# Licensed under a 3-clause BSD style license - see LICENSE.rst
"""
A module for searching for images in a remote archive.
A Simple Image Access (SIA) service allows a client to search for
images in an archive whose field of view overlaps with a given
rectangular region on the sky. The service responds to a search query
with a table in which each row represents an image that is available
for download. The columns provide metadata describing each image and
one column in particular provides the image's download URL (also
called the *access reference*, or *acref*). Some SIA services act as
a cut-out service; in this case, the query result is a table of images
whose field of view matches the requested region and which will be
created when accessed via the download URL.
This module provides an interface for accessing an SIA service. It is
implemented as a specialization of the DAL Query interface.
The ``search()`` function support the simplest and most common types
of queries, returning an SIAResults instance as its results which
represents the matching images from the archive. The SIAResults
supports access to and iterations over the individual records; these
are provided as SIARecord instances, which give easy access to key
metadata in the response, such as the position of the image's center,
the image format, the size and shape of the image, and its download
URL.
The ``SIAService`` class can represent a specific service available at a URL
endpoint.
"""
import re
from pyvo.io.vosi.vodataservice import TableParam
from astropy.coordinates import SkyCoord
from astropy.time import Time
from astropy.units import Quantity, Unit
from .query import DALResults, DALQuery, DALService, Record
from .mimetype import mime2extension
from .adhoc import DatalinkResultsMixin, DatalinkRecordMixin, SodaRecordMixin
from .. import samp
__all__ = ["search", "SIAService", "SIAQuery", "SIAResults", "SIARecord"]
def search(
url, pos, *, size=1.0, format=None, intersect=None, verbosity=2,
**keywords):
"""
submit a simple SIA query that requests images overlapping a given region
Parameters
----------
url : str
the base URL for the SIA service
pos : `~astropy.coordinates.SkyCoord` class or sequence of two floats
the position of the center of the rectangular search region.
assuming icrs decimal degrees if unit is not specified.
size : `~astropy.units.Quantity` class or up to 2 floats.
the full rectangular size of the search region along the
RA and Dec directions.
converted if it's a iterable containing scalars,
assuming decimal degrees.
format : str
the image format(s) of interest. "all" (server-side default)
indicates all available formats; "graphic" indicates
graphical images (e.g. jpeg, png, gif; not FITS);
"metadata" indicates that no images should be
returned--only an empty table with complete metadata;
"image/\\*" indicates a particular image format where
* can have values like "fits", "jpeg", "png", etc.
intersect : str
a token indicating how the returned images should
intersect with the search region; recognized values include:
========= ======================================================
COVERS select images that completely cover the search region
ENCLOSED select images that are complete enclosed by the region
OVERLAPS select any image that overlaps the search region (server-side default)
CENTER select images whose center is within the search region
========= ======================================================
verbosity : int
an integer value that indicates the volume of columns
to return in the result table. 0 means the minimum
set of columsn, 3 means as many columns as are available.
(client-side default == 2)
**keywords :
additional parameters can be given via arbitrary
case insensitive keyword arguments. Where there is overlap
with the parameters set by the other arguments to
this function, these keywords will override.
Returns
-------
SIAResults
a container holding a table of matching image records
Raises
------
DALServiceError
for errors connecting to or communicating with the service
DALQueryError
if the service responds with an error,
including a query syntax error.
See Also
--------
SIAResults
pyvo.dal.DALServiceError
pyvo.dal.DALQueryError
"""
service = SIAService(url)
return service.search(pos=pos, size=size, format=format, intersect=intersect,
verbosity=verbosity, **keywords)
[docs]class SIAService(DALService):
"""
a representation of an SIA service
"""
def __init__(self, baseurl, *, capability_description=None, session=None):
"""
instantiate an SIA service
Parameters
----------
baseurl : str
the base URL for submitting search queries to the service.
session : object
optional session to use for network requests
"""
super().__init__(baseurl, capability_description=capability_description, session=session)
self._description = capability_description
def _get_metadata(self):
"""
the metadata resource element
"""
if not hasattr(self, "_metadata"):
query = self.create_query(format='metadata')
metadata = query.execute_votable()
setattr(self, "_metadata", metadata)
try:
setattr(self, "_metadata_resource", metadata.resources[0])
except IndexError:
setattr(self, "_metadata_resource", None)
@property
def description(self):
"""
the service description.
"""
self._get_metadata()
try:
return getattr(self, "_metadata", None).description
except AttributeError:
return None
@property
def params(self):
"""
the service parameters.
"""
self._get_metadata()
try:
return getattr(self, "_metadata_resource", None).params
except AttributeError:
return None
@property
def columns(self):
"""
the available columns on this service
"""
self._get_metadata()
fields = getattr(self, '_metadata', None).get_first_table().fields
try:
return [
TableParam.from_field(field) for field in fields]
except AttributeError:
return []
[docs] def search(
self, pos, *, size=1.0, format=None, intersect=None,
verbosity=2, **keywords):
"""
submit a SIA query to this service with the given parameters.
Parameters
----------
pos : `~astropy.coordinates.SkyCoord` class or sequence of two floats
the position of the center of the rectangular search region.
assuming icrs decimal degrees if unit is not specified.
size : `~astropy.units.Quantity` class or up to 2 floats.
the full rectangular size of the search region along the
RA and Dec directions.
converted if it's a iterable containing scalars,
assuming decimal degrees.
size : `~astropy.units.Quantity` class or scalar float
the size of the rectangular region around pos.
assuming icrs decimal degrees if unit is not specified.
format : str
the image format(s) of interest. "all" (server-side default)
indicates all available formats; "graphic" indicates
graphical images (e.g. jpeg, png, gif; not FITS);
"metadata" indicates that no images should be
returned--only an empty table with complete metadata;
"image/\\*" indicates a particular image format where
* can have values like "fits", "jpeg", "png", etc.
intersect : str
a token indicating how the returned images should
intersect with the search region; recognized values include:
========= ======================================================
COVERS select images that completely cover the search region
ENCLOSED select images that are complete enclosed by the region
OVERLAPS select any image that overlaps the search region (server-side default)
CENTER select images whose center is within the search region
========= ======================================================
verbosity : int
an integer value that indicates the volume of columns
to return in the result table. 0 means the minimum
set of columns, 3 means as many columns as are available.
(client-side default == 2)
**keywords :
additional parameters can be given via arbitrary
case insensitive keyword arguments. Where there is overlap
with the parameters set by the other arguments to
this function, these keywords will override.
Returns
-------
SIAResults
a container holding a table of matching catalog records
Raises
------
DALServiceError
for errors connecting to or communicating with the service
DALQueryError
if the service responds with an error,
including a query syntax error.
See Also
--------
SIAResults
pyvo.dal.DALServiceError
pyvo.dal.DALQueryError
"""
return self.create_query(
pos=pos, size=size, format=format, intersect=intersect, verbosity=verbosity, **keywords).execute()
[docs] def create_query(
self, pos=None, *, size=None, format=None, intersect=None,
verbosity=None, **keywords):
"""
create a query object that constraints can be added to and then
executed. The input arguments will initialize the query with the
given values.
Parameters
----------
pos : `~astropy.coordinates.SkyCoord` class or sequence of two floats
the position of the center of the rectangular search region.
assuming icrs decimal degrees if unit is not specified.
size : `~astropy.units.Quantity` class or up to 2 floats.
the full rectangular size of the search region along the
RA and Dec directions.
converted if it's a iterable containing scalars,
assuming decimal degrees.
size : `~astropy.units.Quantity` class or scalar float
the size of the rectangular region around pos.
assuming icrs decimal degrees if unit is not specified.
format : str
the image format(s) of interest. "all" (server-side default)
indicates all available formats; "graphic" indicates
graphical images (e.g. jpeg, png, gif; not FITS);
"metadata" indicates that no images should be
returned--only an empty table with complete metadata;
"image/\\*" indicates a particular image format where
* can have values like "fits", "jpeg", "png", etc.
intersect : str
a token indicating how the returned images should
intersect with the search region; recognized values include:
========= ======================================================
COVERS select images that completely cover the search region
ENCLOSED select images that are complete enclosed by the region
OVERLAPS select any image that overlaps the search region (server-side default)
CENTER select images whose center is within the search region
========= ======================================================
verbosity : int
an integer value that indicates the volume of columns
to return in the result table. 0 means the minimum
set of columsn, 3 means as many columns as are available.
**keywords :
additional parameters can be given via arbitrary
case insensitive keyword arguments. Where there is overlap
with the parameters set by the other arguments to
this function, these keywords will override.
Returns
-------
SIAQuery
the query instance
See Also
--------
SIAQuery
"""
return SIAQuery(
self.baseurl, pos=pos, size=size, format=format, intersect=intersect,
verbosity=verbosity, session=self._session, **keywords)
[docs] def describe(self):
print(self.description)
print()
[docs]class SIAQuery(DALQuery):
"""
a class for preparing an query to an SIA service. Query constraints
are added via its service type-specific methods. The various execute()
functions will submit the query and return the results.
The base URL for the query, which controls where the query will be sent
when one of the execute functions is called, is typically set at
construction time; however, it can be updated later via the
:py:attr:`~pyvo.dal.DALQuery.baseurl` to send a configured
query to another service.
In addition to the search constraint attributes described below, search
parameters can be set generically by name via dict semantics.
The typical function for submitting the query is ``execute()``; however,
alternate execute functions provide the response in different forms,
allowing the caller to take greater control of the result processing.
"""
def __init__(
self, baseurl, pos=None, *, size=None, format=None, intersect=None,
verbosity=None, session=None, **keywords):
"""
initialize the query object with a baseurl and the given parameters
Parameters
----------
baseurl : str
the base URL for the SIA service
pos : `~astropy.coordinates.SkyCoord` class or sequence of two floats
the position of the center of the rectangular search region.
assuming icrs decimal degrees if unit is not specified.
size : `~astropy.units.Quantity` class or up to 2 floats.
the full rectangular size of the search region along the
RA and Dec directions.
converted if it's a iterable containing scalars,
assuming decimal degrees.
size : `~astropy.units.Quantity` class or scalar float
the size of the rectangular region around pos.
assuming icrs decimal degrees if unit is not specified.
format : str
the image format(s) of interest. "all" (server-side default)
indicates all available formats; "graphic" indicates
graphical images (e.g. jpeg, png, gif; not FITS);
"metadata" indicates that no images should be
returned--only an empty table with complete metadata;
"image/\\*" indicates a particular image format where
* can have values like "fits", "jpeg", "png", etc.
intersect : str
a token indicating how the returned images should
intersect with the search region; recognized values include:
========= ======================================================
COVERS select images that completely cover the search region
ENCLOSED select images that are complete enclosed by the region
OVERLAPS select any image that overlaps the search region (server-side default)
CENTER select images whose center is within the search region
========= ======================================================
verbosity : int
an integer value that indicates the volume of columns
to return in the result table. 0 means the minimum
set of columsn, 3 means as many columns as are available.
session : object
optional session to use for network requests
**keywords :
additional parameters can be given via arbitrary
case insensitive keyword arguments. Where there is overlap
with the parameters set by the other arguments to
this function, these keywords will override.
"""
super().__init__(baseurl, session=session, **keywords)
if pos is not None:
self.pos = pos
if size is not None:
self.size = size
if format is not None:
self.format = format
if intersect is not None:
self.intersect = intersect
if verbosity is not None:
self.verbosity = verbosity
@property
def pos(self):
"""
the position of the center of the rectangular search region as a
`~astropy.coordinates.SkyCoord` instance.
"""
return getattr(self, "_pos", None)
@pos.setter
def pos(self, pos):
setattr(self, "_pos", pos)
if not isinstance(pos, SkyCoord):
try:
ra, dec = pos
except (TypeError, ValueError):
raise ValueError(
'Pos must be a sequence with exactly two values, '
'expressing ra and dec in icrs degrees'
)
# assume degrees
pos = SkyCoord(ra=ra, dec=dec, unit="deg", frame="icrs")
self["POS"] = "{ra},{dec}".format(
ra=pos.icrs.ra.deg, dec=pos.icrs.dec.deg)
@pos.deleter
def pos(self):
delattr(self, "_pos")
del self["POS"]
@property
def size(self):
"""
the size of the rectangular region around pos as a
`~astropy.units.Quantity` instance.
"""
return getattr(self, "_size", None)
@size.setter
def size(self, size):
setattr(self, "_size", size)
if not isinstance(size, Quantity):
valerr = ValueError(
'Size must be either a single value or a sequence with two'
'values, expressing degrees'
)
try:
# assume degrees
size = size * Unit("deg")
except ValueError:
raise valerr
try:
if len(size) > 2:
raise valerr
except TypeError:
pass # len 1
try:
self["SIZE"] = ",".join(
str(deg) for deg in size.to(Unit("deg")).value)
except TypeError:
self["SIZE"] = str(size.to(Unit("deg")).value)
@size.deleter
def size(self):
delattr(self, "_size")
del self["SIZE"]
@property
def format(self):
"""
the image format(s) of interest. "all" (default)
indicates all available formats; "graphic" indicates
graphical images (e.g. jpeg, png, gif; not FITS);
"metadata" indicates that no images should be
returned--only an empty table with complete metadata;
"image/\\*" indicates a particular image format where
* can have values like "fits", "jpeg", "png", etc.
"""
return getattr(self, "_format", None)
@format.setter
def format(self, format_):
setattr(self, "_format", format_)
if isinstance(format_, (str, bytes)):
format_ = [format_]
self["FORMAT"] = ",".join(_.upper() for _ in format_)
@format.deleter
def format(self):
delattr(self, "_format")
del self["FORMAT"]
@property
def intersect(self):
"""
a token indicating how the returned images should
intersect with the search region; recognized values include:
========= ======================================================
COVERS select images that completely cover the search region
ENCLOSED select images that are complete enclosed by the region
OVERLAPS select any image that overlaps with the search region
CENTER select images whose center is within the search region
========= ======================================================
"""
return getattr(self, "_intersect", None)
@intersect.setter
def intersect(self, intersect):
setattr(self, "_intersect", intersect)
self["INTERSECT"] = intersect.upper()
@intersect.deleter
def intersect(self):
delattr(self, "_intersect")
del self["INTERSECT"]
@property
def verbosity(self):
"""
an integer value that indicates the volume of columns
to return in the result table. 0 means the minimum
set of columsn, 3 means as many columns as are available.
"""
return getattr(self, "_verbosity", None)
@verbosity.setter
def verbosity(self, verbosity):
setattr(self, "_verbosity", verbosity)
self["VERB"] = verbosity
@verbosity.deleter
def verbosity(self):
delattr(self, "_verbosity")
del self["VERB"]
[docs] def execute(self):
"""
submit the query and return the results as a SIAResults instance
Raises
------
DALServiceError
for errors connecting to or communicating with the service
DALQueryError
for errors either in the input query syntax or
other user errors detected by the service
DALFormatError
for errors parsing the VOTable response
"""
return SIAResults(self.execute_votable(), url=self.queryurl, session=self._session)
[docs]class SIAResults(DatalinkResultsMixin, DALResults):
"""
The list of matching images resulting from an image (SIA) query.
Each record contains a set of metadata that describes an available
image matching the query constraints. The number of records in
the results is available by passing it to the Python built-in ``len()`` function.
This class supports iterable semantics; thus,
individual records (in the form of
:py:class:`~pyvo.dal.sia.SIARecord` instances) are typically
accessed by iterating over an ``SIAResults`` instance.
Alternatively, records can be accessed randomly via
:py:meth:`getrecord` or through a Python Database API (v2)
Cursor (via :py:meth:`~pyvo.dal.DALResults.cursor`).
Column-based data access is possible via the
:py:meth:`~pyvo.dal.DALResults.getcolumn` method.
``SIAResults`` is essentially a wrapper around an Astropy
:py:mod:`~astropy.io.votable`
:py:class:`~astropy.io.votable.tree.TableElement` instance where the
columns contain the various metadata describing the images.
One can access that VOTable directly via the
:py:attr:`~pyvo.dal.DALResults.votable` attribute. Thus,
when one retrieves a whole column via
:py:meth:`~pyvo.dal.DALResults.getcolumn`, the result is
a Numpy array. Alternatively, one can manipulate the results
as an Astropy :py:class:`~astropy.table.table.Table` via the
following conversion:
``table = results.votable.to_table()``
``SIAResults`` supports the array item operator ``[...]`` in a
read-only context. When the argument is numerical, the result
is an
:py:class:`~pyvo.dal.sia.SIARecord` instance, representing the
record at the position given by the numerical index. If the
argument is a string, it is interpreted as the name of a column,
and the data from the column matching that name is returned as
a Numpy array.
"""
[docs] def getrecord(self, index):
"""
return a representation of a sia result record that follows
dictionary semantics. The keys of the dictionary are those returned by
this instance's fieldnames attribute. The returned record has
additional image-specific properties
Parameters
----------
index : int
the integer index of the desired record where 0 returns the first
record
Returns
-------
SIARecord
a dictionary-like wrapper containing the result record metadata.
Raises
------
IndexError
if index is negative or equal or larger than the number of rows in
the result table.
See Also
--------
Record
"""
return SIARecord(self, index, session=self._session)
[docs]class SIARecord(SodaRecordMixin, DatalinkRecordMixin, Record):
"""
a dictionary-like container for data in a record from the results of an
image (SIA) search, describing an available image.
The commonly accessed metadata which are stadardized by the SIA
protocol are available as attributes. If the metadatum accessible
via an attribute is not available, the value of that attribute
will be None. All metadata, including non-standard metadata, are
acessible via the ``get(`` *key* ``)`` function (or the [*key*]
operator) where *key* is table column name.
"""
@property
def pos(self):
"""
the position of the object or observation described by this record.
"""
return SkyCoord(
ra=self.getbyucd("POS_EQ_RA_MAIN"),
dec=self.getbyucd("POS_EQ_DEC_MAIN"),
unit="deg", frame="icrs")
# Image Metadata
@property
def title(self):
"""
the title of the image
"""
return self.getbyucd("VOX:Image_Title", decode=True)
@property
def instr(self):
"""
the name of the instrument (or instruments) that produced the data that
went into this image.
"""
return self.getbyucd("INST_ID", decode=True)
@property
def dateobs(self):
"""
the modified Julien date (MJD) of the mid-point of the
observational data that went into the image,
as an astropy.time.Time instance
"""
dateobs = self.getbyucd("VOX:Image_MJDateObs")
if dateobs:
return Time(dateobs, format="mjd")
else:
return None
@property
def naxes(self):
"""
the number of axes in this image.
"""
return self.getbyucd("VOX:Image_Naxes")
@property
def naxis(self):
"""
the lengths of the sides along each axis, in pix,
as a astropy Quantity pix
"""
return self.getbyucd("VOX:Image_Naxis") * Unit("pix")
@property
def scale(self):
"""
the scale of the pixels in each image axis, in degrees/pixel,
as a astropy Quantity deg / pix
"""
return self.getbyucd("VOX:Image_Scale") * (Unit("deg") / Unit("pix"))
@property
def format(self):
"""
the format of the image
"""
return self.getbyucd("VOX:Image_Format", decode=True)
# Coordinate System Metadata
@property
def coord_frame(self):
"""
the coordinate system reference frame, one of the following:
"ICRS", "FK5", "FK4", "ECL", "GAL", and "SGAL".
"""
return self.getbyucd("VOX:STC_CoordRefFrame", decode=True)
@property
def coord_equinox(self):
"""
the equinox of the used coordinate system
"""
return self.getbyucd("VOX:STC_CoordEquinox")
@property
def coord_projection(self):
"""
the celestial projection (TAN / ARC / SIN / etc.)
"""
return self.getbyucd("VOX:WCS_CoordProjection", decode=True)
@property
def coord_refpixel(self):
"""
the image pixel coordinates of the WCS reference pixel
"""
return self.getbyucd("VOX:WCS_CoordRefPixel")
@property
def coord_refvalue(self):
"""
the world coordinates of the WCS reference pixel.
"""
return self.getbyucd("VOX:WCS_CoordRefValue")
@property
def cdmatrix(self):
"""
the WCS CD matrix defining the scale and rotation (among other things)
of the image. ordered as CD[i,j] = [0,0], [0,1], [1,0], [1,1].
"""
return self.getbyucd("VOX:WCS_CDMatrix").reshape((2, 2))
# Spectral Bandpass Metadata
@property
def bandpass_id(self):
"""
the bandpass by name (e.g., "V", "SDSS_U", "K", "K-Band", etc.)
"""
return self.getbyucd("VOX:BandPass_ID", decode=True)
@property
def bandpass_unit(self):
"""
the astropy unit used to represent spectral values.
"""
sia = self.getbyucd("VOX:BandPass_Unit", decode=True)
if sia:
return Unit(sia)
else:
# dimensionless
return Unit("")
@property
def bandpass_refvalue(self):
"""
the characteristic (reference) wavelength, frequency or energy
for the bandpass model, as an astropy Quantity of bandpass_unit
"""
return Quantity(
self.getbyucd("VOX:BandPass_RefValue"), self.bandpass_unit)
@property
def bandpass_hilimit(self):
"""
the upper limit of the bandpass as astropy Quantity in bandpass_unit
"""
return Quantity(
self.getbyucd("VOX:BandPass_HiLimit"), self.bandpass_unit)
@property
def bandpass_lolimit(self):
"""
the lower limit of the bandpass as astropy Quantity in bandpass_unit
"""
return Quantity(
self.getbyucd("VOX:BandPass_LoLimit"), self.bandpass_unit)
# Processig Metadata
@property
def pixflags(self):
"""
the type of processing done by the image service to produce an output
image pixel
a string of one or more of the following values:
* C -- The image pixels were copied from a source image without change,
as when an atlas image or cutout is returned.
* F -- The image pixels were computed by resampling an existing image,
e.g., to rescale or reproject the data,
and were filtered by an interpolator.
* X -- The image pixels were computed by the service directly from a
primary data set hence were not filtered by an interpolator.
* Z -- The image pixels contain valid flux (intensity) values, e.g., if
the pixels were resampled with a flux-preserving interpolator.
* V -- The image pixels contain some unspecified visualization of the
data, hence are suitable for display but not for numerical
analysis.
"""
return self.getbyucd("VOX:Image_PixFlags", decode=True)
# Access Metadata
@property
def acref(self):
"""
the URL that can be used to retrieve the image
"""
return self.getbyucd("VOX:Image_AccessReference", decode=True)
@property
def acref_ttl(self):
"""
the minimum time to live in seconds of the access reference
"""
return self.getbyucd("VOX:Image_AccessRefTTL")
@property
def filesize(self):
"""
the (estimated) size of the image in bytes
"""
return self.getbyucd("VOX:Image_FileSize")
[docs] def getdataurl(self):
"""
return the URL contained in the access URL column which can be used
to retrieve the dataset described by this record. None is returned
if no such column exists.
"""
if self.acref is not None:
return self.acref
else:
return super().getdataurl()
[docs] def suggest_dataset_basename(self):
"""
return a default base filename that the dataset available via
``getdataset()`` can be saved as. This function is
specialized for a particular service type this record originates from
so that it can be used by ``cachedataset()`` via
``make_dataset_filename()``.
"""
out = self.title
if isinstance(out, bytes):
out = out.decode('utf-8')
if not out:
out = "image"
else:
out = re.sub(r'\s+', '_', out.strip())
return out
[docs] def suggest_extension(self, *, default=None):
"""
returns a recommended filename extension for the dataset described
by this record. Typically, this would look at the column describing
the format and choose an extension accordingly.
"""
return mime2extension(self.format, default)
[docs] def broadcast_samp(self, *, client_name=None):
"""
Broadcast the image to ``client_name`` via SAMP
"""
with samp.connection() as conn:
samp.send_image_to(
conn, self.getdataurl(), client_name,
name=self.suggest_dataset_basename())