Closes #57

glymur/jp2k.py

@@ -142,7 +142,7 @@ class Jp2k(Jp2kBox):
     def write(self, img_array, cratios=None, eph=False, psnr=None, numres=None,
               cbsize=None, psizes=None, grid_offset=None, sop=False,
               subsam=None, tilesize=None, prog=None, modesw=None,
-              colorspace=None, verbose=False):
+              colorspace=None, verbose=False, mct=None):
         """Write image data to a JP2/JPX/J2k file.  Intended usage of the
         various parameters follows that of OpenJPEG's opj_compress utility.
 
@@ -168,6 +168,9 @@ class Jp2k(Jp2kBox):
             If true, write SOP marker after each header packet.
         grid_offset : tuple, optional
             Offset (DY, DX) of the origin of the image in the reference grid.
+        mct : bool, optional
+            Specifies usage of the multi component transform.  If not
+            specified, defaults to True if the colorspace is RGB.
         modesw : int, optional
             Mode switch.
                 1 = BYPASS(LAZY)
@@ -337,6 +340,18 @@ class Jp2k(Jp2kBox):
             else:
                 colorspace = _cspace_map[colorspace]
 
+        if mct is None:
+            if colorspace == opj2._CLRSPC_SRGB:
+                cparams.tcp_mct = 1
+            else:
+                cparams.tcp_mct = 0
+        else:
+            if mct and colorspace == opj2._CLRSPC_GRAY:
+                msg = "Cannot specify usage of the multi component transform "
+                msg += "if the colorspace is gray."
+                raise IOError(msg)
+            cparams.tcp_mct = 1 if mct else 0
+
         if img_array.dtype == np.uint8:
             comp_prec = 8
         elif img_array.dtype == np.uint16:
@@ -373,12 +388,6 @@ class Jp2k(Jp2kBox):
             src = layer.ctypes.data
             ctypes.memmove(dest, src, layer.nbytes)
 
-        # set multi-component transform?
-        if image.contents.numcomps == 3:
-            cparams.tcp_mct = 1
-        else:
-            cparams.tcp_mct = 0
-
         codec = opj2._create_compress(codec_fmt)
 
         if verbose:
@@ -435,6 +444,11 @@ class Jp2k(Jp2kBox):
         jp2h_lst = [idx for (idx, box) in enumerate(boxes) if box.id == 'jp2h']
         jp2h_idx = jp2h_lst[0]
         jp2c_lst = [idx for (idx, box) in enumerate(boxes) if box.id == 'jp2c']
+        if len(jp2c_lst) == 0:
+            msg = "A codestream box must be defined in the outermost "
+            msg += "list of boxes."
+            raise IOError(msg)
+
         jp2c_idx = jp2c_lst[0]
         if jp2h_idx >= jp2c_idx:
             msg = "The codestream box must be preceeded by a jp2 header box."

glymur/test/test_jp2box.py

@@ -310,6 +310,24 @@ class TestJp2Boxes(unittest.TestCase):
             with self.assertRaises(IOError):
                 j2k.wrap(tfile.name, boxes=boxes)
 
+    def test_missing_codestream(self):
+        j2k = Jp2k(self.raw_codestream)
+        c = j2k.get_codestream()
+        height = c.segment[1].Ysiz
+        width = c.segment[1].Xsiz
+        num_components = len(c.segment[1].XRsiz)
+
+        jP = JPEG2000SignatureBox()
+        ftyp = FileTypeBox()
+        jp2h = JP2HeaderBox()
+        ihdr = ImageHeaderBox(height=height, width=width,
+                              num_components=num_components)
+        jp2h.box = [ihdr]
+        boxes = [jP, ftyp, jp2h]
+        with tempfile.NamedTemporaryFile(suffix=".jp2") as tfile:
+            with self.assertRaises(IOError):
+                j2k.wrap(tfile.name, boxes=boxes)
+
     def test_missing_colr_box(self):
         j2k = Jp2k(self.raw_codestream)
         c = j2k.get_codestream()

glymur/test/test_jp2k.py

@@ -76,6 +76,8 @@ class TestJp2k(unittest.TestCase):
     def setUp(self):
         self.jp2file = pkg_resources.resource_filename(glymur.__name__,
                                                        "data/nemo.jp2")
+        self.j2kfile = pkg_resources.resource_filename(glymur.__name__,
+                                                       "data/goodstuff.j2k")
 
     def tearDown(self):
         pass
@@ -152,6 +154,27 @@ class TestJp2k(unittest.TestCase):
         subsetdata = j.read(area=(0, 0, 512, 512))
         np.testing.assert_array_equal(tiledata, subsetdata)
 
+    def test_write_srgb_without_mct(self):
+        j2k = Jp2k(self.j2kfile)
+        expdata = j2k.read()
+        with tempfile.NamedTemporaryFile(suffix='.jp2') as tfile:
+            ofile = Jp2k(tfile.name, 'wb')
+            ofile.write(expdata, mct=False)
+            actdata = ofile.read()
+            np.testing.assert_array_equal(actdata, expdata)
+
+            c = ofile.get_codestream()
+            self.assertEqual(c.segment[2].SPcod[3], 0)  # no mct
+
+    def test_write_grayscale_with_mct(self):
+        # MCT usage makes no sense for grayscale images.
+        j2k = Jp2k(self.j2kfile)
+        expdata = j2k.read()
+        with tempfile.NamedTemporaryFile(suffix='.jp2') as tfile:
+            ofile = Jp2k(tfile.name, 'wb')
+            with self.assertRaises(IOError):
+                ofile.write(expdata[:,:,0], mct=True)
+
     def test_write_cprl(self):
         # Issue 17
         j = Jp2k(self.jp2file)