ndcube import NDCube
t = Time("2020-01-01") + np.arange(4) * u.s
def run(cube, label, *points):
try:
result = cube.crop(*points, wcs=cube.extra_coords).shape
except Exception as e:
result = f"{type(e).__name__}: {e}"
print(f"{label:28} -> {result}")
# Two extra coords sharing array axis 0 of a 3-D cube.
cube = NDCube(np.zeros((4, 5, 6)), wcs=WCS(naxis=3))
cube.extra_coords.add("time", 0, t)
cube.extra_coords.add("exposure", 0, np.arange(4) * u.s)
run(cube, "[time]", [t[1]], [t[2]])
run(cube, "[time, None]", [t[1], None], [t[2], None])
run(cube, "[time, None, None, None]", [t[1], None, None, None], [t[2], None, None, None])
run(cube, "[time, exposure]", [t[1], 1 * u.s], [t[2], 2 * u.s])
# One time extra coord on array axis 0 of a 2-D cube; a Quantity is the wrong type.
cube = NDCube(np.zeros((4, 5)), wcs=WCS(naxis=2))
cube.extra_coords.add("time", 0, t)
run(cube, "[time]", [t[1]], [t[2]])
run(cube, "[1 pix] (wrong type)", [1 * u.pix], [2 * u.pix])
run(cube, "[1 m] (wrong type)", [1 * u.m], [2 * u.m])On main (49b70c1):
[time] -> ValueError: 3 components in point 0 do not match WCS with 4 components.
[time, None] -> ValueError: Number of world inputs (1) does not match expected (2)
[time, None, None, None] -> ValueError: 6 components in point 0 do not match WCS with 4 components.
[time, exposure] -> (2, 5, 6)
[time] -> (2, 5)
[1 pix] (wrong type) -> TypeError: <class 'astropy.units.quantity.Quantity'> of component 0 in point 0 is incompatible with WCS component temporal_0 <class 'astropy.time.core.Time'>.
[1 m] (wrong type) -> TypeError: <class 'astropy.units.quantity.Quantity'> of component 0 in point 0 is incompatible with WCS component temporal_0 <class 'astropy.time.core.Time'>.
With #977:
[time] -> ValueError: 3 components in point 0 do not match WCS with 4 components. Each point must have one entry per world object (use None for a component that should not be cropped), in order: temporal_0 (Time), CUSTOM_0 (Quantity), pixel_1 (Quantity), pixel__1 (Quantity).
[time, None] -> ValueError: Number of world inputs (1) does not match expected (2)
[time, None, None, None] -> ValueError: 6 components in point 0 do not match WCS with 4 components. Each point must have one entry per world object (use None for a component that should not be cropped), in order: temporal_0 (Time), CUSTOM_0 (Quantity), pixel_1 (Quantity), pixel__1 (Quantity).
[time, exposure] -> (2, 5, 6)
[time] -> (2, 5)
[1 pix] (wrong type) -> (4, 2)
[1 m] (wrong type) -> UnitConversionError: 'm' (length) and 'pix' are not convertible
Screenshots
No response
System Details
- ndcube version: main (49b70c1) and Fix crop for WCSes with interleaved world objects #977
- astropy version: 7.2.0
- relevant package version(s): numpy 2.4.4, gwcs 1.0.3
- Python version: 3.14.4
- OS information: macOS
Installation method
git checkout
Activity