@@ -119,10 +119,10 @@
 See :mod:`nibabel.minc1`, :mod:`nibabel.ecat` and :mod:`nibabel.parrec` for
 examples.
 """
-
 _default_order = 'F'
 
-def __init__(self, file_like, spec, *, mmap=True, order=None, keep_file_open=None):
+def __init__(self, file_like, spec, *,
+mmap=True, order=None, keep_file_open=None, compression=None):
 """Initialize array proxy instance
 
 Parameters
@@ -166,6 +166,7 @@
 If ``file_like`` is an open file handle, this setting has no
 effect. The default value (``None``) will result in the value of
 ``KEEP_FILE_OPEN_DEFAULT`` being used.
+compression : { None, "gz", "bz2", "zst" }, optional, keyword only
 """
 if mmap not in (True, False, 'c', 'r'):
 raise ValueError("mmap should be one of {True, False, 'c', 'r'}")
@@ -209,9 +210,11 @@
 if order is None:
 order = self._default_order
 self.order = order
+self._compression = compression
 # Flags to keep track of whether a single ImageOpener is created, and
 # whether a single underlying file handle is created.
-self._keep_file_open, self._persist_opener = self._should_keep_file_open(keep_file_open)
+self._keep_file_open, self._persist_opener = \
+self._should_keep_file_open(keep_file_open, compression)
 self._lock = RLock()
 
 def _has_fh(self) -> bool:
@@ -254,7 +257,7 @@
 self.__dict__.update(state)
 self._lock = RLock()
 
-def _should_keep_file_open(self, keep_file_open):
+def _should_keep_file_open(self, keep_file_open, compression):
 """Called by ``__init__``.
 
 This method determines how to manage ``ImageOpener`` instances,
@@ -330,7 +333,8 @@
 if self._has_fh():
 return False, False
 # if the file is a gzip file, and we have_indexed_gzip,
-have_igzip = openers.HAVE_INDEXED_GZIP and self.file_like.endswith('.gz')
+have_igzip = openers.HAVE_INDEXED_GZIP and (compression in ("gz", ".gz") or
+file_like.endswith('.gz'))
 
 persist_opener = keep_file_open or have_igzip
 return keep_file_open, persist_opener
@@ -378,10 +382,18 @@
 """
 if self._persist_opener:
 if not hasattr(self, '_opener'):
-self._opener = openers.ImageOpener(self.file_like, keep_open=self._keep_file_open)
+self._opener = openers.ImageOpener(
+self.file_like,
+keep_open=self._keep_file_open,
+compression=self._compression,
+)
 yield self._opener
 else:
-with openers.ImageOpener(self.file_like, keep_open=False) as opener:
+with openers.ImageOpener(
+self.file_like,
+keep_open=False,
+compression=self._compression,
+) as opener:
 yield opener
 
 def _get_unscaled(self, slicer):

@@ -124,6 +124,7 @@
 specified, is `rb`. ``compresslevel``, if relevant, and not specified,
 is set from class variable ``default_compresslevel``. ``keep_open``, if
 relevant, and not specified, is ``False``.
+compression : { None, "gz", "bz2", "zst" }, optional, keyworld only
 \*\*kwargs : keyword arguments
 passed to opening method when `fileish` is str. Change of defaults as
 for \*args
@@ -153,13 +154,13 @@
 
 fobj: io.IOBase
 
-def __init__(self, fileish: str | io.IOBase, *args, **kwargs):
+def __init__(self, fileish: str | io.IOBase, *args, compression: str | None = None, **kwargs):
 if isinstance(fileish, (io.IOBase, Fileish)):
 self.fobj = fileish
 self.me_opened = False
 self._name = getattr(fileish, 'name', None)
 return
-opener, arg_names = self._get_opener_argnames(fileish)
+opener, arg_names = self._get_opener_argnames(fileish, compression)
 # Get full arguments to check for mode and compresslevel
 full_kwargs = {**kwargs, **dict(zip(arg_names, args))}
 # Set default mode
@@ -183,7 +184,11 @@
 self._name = fileish
 self.me_opened = True
 
-def _get_opener_argnames(self, fileish: str) -> OpenerDef:
+def _get_opener_argnames(self, fileish: str, compression: str | None) -> OpenerDef:
+if compression is not None:
+if compression[0] != '.':
+compression = f'.{compression}'
+return self.compress_ext_map[compression]
 _, ext = splitext(fileish)
 if self.compress_ext_icase:
 ext = ext.lower()