File-format-agnostic loading of astronomical images (pwkit.astimage
)¶
pwkit.astimage – generic loading of (radio) astronomical images
Use open (path, mode) to open an astronomical image, regardless of its file format.
The emphasis of this module is on getting 90%-good-enough semantics and a really, genuinely, uniform interface. This can be tough to achieve.
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class
pwkit.astimage.
AstroImage
(path, mode)[source]¶ An astronomical image.
- path
- The filesystem path of the image.
- mode
- Its access mode: ‘r’ for read, ‘rw’ for read/write.
- shape
- The data shape, like numpy.ndarray.shape.
- bmaj
- If not None, the restoring beam FWHM major axis in radians.
- bmin
- If not None, the restoring beam FWHM minor axis in radians.
- bpa
- If not None, the restoring beam position angle (east from celestial north) in radians.
- units
- Lower-case string describing image units (e.g., jy/beam, jy/pixel). Not standardized between formats.
- pclat
- Latitude (usually dec) of the pointing center in radians.
- pclon
- Longitude (usually RA) of the pointing center in radians.
- charfreq
- Characteristic observing frequency of the image in GHz.
- mjd
- Mean MJD of the observations.
- axdescs
- If not None, list of strings describing the axis types. Not standardized.
- size
- The number of pixels in the image (=shape.prod ()).
Methods:
- close
- Close the image.
- read
- Read all of the data.
- write
- Rewrite all of the data.
- toworld
- Convert pixel coordinates to world coordinates.
- topixel
- Convert world coordinates to pixel coordinates.
- simple
- Convert to a 2D lat/lon image.
- subimage
- Extract a sub-cube of the image.
- save_copy
- Save a copy of the image.
- save_as_fits
- Save a copy of the image in FITS format.
- delete
- Delete the on-disk image.
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axdescs
= None¶ If not None, list of strings describing the axis types; no standard format.
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bmaj
= None¶ If not None, the restoring beam FWHM major axis in radians
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bmin
= None¶ If not None, the restoring beam FWHM minor axis in radians
-
bpa
= None¶ If not None, the restoring beam position angle (east from celestial north) in radians
-
charfreq
= None¶ Characteristic observing frequency of the image in GHz
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mjd
= None¶ Mean MJD of the observations
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pclat
= None¶ Latitude of the pointing center in radians
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pclon
= None¶ Longitude of the pointing center in radians
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shape
= None¶ An integer ndarray of the image shape
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subimage
(pixofs, shape)[source]¶ Extract a sub-cube of this image.
Both pixofs and shape should be integer arrays with as many elements as this image has axes. Thinking of this operation as taking a Python slice of an N-dimensional cube, the i’th axis of the sub-image is slices from pixofs[i] to pixofs[i] + shape[i].
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units
= None¶ Lower-case string describing image units (e.g., jy/beam, jy/pixel)
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class
pwkit.astimage.
MIRIADImage
(path, mode)[source]¶ A MIRIAD format image. Requires the mirtask module from miriad-python.