From 408681d0803c0632e21d6d9f94664f75938106dd Mon Sep 17 00:00:00 2001
From: "Erik M. Bray" <embray@stsci.edu>
Date: Tue, 16 Sep 2014 18:37:11 -0400
Subject: [PATCH] Fixes #2710

---
 CHANGES.rst                         |  4 ++++
 astropy/io/fits/hdu/image.py        |  5 ++++-
 astropy/io/fits/tests/test_image.py | 18 ++++++++++++++++++
 3 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/CHANGES.rst b/CHANGES.rst
index 77ed81b879b..15abed3ada0 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -260,6 +260,10 @@ Bug Fixes
 
 - ``astropy.io.fits``
 
+  - Fixed a crash when reading scaled float data out of a FITS file that was
+    loaded from a string (using ``HDUList.fromfile``) rather than from a file.
+    [#2710]
+
   - Fixed a crash when reading data from an HDU whose header contained in
     invalid value for the BLANK keyword (eg. a string value instead of an
     integer as required by the FITS Standard). Invalid BLANK keywords are now
diff --git a/astropy/io/fits/hdu/image.py b/astropy/io/fits/hdu/image.py
index f382aa93036..3cfb4bfc50f 100644
--- a/astropy/io/fits/hdu/image.py
+++ b/astropy/io/fits/hdu/image.py
@@ -616,7 +616,10 @@ def _get_scaled_image_data(self, offset, shape):
             if new_dtype is not None:
                 data = np.array(raw_data, dtype=new_dtype)
             else:  # floating point cases
-                if self._file.memmap:
+                if self._file is not None and self._file.memmap:
+                    data = raw_data.copy()
+                elif not raw_data.flags.writeable:
+                    # create a writeable copy if needed
                     data = raw_data.copy()
                 # if not memmap, use the space already in memory
                 else:
diff --git a/astropy/io/fits/tests/test_image.py b/astropy/io/fits/tests/test_image.py
index 4cef8911930..7983b8068f1 100644
--- a/astropy/io/fits/tests/test_image.py
+++ b/astropy/io/fits/tests/test_image.py
@@ -809,6 +809,24 @@ def test_invalid_blank(self):
         msg = "Invalid 'BLANK' keyword"
         assert msg in str(w[1].message)
 
+    def test_scaled_image_fromfile(self):
+        """
+        Regression test for https://github.com/astropy/astropy/issues/2710
+        """
+
+        # Make some sample data
+        a = np.arange(100, dtype=np.float32)
+
+        hdu = fits.PrimaryHDU(data=a.copy())
+        hdu.scale(bscale=1.1)
+        hdu.writeto(self.temp('test.fits'))
+
+        with open(self.temp('test.fits'), 'rb') as f:
+            file_data = f.read()
+
+        hdul = fits.HDUList.fromstring(file_data)
+        assert np.allclose(hdul[0].data, a)
+
 
 class TestCompressedImage(FitsTestCase):
     def test_empty(self):