Erroring out appropriately when _read_openjpeg gets differing sampling

If the subsampling factors are different, we should error out when using
read with libopenjpeg.  Closed #72

glymur/jp2k.py

@@ -613,9 +613,19 @@ class Jp2k(Jp2kBox):
 
         Raises
         ------
-        IOError
+        RuntimeError
             If the image has differing subsample factors.
         """
+        # Check for differing subsample factors.
+        codestream = self.get_codestream(header_only=True)
+        dxs = np.array(codestream.segment[1].XRsiz)
+        dys = np.array(codestream.segment[1].YRsiz)
+        if np.any(dxs - dxs[0]) or np.any(dys - dys[0]):
+            msg = "Components must all have the same subsampling factors "
+            msg += "to use this method with OpenJPEG 1.5.1.  Please consider "
+            msg += "using OPENJP2 instead."
+            raise RuntimeError(msg)
+
 
         with ExitStack() as stack:
             # Set decoding parameters.
@@ -653,7 +663,6 @@ class Jp2k(Jp2kBox):
             stack.callback(opj._cio_close, cio)
 
             ncomps = image.contents.numcomps
-
             component = image.contents.comps[0]
             if component.sgnd:
                 if component.prec <= 8:
@@ -726,7 +735,7 @@ class Jp2k(Jp2kBox):
 
         Raises
         ------
-        IOError
+        RuntimeError
             If the image has differing subsample factors.
         """
         # Check for differing subsample factors.
@@ -735,7 +744,7 @@ class Jp2k(Jp2kBox):
         dys = np.array(codestream.segment[1].YRsiz)
         if np.any(dxs - dxs[0]) or np.any(dys - dys[0]):
             msg = "Components must all have the same subsampling factors."
-            raise IOError(msg)
+            raise RuntimeError(msg)
 
         img_array = self._read_common(reduce=reduce,
                                       layer=layer,

glymur/test/test_jp2k.py

@@ -319,7 +319,7 @@ class TestJp2k(unittest.TestCase):
         # Issue 86.
         filename = os.path.join(data_root, 'input/conformance/p0_05.j2k')
         j = Jp2k(filename)
-        with self.assertRaises(IOError):
+        with self.assertRaises(RuntimeError):
             j.read()
 
     @unittest.skipIf(data_root is None,

glymur/test/test_jp2k_15.py

@@ -794,12 +794,11 @@ class TestSuite(unittest.TestCase):
         data = Jp2k(jfile).read()
         self.assertTrue(True)
 
-    @unittest.skip("Should have worked, must be investigated.")
     def test_NR_DEC_file_409752_jp2_40_decode(self):
         jfile = os.path.join(data_root, 'input/nonregression/file409752.jp2')
         j = Jp2k(jfile)
-        data = j.read()
-        self.assertTrue(True)
+        with self.assertRaises(RuntimeError) as ce:
+            data = j.read()
 
 if __name__ == "__main__":
     unittest.main()

glymur/test/test_opj_suite.py

@@ -1068,7 +1068,7 @@ class TestSuite(unittest.TestCase):
     def test_NR_DEC_file_409752_jp2_40_decode(self):
         jfile = os.path.join(data_root,
                              'input/nonregression/file409752.jp2')
-        with self.assertRaises(IOError):
+        with self.assertRaises(RuntimeError):
             data = Jp2k(jfile).read()
 
     @unittest.skipIf(sys.hexversion < 0x03020000,